Sensor device capable of measuring electric field strength, method for manufacturing the sensor device, and method for measuring electric field strength

Abstract

The present invention provides a highly sensitive sensor device for measuring an external electric field, which has a dielectric layer that allows for greater carrier movement between the channel layer and the dielectric layer. [Solution] The sensor device is a sensor device capable of measuring the electric field strength of an external electric field. The sensor device comprises a dielectric layer having a first surface and a second surface, a channel layer disposed on the second surface of the dielectric layer and having a channel region, and a first electrode and a second electrode disposed on the channel layer so as to face each other across the channel region. The dielectric layer is manufactured such that vacancies are formed on the second surface by passing a current through it, or by irradiating the second surface with radiation, thereby increasing the number of carrier trap levels on the second surface.

Description

[Technical Field]

[0001] The present invention relates to a sensor device capable of measuring electric field strength, a method for manufacturing the sensor device, and a method for measuring electric field strength. [Background technology]

[0002] Conventionally, sensor devices have been used to measure the electric field strength in the atmosphere. By measuring the electric field strength in the atmosphere, the formation and movement of thunderclouds are monitored.

[0003] Furthermore, sensor devices are used to measure the electric field strength in the atmosphere indoors. By measuring the electric field strength, the static electricity situation in the room is monitored, which helps prevent accidents caused by static electricity.

[0004] A sensor device using semiconductors has been proposed for measuring electric field strength (see, for example, Non-Patent Document 1). This sensor device is relatively small in size and lightweight.

[0005] A semiconductor-based sensor device has a transistor that includes graphene or the like as a channel layer. The electric field strength of the external electric field applied to the sensor device is measured as the magnitude of the current flowing between the source electrode and the drain electrode. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] WANG et al., High-performance graphene-based electrostatic field sensor, IEEE ELECTRON DEVICE LETTERS, VOL38, No. 8, 1136~1138, AUGUST 2017 [Overview of the project] [Problems that the invention aims to solve]

[0007] The sensitivity of a sensor device in measuring an external electric field is influenced by the carrier mobility and carrier density in the channel layer. Sensitivity increases with higher carrier mobility in the channel layer. Furthermore, sensitivity increases with greater change in carrier density between the application of an external electric field and the absence of an external electric field in the channel layer. Therefore, focusing on the channel layer is sometimes considered to improve the sensitivity of a sensor device in measuring an external electric field.

[0008] Furthermore, in a sensor device to which an external electric field is applied, carrier movement occurs between the dielectric layer and the channel layer. In a sensor device to which an external electric field is applied, the movement of many carriers from the dielectric layer to the channel layer increases the carrier density in the channel layer, thereby improving the sensitivity of the sensor device.

[0009] Therefore, focusing on the dielectric layer is also an effective way to improve the sensitivity of the sensor device in measuring the external electric field.

[0010] This disclosure aims to propose a highly sensitive sensor device for measuring an external electric field, which has a dielectric layer that allows for greater carrier movement between the channel layer and the dielectric layer. [Means for solving the problem]

[0011] (1) According to one embodiment of the present disclosure, a sensor device is provided. This sensor device is capable of measuring the electric field strength of an external electric field and comprises a dielectric layer having a first surface and a second surface, a channel layer disposed on the second surface of the dielectric layer and having a channel region, and a first electrode and a second electrode disposed on the channel layer so as to face each other across the channel region, wherein the dielectric layer is manufactured such that a vacancy is formed on the second surface by passing a current through the second surface, or a vacancy is formed on the second surface by irradiating the second surface with radiation, thereby increasing the number of carrier trap levels on the second surface.

[0012] (2) In the sensor device of (1), holes are formed on the second surface by passing a current through the second surface, or holes are formed on the second surface by irradiating the second surface with radiation, and the trap level density of carriers on the second surface is 10 , ―2 , 2 , 13 , 2 , , -2 , 2 ,

[0015] , -2 , , ―1 ,

[0014] , 2 , , 2 , 2 ~10 13 eV ―1 cm ―2 It is preferably increasing within the range of.

[0013] (3) In the sensor device of (1) or (2), holes are formed on the second surface by passing a current through the second surface, or holes are formed on the second surface by irradiating the second surface with radiation, and the trap level density of carriers in the range of 100 nm in the depth direction from the second surface to the first surface of the dielectric layer is 10 11 ~10 13 eV ―1 cm ―2 It is preferably increasing within the range of.

[0014] (4) In any of the sensor devices of (1) to (3), the dielectric layer preferably has a total charge amount per unit area of 0.265×10 -2 C / cm 2 ~10 C / cm 2 and a current is passed through the second surface to form holes on the second surface.

[0015] (5) In any of the sensor devices of (1) to (3), the dielectric layer is irradiated with electrons under conditions determined by a combination in the range of incident energy of 0.1 keV to 500 keV and a total irradiation amount per unit area of 10 -2 μC / cm 2 ~1 mC / cm 2 to form holes on the second surface, or is irradiated with ions under conditions determined by a combination in the range of incident energy of 0.5 keV to 2 MeV and a total irradiation amount per unit area of 1 μC / cm 2 ~100 mC / cm 2 to form holes on the second surface, or the irradiation amount per unit area is in the range of 1010 ~10 15 photons / cm 2 It is preferable that ultraviolet light is irradiated under conditions determined by a combination of the range and irradiation time in the range of 1 second to 1000 seconds to form voids on the second surface.

[0016] (6) In any of the sensor devices of (1) to (5), the channel layer is preferably made of one or more atomic layers of graphene, or an atomic layer material film of one or more atomic layers formed of a two-dimensional transition metal dichalcogenide.

[0017] (7) In the sensor devices of (1) to (6), the dielectric layer preferably has a thickness in the range of 90 to 300 nm.

[0018] (8) Another embodiment of the present disclosure provides a method for manufacturing a sensor device. This method for manufacturing a sensor device capable of measuring the electric field strength of an external electric field comprises: a first step of forming a dielectric layer having a first surface and a second surface on a substrate such that the second surface is exposed; a second step of forming a channel layer on the second surface of the dielectric layer; a third step of forming a first electrode and a second electrode on the channel layer so as to be spaced apart and facing each other; and a fourth step of increasing the number of carrier trap levels on the second surface by forming vacancies on the second surface of the dielectric layer by passing an electric current through the second surface or by irradiating the second surface with radiation, wherein the fourth step is performed between the first and second steps, or the formation of vacancies on the second surface by passing an electric current through the second surface of the dielectric layer in the fourth step is performed after the third step.

[0019] In the manufacturing method of the sensor device described in (9)(8), in the fourth step, the total charge per unit area is 0.265 × 10 -2 C / cm 2 ~10°C / cm 2 Within this range, it is preferable that the current flows through the second surface of the dielectric layer.

[0020] In the method for manufacturing the sensor device of (10)(8) or (9), in the fourth step, the incident energy is in the range of 0.1 keV to 500 keV and the total irradiation amount per unit area is 10 -2 μC / cm 2 ~1 mC / cm 2 The electrons are irradiated under conditions determined by a combination of the following ranges, or the incident energy is in the range of 0.5 keV to 2 MeV and the total irradiation dose per unit area is 1 μC / cm². 2 ~100mC / cm 2 Ions are irradiated under conditions determined by a combination of the following ranges, or the incident energy is in the range of 4eV to 50eV, and the irradiation dose per unit area is 10 10 ~10 15 photons / cm 2 It is preferable that ultraviolet light is irradiated under conditions determined by a combination of the range and irradiation time, which range from 1 second to 1000 seconds.

[0021] In the manufacturing method of the sensor device described in (11)(8)~(10), in the fourth step, the carrier trap level density on the second surface is 10 11 ~10 13 eV ―1 cm ―3 It is preferable to increase within the range of [value].

[0022] In the manufacturing method of the sensor device described in (12)(8)~(11), in the fourth step, the carrier trap level density in the 100 nm depth range from the second surface to the first surface of the dielectric layer is 10 11 ~10 13 eV ―1 cm ―3 It is preferable to increase within the range of [value].

[0023] (13) Another embodiment of the present disclosure provides a method for measuring an external electric field. This method for measuring an external electric field is a measurement method for measuring an external electric field using a sensor device described in any of (1) to (7), and is characterized by comprising: measuring the value of the current flowing between a first electrode and a second electrode while an external electric field is applied to the sensor device; and determining the electric field strength of the external electric field based on the current value. [Effects of the Invention]

[0024] According to the sensor device of the present disclosure described above, since it has a dielectric layer in which more carriers move between it and the channel layer, it can measure the external electric field with high sensitivity. [Brief explanation of the drawing]

[0025] [Figure 1] (A) is a cross-sectional view of a first embodiment of the sensor device disclosed herein, and (B) is a plan view. [Figure 2] This diagram illustrates the movement of carriers between the channel layer and the dielectric layer. [Figure 3] This figure shows the relationship between electron energy and density of states in the channel layer. [Figure 4] (A) is a diagram showing the relationship between energy levels when the channel layer and the dielectric layer are separated, and (B) is a diagram showing the relationship between energy levels when the channel layer and the dielectric layer are in contact. [Figure 5] This diagram illustrates the current processing of a sensor device. [Figure 6] This figure shows the state in which a negative external electric field is applied to the sensor device. [Figure 7] This figure shows the relationship between the drain current and gate voltage of the sensor device. [Figure 8] This diagram illustrates the measurement of an external electric field using a sensor device. [Figure 9] This figure shows the relationship between the responsiveness of the sensor device and the electric field strength of the external electric field. [Figure 10]This figure shows the relationship between the responsiveness of the sensor device and the current processing time. [Figure 11] This figure shows a second embodiment of the sensor device disclosed herein. [Figure 12] This figure shows a third embodiment of the sensor device disclosed herein. [Figure 13] (A) and (B) are diagrams (1) showing the manufacturing process of a first embodiment of the method for manufacturing a sensor device disclosed herein. [Figure 14] (A) and (B) are diagrams (part 2) showing the manufacturing process of the first embodiment of the method for manufacturing a sensor device disclosed herein. [Figure 15] (A) and (B) are diagrams showing the manufacturing process of a modified example of the first embodiment of the method for manufacturing a sensor device disclosed herein. [Figure 16] This figure shows the manufacturing process of a second embodiment of the method for manufacturing a sensor device disclosed herein. [Figure 17] This figure shows the relationship between the responsiveness of the sensor devices in the examples and comparative examples and the electric field strength of the external electric field. [Modes for carrying out the invention]

[0026] A preferred first embodiment of the sensor device disclosed herein will be described below with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and its equivalents.

[0027] Figure 1(A) shows a first embodiment of the sensor device 10 disclosed herein. Figure 1(A) shows a state in which a positive external electric field is applied to the sensor device 10 from the outside. Figure 1(B) is a plan view of the sensor device. Figure 1(A) is a cross-sectional view taken along the line X1-X1 in Figure 1(B).

[0028] The sensor device 10 of this embodiment is capable of measuring the electric field strength of an external electric field E applied from the outside. The external electric field E refers to the electric field generated from a source located outside the sensor device 10. Since the sensor device 10 has high sensitivity, it is capable of measuring even small electric field strengths.

[0029] The sensor device 10 includes a substrate 11, a dielectric layer 12, a channel layer 13, a source electrode 14, and a drain electrode 15. The sensor device 10 of this embodiment is capable of measuring the magnitude of an external electric field E as a current.

[0030] The substrate 11 preferably has mechanical strength to support other components of the sensor device 10. The substrate 11 has a first surface 11A and a second surface 11B. As the substrate 11, for example, a semiconductor substrate such as a silicon substrate, silicon carbide, or compound semiconductor can be used. As the semiconductor substrate, an amorphous, polycrystalline, or single-crystal substrate can be used. The substrate 11 may have p-type polarity or n-type polarity. Furthermore, the substrate 11 may be intrinsic without added impurities. Note that if the dielectric layer 12 has mechanical strength to support other components of the sensor device 10, the sensor device 10 does not need to have the substrate 11.

[0031] The dielectric layer 12 has electrical insulating properties and is disposed on the second surface 11B of the substrate 11. The dielectric layer 12 electrically insulates the substrate 11 from the channel layer 13. The dielectric layer 12 has a first surface 12A and a second surface 12B. The first surface 12A faces the substrate 11, and the second surface 12B faces the channel layer 13.

[0032] As the dielectric layer 12, dielectric materials such as silicon dioxide (SiO2), aluminum oxide, hafnium dioxide, or silicon nitride can be used. Amorphous, polycrystalline, or single-crystal dielectric layers 12 can be used. When the substrate 11 is a silicon substrate, using silicon dioxide as the dielectric layer 12 is preferable from the viewpoint of easily manufacturing the sensor device 10.

[0033] At the interface between the dielectric layer 12 and the channel layer 13, trap levels capable of trapping carriers exist due to defects or impurities. Examples of defects include vacancies and interstitial atoms. Carriers include electrons and holes.

[0034] When an external charge E1 is applied to the sensor device 10, carrier movement occurs between the trap levels of the dielectric layer 12 and the channel layer 13, increasing the carrier density of the channel layer 13. This increase in carrier density also improves the sensitivity of the sensor device 10.

[0035] The dielectric layer 12 is manufactured such that, after being formed on the substrate 11, vacancies are formed on the second surface 12B by passing an electric current through the second surface 12B (hereinafter also referred to as current treatment), or by irradiating the second surface 12B with radiation (hereinafter also referred to as irradiation treatment), thereby increasing the number of carrier trap levels on the second surface 12B. It is preferable that interstitial atoms are also formed along with vacancies by the current treatment or irradiation treatment. In this specification, radiation includes charged particles (ions) and electromagnetic waves.

[0036] At the time the dielectric layer 12 is formed on the substrate 11, trap levels exist on the second surface 12B of the dielectric layer 12. By further increasing the number of trap levels through current processing or irradiation processing, the sensitivity of the sensor device 10 is further improved.

[0037] Here, the carrier trap level density on the second surface 12B may refer to the trap level density per unit area of ​​the second surface 12B of the dielectric layer 12. Alternatively, the carrier trap level density on the second surface 12B may refer to the trap level density per unit volume in the vicinity of the second surface 12B of the dielectric layer 12. The vicinity of the second surface 12B refers to the region including the second surface 12B and its interior. For example, the vicinity of the second surface 12B includes a 100 nm portion in the depth direction from the second surface 12B toward the first surface 12A.

[0038] Thus, it is preferable that the sensor device 10 of this embodiment includes a manufacturing process as part of its configuration. The reasons why the sensor device of this embodiment includes a manufacturing process as part of its features will be explained below. The difference between the sensor device of this embodiment and the prior art is that the second surface 12B of the dielectric layer 12 has many carrier trap levels. However, given the non-uniformity of the dielectric layer 12, it can be said that it is impossible to specify the structure or characteristics related to this difference in words. On the other hand, while it may be possible in principle to determine the trap levels of the second surface 12B of the dielectric layer 12 using electron microscopy observation and elemental analysis, it would be necessary to manufacture a statistically significant number of both the sensor device 10 of this embodiment and the sensor device of the prior art, obtain the results of electron microscopy observation and elemental analysis, and then statistically process them to find meaningful indicators and values ​​that distinguish this embodiment from the prior art, which would require an enormous amount of time and cost. Moreover, since there are a vast number of possibilities for the prior art, it is difficult to uniquely determine a statistically significant number. Therefore, it is not practical to identify the above-mentioned indicators and their values ​​and directly specify the characteristics of the sensor device 10 of this embodiment solely by the structure or properties of the object. Based on the above considerations, in order to define the characteristic of the trap level of the second surface 12B of the dielectric layer 12, the configuration of the sensor device of this embodiment may include a manufacturing process.

[0039] By current treatment or irradiation treatment, the carrier trap level density on the second surface 12B of the dielectric layer 12 is 10 11 ~10 13 eV ―1 cm ―2 It is preferable that it increases within the range of 10. As mentioned above, although it is difficult to define the trap level density numerically, from the viewpoint of sufficiently increasing the carrier density of the channel layer 13, 10 11 eV ―1 cm ―2 It is considered preferable that the trap level density increases above the above limit. Furthermore, from the viewpoint of maintaining the physical state of the second surface 12B of the dielectric layer 12, the upper limit of the increasing trap level density is 10 13 eV ―1cm ―2 This is considered to be the extent of the increase. The reason for this estimated increase in trap level density will be explained later.

[0040] Furthermore, by current treatment or irradiation treatment, the carrier trap level density in the 100 nm depth range from the second surface 12B to the first surface 12A of the dielectric layer 12 is 10 11 ~10 13 eV ―1 cm ―3 It is preferable that it increases within the range of 10. As mentioned above, although it is difficult to define the trap level density numerically, from the viewpoint of sufficiently increasing the carrier density of the channel layer 13, 10 11 eV ―1 cm ―3 It is considered preferable that the trap level density increases above the above limit. Furthermore, from the viewpoint of maintaining the physical state of the second surface 12B of the dielectric layer 12, the upper limit of the increasing trap level density is 10 13 eV ―1 cm ―3 This is considered to be the extent of the increase. The reason for this estimated increase in trap level density will be explained later.

[0041] The dielectric layer 12 preferably has a thickness in the range of 90 to 300 nm. This makes it easier to laminate a graphene or molybdenum disulfide layer on top of the dielectric layer 12 during the manufacturing of the sensor device 10.

[0042] The channel layer 13 has a channel region 131 and is disposed on the dielectric layer 12. The channel layer 13 has a first surface 13A and a second surface 13B. The first surface 13A is disposed on the dielectric layer 12, and at least a portion of the second surface 13B is exposed to the outside. The second surface 13B acts as an input / output region 10a into which the sensor device 10 inputs or outputs an external electric field E. It is preferable that at least the channel region 131 is disposed on the dielectric layer 12. In this embodiment, the entire channel layer 13 is disposed on the dielectric layer 12.

[0043] The channel layer 13 may have p-type polarity or n-type polarity. Furthermore, the channel layer 13 may be intrinsic, without added impurities.

[0044] The channel layer 13 may be directly placed on the dielectric layer 12. Direct placement of the channel layer 13 on the dielectric layer 12 means that substantially no other layers are placed between the channel layer 13 and the dielectric layer 12. However, the presence of an oxide layer or the like unintentionally formed on the surface of the channel layer 13 or the surface of the dielectric layer 12 is permissible.

[0045] Furthermore, other layers may be placed between the channel layer 13 and the dielectric layer 12. In this case, it is preferable that the other layer does not hinder the movement of carriers between the dielectric layer 12 and the channel layer 13 when an external electric field E is applied to the sensor device 10. The thickness of this other layer is preferably such that it does not prevent carriers from flowing as tunnel current between the dielectric layer 12 and the channel layer 13.

[0046] The source electrode 14 and the drain electrode 15 are in electrical contact with the channel layer 13 and are arranged to face each other across the channel region 131 of the channel layer 13. In this embodiment, a portion of each of the source electrode 14 and the drain electrode 15 is positioned on the channel layer 13. The source electrode 14 and the drain electrode 15 are electrically conductive. A laminate of chromium and gold can be used as the source electrode 14 and the drain electrode 15. When measuring the external electric field E using the sensor device 10, a predetermined voltage is applied between the source electrode 14 and the drain electrode 15.

[0047] Next, the dielectric layer 12 and channel layer 13 of the sensor device 10 will be further explained below.

[0048] The higher the sensitivity (gain) of the sensor device 10, the higher the lower limit of the measurable electric field strength. From the viewpoint of increasing the sensitivity of the sensor device 10, it is preferable that the carrier mobility and / or carrier density in the channel layer 13 are high.

[0049] From the viewpoint of increasing the sensitivity of the sensor device 10, it is preferable that the channel layer 13 has one or more atomic layers of graphene, or one or more atomic layer material films formed of a two-dimensional transition metal dichalcogenide.

[0050] First, the relationship between the dielectric layer 12 and the channel layer 13 will be explained below, assuming that the channel layer 13 is formed using graphene. Compared to silicon, graphene has high carrier mobility. A single atomic layer of graphene has a carrier mobility of 2 × 10⁻¹⁶. 5 (cm 2 ∨ -1 S -1 It has a carrier mobility of 1.4 × 10⁻¹⁰. This carrier mobility is 1.4 × 10⁻¹⁰ of the electron mobility in a crystalline silicon substrate. 3 (cm 2 ∨ -1 S -1 This value is more than two orders of magnitude higher than the previous value. From the viewpoint of obtaining high carrier mobility, it is preferable that the channel layer 13 be formed using 1 to 10 atomic layers of graphene, particularly 1 to 3 atomic layers. In particular, the highest carrier mobility can be obtained by forming the channel layer 13 using a single atomic layer of graphene.

[0051] Figure 2 illustrates the carrier movement between the channel layer 13 and the dielectric layer 12. The schematic diagram on the left in Figure 2 shows the electron dispersion relation of the channel layer 13 formed by graphene. Graphene has no band gap and has a vertically symmetrical band structure. The vertically symmetrical band structure is connected at the Dirac point. The Fermi level of graphene is located near the Dirac point.

[0052] The schematic diagram on the right in Figure 2 shows the relationship between the energy of the trap levels and the trap level density on the second surface 12B of the dielectric layer 12. The second surface 12B of the dielectric layer 12 forms an interface with the channel layer 13. The dielectric layer 12 has a band gap between the lower end Ec of the conduction band and the upper end Ev of the valence band of the substrate 11. A trap level band B1 consisting of multiple trap levels is formed in the band gap. The trap level density of trap level band B1 is increased compared to the trap level density of trap level band B2 before treatment by the current treatment or irradiation treatment described above.

[0053] Carriers in the channel layer 13 can move as tunnel currents between the trap levels of the dielectric layer 12, which have the same energy levels.

[0054] In the sensor device 10 to which an external electric field E is applied, carrier movement occurs between the channel layer 13 and the second surface 12B of the dielectric layer 12, increasing the carrier density of the channel layer 13. As described above, since the trap level density in the trap level band B1 is high, the carrier density of the channel layer 13 increases significantly. This makes it possible to improve the sensitivity of the sensor device 10 in measuring the external electric field E.

[0055] Next, the relationship between the dielectric layer 12 and the channel layer 13 will be described below, assuming that the channel layer 13 is formed from a two-dimensional transition metal dichalcogenide. The channel layer 13 may have one or more atomic layer material films formed from a two-dimensional transition metal dichalcogenide.

[0056] The channel layer 13 preferably contains molybdenum (Mo), tungsten (W), or niobium (Nb) as a transition metal. The channel layer 13 preferably contains sulfur (S), selenium (Se), or tellurium (Te) as a chalcogenide element. Examples of two-dimensional transition metal dichalcogenides include MoS2, MoSe2, WS2, WSe2, NbS2, and NbSe2.

[0057] Figure 3 shows the relationship between electron energy and density of states in channel layer 13. Figure 3 illustrates the relationship between electron energy and density of states in MoS2, a two-dimensional transition metal dichalcogenide, and graphene. Figure 3 shows the calculated relationship between electron energy and density of states (DOS) when channel layer 13 is MoS2. The horizontal axis in Figure 3 represents the electron energy in channel layer 13, and the vertical axis represents the electron density of states. The electron density of states represents the number of electron states per unit volume and per unit energy. In Figure 3, the electron density of states is shown as a relative value. Two-dimensional transition metal dichalcogenides have a band gap.

[0058] As shown in Figure 3, in MoS2, the density of states is high in the conduction band and valence band, while the density of states in the band gap is low. When the channel layer 13 has n-type polarity, the Fermi level Efc is located within the conduction band of the channel layer 13 (near the bottom). On the other hand, when the channel layer 13 has p-type polarity, the Fermi level Efc is located within the valence band of the channel layer 13 (near the top).

[0059] The electron density of states of MoS2 is approximately 16 times greater than that of graphene near the lower end of the conduction band. Thus, the electron density of states of MoS2 is much larger than that of graphene. Other two-dimensional transition metal dichalcogenides also have a larger electron density of states than graphene, similar to MoS2. In Figure 3, the electron density of states of MoS2 is greater than that of graphene, but the electron density of states of graphene is greater than that of silicon.

[0060] Using a two-dimensional transition metal dichalcogenide as the channel layer 13 is preferable from the viewpoint of improving the sensitivity of the sensor device 10. From the viewpoint of increasing the sensitivity of the sensor device 10, it is preferable that the channel layer 13 has an atomic layer material film formed by 1 to 20 atomic layers, preferably 1 to 4 atomic layers, and particularly 2 atomic layers. As the number of atomic layers forming the atomic layer material film increases, the density of states of electrons near the Fermi level of the channel layer 13 decreases (see, for example, KC Wang et. al., Journal of Applied Physics, 122, 224302, (2017)), so the sensitivity of the sensor device 10 to the external electric field E decreases.

[0061] Figure 4(A) shows the relationship between energy levels when the channel layer 13 and the dielectric layer 12 are separated. Here, the channel layer 13 is formed from a two-dimensional transition metal dichalcogenide. The left side of Figure 4(A) shows the density of states (DOS) distribution of electrons in the channel layer 13. The right side of Figure 4(A) shows the trap level band and the density of states (DOS) distribution of the trap level band in the dielectric layer 12. This also applies to Figure 4(B). The channel layer 13 has n-type polarity, and the Fermi level Efc is located at the lower end of the conduction band of the channel layer 13.

[0062] At the interface between the dielectric layer 12 and the channel layer 13, there is a trap level band containing multiple trap levels. The trap level band is located near the center of the band gap of the dielectric layer 12.

[0063] Figure 4(B) shows the relationship between energy levels when the channel layer 13 and the dielectric layer 12 are in contact. Figure 4(B) represents the state in the sensor device 10 shown in Figure 1(A). Figure 4(B) shows the state before electrons in the channel layer 13 move to the trap level band of the dielectric layer 12. The Fermi level Efc is located at the lower end of the conduction band of the channel layer 13, as before contact.

[0064] The Fermi level Efc of the channel layer 13 is located above the trap level band at the interface between the dielectric layer 12 and the channel layer 13. When an external electric field E is applied to the sensor device 10, electron movement becomes possible between the energy levels below the Fermi level Efc in the channel layer 13 and the trap level band of the channel layer 13.

[0065] In the sensor device 10, the density of states of electrons near the Fermi level Efc in the channel layer 13 is large (see Figure 3). That is, since there are many electrons in the conduction band below the Fermi level Efc in the channel layer 13, many electrons can move between the channel layer 13 and the trap level band of the dielectric layer 12.

[0066] Figure 4(B) describes the case where the channel layer 13 is an n-type two-dimensional transition metal dichalcogenide, but this description can also be appropriately applied to the case where the channel layer 13 is a p-type two-dimensional transition metal dichalcogenide. In either polarity, it is preferable that the Fermi level of the channel layer 13 is located within the conduction band or valence band of the channel layer 13, and that the Fermi level of the channel layer 13 is located above the trap level band at the interface between the dielectric layer 12 and the channel layer 13. As described above, the present invention is also applicable when the channel layer is an atomic layer material film of one or more atomic layers formed from a two-dimensional transition metal dichalcogenide.

[0067] Next, an example of performing current processing on the dielectric layer 12 of the sensor device 10 will be described below with reference to Figure 5. Figure 5 is a diagram illustrating the current processing of the sensor device 10.

[0068] First, a dielectric layer 12 is formed on the substrate 11 so that its second surface 12B is exposed, and a channel layer 13 is formed on the second surface 12B of the dielectric layer 12. A source electrode 14 and a drain electrode 15 are formed on the channel layer 13 so that they are spaced apart and facing each other, thereby forming a laminate 200.

[0069] Next, the first surface 11A of the substrate 11 of the laminate 200 and the current source 20 are electrically connected via wiring 22, and the source electrode 14 and drain electrode 15 are electrically connected to the current source 20 via wiring 21. By using a substrate 11 to which impurities have been added, the current source 20 and the substrate 11 can be connected by wiring 22 without placing electrodes on the substrate 11.

[0070] Next, power is supplied from the current source 20 to the laminate 200, causing a current to flow through the second surface 12B of the dielectric layer 12 at a predetermined current density for a predetermined time. The current density is obtained by dividing the current flowing from the current source 20 by the area of ​​the second surface 12B when viewed from above. The current from the current source 20 flows through the dielectric layer 12 as a tunnel current.

[0071] When an electric current passes through the second surface 12B of the dielectric layer 12, the interatomic bonds of the atoms forming the dielectric layer 12 are broken, and vacancies can be formed on the second surface 12B. Furthermore, atoms whose interatomic bonds have been broken can become interstitial atoms on the second surface 12B of the dielectric layer 12. These vacancies and interstitial atoms form carrier trap levels on the second surface 12B, so the number of trap levels on the second surface 12B increases.

[0072] Next, it will be explained that when an external electric field E is applied to the sensor device 10, the electric field strength is measured as a change in drain current.

[0073] In Figure 1(A), a positive external electric field E is applied to the sensor device 10 from an external source. The electric field lines of the positive external electric field E extend from the channel layer 13 toward the substrate 11. The electric field lines of the external electric field E enter the sensor device 10 from the input / output region 10a and exit to the outside from the first surface 11A of the substrate 11.

[0074] Due to the external electric field E passing through the input / output region 10a of the sensor device 10, electrons in the trap level band of the second surface 12B of the dielectric layer 12 move to the conduction band of the channel layer 13 as a tunnel current.

[0075] The number of electrons that move from the trap level band at the interface of the dielectric layer 12 to the conduction band of the channel layer 13 depends on the magnitude of the external electric field E. Furthermore, the number of electrons that move to the conduction band of the channel layer 13 depends on the trap level density of the trap levels on the second surface 12B of the dielectric layer 12. Furthermore, the number of electrons that move to the conduction band of the channel layer 13 depends on the density of states of electrons near the Fermi level of the channel layer 13. Furthermore, the number of electrons that move to the conduction band of the channel layer 13 depends on the area of ​​the input / output region 10a.

[0076] As the number of electrons in the channel layer 13 increases, the magnitude of the drain current flowing through the channel region 131 between the source electrode 14 and the drain electrode 15 changes.

[0077] The sensor device 10 can measure the magnitude of the external electric field E based on the magnitude of the change in the drain current value, with the drain current value when no external electric field E is applied to the sensor device 10 as a reference.

[0078] Figure 6 shows the state in which a negative external electric field E is applied to the sensor device 10. The electric field lines of the negative external electric field E extend in the direction from the substrate 11 toward the channel layer 13. The electric field lines of the external electric field E enter the sensor device 10 from the first surface 11A of the substrate 11 and exit to the outside from the input / output region 10a.

[0079] An external electric field E passing through the first surface 11A of the substrate 11 in the sensor device 10 causes holes in the trap level band of the second surface 12B of the dielectric layer 12 to move as tunnel currents to the conduction band of the channel layer 13. The difference between the energy level of the conduction band and the energy level of the trap level band can disappear through inelastic scattering processes such as lattice vibrations. In the channel layer 13, the number of holes increases as holes move to the conduction band of the channel layer 13.

[0080] As the number of holes in the channel layer 13 increases, the magnitude of the drain current flowing through the channel region 131 between the source electrode 14 and the drain electrode 15 changes.

[0081] The sensor device 10 can measure the magnitude of the external electric field E based on the magnitude of the change in the drain current value, with the drain current value when no external electric field E is applied to the sensor device 10 as a reference.

[0082] Figure 7 shows the relationship between the drain current and gate voltage of the sensor device 10. The sensor device 10 in this embodiment can operate as an ambipolar transistor.

[0083] A gate voltage is applied to the first surface 11A of the substrate 11, and a drain voltage V is applied between the source electrode 14 and the drain electrode 15. D The drain current flowing between the source electrode 14 and the drain electrode 15 was measured when the gate voltage was varied by applying a voltage. Note that in an ambipolar transistor, drain current flows even when the gate voltage is zero.

[0084] Figure 7 shows the measurement results of the sensor device 10 after current treatment of the dielectric layer 12 for 2 minutes and 3 minutes. The sensor device 10 used had a substrate 11 made of a silicon substrate, a dielectric layer 12 made of silicon dioxide, and a channel layer 13 made of graphene. The thickness of the dielectric layer 12 was 90 nm. The channel layer 13 was formed using the CVD method. The channel region 131 had a width of 50 μm and a length of 30 μm.

[0085] As shown in Figure 5, current treatment was performed on the dielectric layer 12. The current treatment was 2.65 × 10⁻⁶ -4 A / cm 2 The measurements were performed at the specified current density for 2 minutes and 3 minutes. Figure 7 shows the measurement results for the case where no current treatment was applied to the dielectric layer 12 (0 minutes).

[0086] As shown in Figure 7, nearly identical drain current and gate voltage relationships were obtained for the sensor device 10 that underwent current processing for 2 minutes and 3 minutes, and for the sensor device that did not undergo current processing.

[0087] The carrier mobility μ was determined from the measurement results shown in Figure 7. As shown in Figure 7, the carrier mobility μ was approximately the same regardless of the current processing time for the dielectric layer 12. From this, it can be concluded that there is no change in the carrier density of the channel layer 13 due to the current processing.

[0088] Figure 8 illustrates the measurement of an external electric field using the sensor device 10. Next, the measurement of the external electric field E using the sensor device 10 will be explained below with reference to Figure 8.

[0089] The sensor device 10 was positioned between a pair of electrically conductive plates 30 and 31, separated by a 5 cm gap. The sensor device 10 was positioned such that the second surface 13B of the channel layer 13 faced plate 30, and the first surface 11A of the substrate 11 faced plate 31.

[0090] A voltage was applied to the pair of plates 30 and 31 from a voltage source 32. A constant voltage was also applied between the source electrode 14 and the drain electrode 15 from a voltage source 33. The change in the drain current of the sensor device 10 in response to the external electric field E was measured by varying the voltage applied to the pair of plates 30 and 31 from the voltage source 32. The sensor device 10 used for the measurement was the one shown in Figure 7.

[0091] Figure 9 shows the relationship between the responsiveness of the sensor device and the electric field strength of the external electric field. The responsiveness of the sensor device 10 was measured by applying an external electric field E in the range of -1000 to 1000 V / m. The responsiveness of the sensor device 10 is shown as the rate of change of the drain current value relative to the drain current value when the external electric field E is not applied to the sensor device 10. Responsiveness is an example of the sensitivity of the sensor device 10. A negative electric field strength indicates that an electric field strength in the negative direction is applied to the sensor device 10, and a positive electric field strength indicates that an electric field strength in the positive direction is applied to the sensor device 10.

[0092] As shown in Figure 9, the responsiveness of the sensor device 10 that underwent current processing for 2 minutes was higher than that of the sensor device 10 that underwent no current processing (0 minutes). The responsiveness of the sensor device 10 that underwent current processing for 3 minutes was also higher than that of the sensor device 10 that underwent current processing for 2 minutes.

[0093] As shown in Figure 9, the responsiveness of the sensor device 10 subjected to 2 minutes of current processing increased by approximately 0.1% compared to the one not subjected to current processing, and the responsiveness of the sensor device 10 subjected to 3 minutes of current processing increased by approximately 0.2% compared to the one not subjected to current processing.

[0094] Figure 10 shows the relationship between the response of the sensor device 10 and the current processing time. The relationship shown in Figure 10 was created based on the measurement results shown in Figure 9 when the electric field strength was 1000 V / m.

[0095] As shown in Figure 10, the responsiveness of the sensor device 10 after 2 minutes of current processing was approximately twice that of the sensor device without current processing (0 minutes). The responsiveness of the sensor device 10 after 3 minutes of current processing was approximately 3.5 times that of the sensor device without current processing (0 minutes).

[0096] The sensitivity of the sensor device 10 is proportional to the product of carrier mobility and carrier density. From the results shown in Figure 7, it is considered that there is no change in carrier mobility due to current processing.

[0097] Therefore, it is estimated that the carrier density of the channel layer 13 of the sensor device 10 after 2 minutes of current processing will be approximately twice that of the sensor device 10 after no current processing (0 minutes). Furthermore, it is estimated that the carrier density of the channel layer 13 of the sensor device 10 after 3 minutes of current processing will be approximately 3.5 times that of the sensor device 10 after no current processing (0 minutes).

[0098] In FIG. 9, the responsiveness of the sensor device 10 that has undergone current treatment for 2 minutes increased by approximately 0.1% compared to that which has not undergone current treatment (0 minutes). Further, the responsiveness of the sensor device 10 that has undergone current treatment for 3 minutes increased by approximately 0.2% compared to that which has not undergone current treatment (0 minutes).

[0099] The trap level density of a general silicon dioxide film is on the order of 1 to 2×10 10 eV ―1 cm ―2 (see, for example, D. Schroder, “Semiconductor material and device characterization”, 3rd edtion, Willey Interscience, 2006). Referring to this value, it is estimated that the trap level density increased by on the order of 1×10 8 eV ―1 cm ―2 due to the current treatment for 2 minutes. Further, it is estimated that the trap level density increased by on the order of 2×10 8 eV ―1 cm ―2 due to the current treatment for 3 minutes.

[0100] Based on these numerical values, it is considered preferable that the trap level density of carriers on the second surface 12B of the dielectric layer 12 increases within the range of from 10 11 to 10 13 eV ―1 cm ―2 by current treatment or irradiation treatment. The reason for such an estimated range is that the interface trap density of an ideal thermal oxide film is smaller than 10 11 eV -1 cm- 2 , and the defect density that can be controlled and increased by various techniques described in this specification is approximately two orders of magnitude higher than 10 11 eV -1 cm- 2 and is 10 13 eV -1 cm -2This is because it is a realistic upper limit. Also, if the number of carriers moving between the channel layer 13 is increased by about 100 times, a sufficient improvement in sensor sensitivity can be expected.

[0101] Also, based on the above-described numerical values, the trap level density of carriers in the range of 100 nm in the depth direction from the second surface 12B to the first surface 12A of the dielectric layer 12 by current treatment or irradiation treatment is 10 11 ~10 13 eV ―1 cm ―3 It is preferable to increase within the range of. The reason for such a range being estimated is that the interface trap density of an ideal thermal oxide film is 10 11 eV -1 cm -2 is smaller than, and the defect density that can be controlled and increased by various techniques described in this specification is 10 11 eV -1 cm- 2 about two digits higher than 10 13 eV -1 cm -2 This is because it is a realistic upper limit. Also, if the number of carriers moving between the channel layer 13 is increased by about 100 times, a sufficient improvement in sensor sensitivity can be expected.

[0102] Although not disclosed in this specification, it has been confirmed that when the time of current treatment is further increased, the responsiveness of the sensor device 10 further increases, and the rate of increase in responsiveness with respect to the time of subsequent current treatment becomes lower.

[0103] According to the sensor device of the above-described embodiment, since it has a dielectric layer in which more carriers move between the channel layer, an external electric field can be measured with high sensitivity.

[0104] Next, the second and third embodiments of the above-described sensor device will be described below with reference to FIGS. 11 and 12. For points not particularly described for the second and third embodiments, the descriptions detailed for the above-described first embodiment are appropriately applied. Also, the same reference numerals are assigned to the same components.

[0105] Figure 11 shows a second embodiment of the sensor device 110 disclosed herein. The sensor device 110 of this embodiment includes a substrate 11, a dielectric layer 12, a first atomic layer material film 16, a channel layer 13, a second atomic layer material film 17, a source electrode 14, and a drain electrode 15.

[0106] The sensor device 110 differs from the first embodiment described above in that a first atomic layer material film 16 is placed between the dielectric layer 12 and the channel layer 13, and a second atomic layer material film 17 is placed on the channel layer 13.

[0107] The first atomic layer material film 16 has electrical insulating properties and is disposed on the dielectric layer 12. The channel layer 13 is disposed on the first atomic layer material film 16.

[0108] The first atomic layer material film 16 is preferably formed from a material capable of forming a single atomic layer. The first atomic layer material film 16 is formed from one or more atomic layers formed from this material. Examples of this material include hexagonal boron nitride, hexagonal molybdenum disulfide, or hexagonal tungsten disulfide.

[0109] The first atomic layer material film 16 preferably has a lattice mismatch of 10% or less, and more preferably 5% or less, with respect to the graphene forming the channel layer 13. The lattice mismatch is the quotient obtained by dividing the absolute difference between the lattice constant of the first atomic layer material film 16 and the lattice constant of graphene, when the first atomic layer material film 16 is placed on the channel layer 13 such that the degree of agreement between the lattice constant of the first atomic layer material film 16 and the lattice constant of graphene is maximized, by the lattice constant of graphene, and expressing this quotient as a percentage.

[0110] The surface of the dielectric layer 12, formed from silicon dioxide or the like, is usually not flat but has irregularities. Furthermore, impurities may be present on the surface of the dielectric layer 12. When the channel layer 13 is directly placed on the surface of the dielectric layer 12, the state of the surface of the dielectric layer 12 affects the two-dimensional periodic structure of the graphene or two-dimensional transition metal dichalcogenide forming the channel layer 13, causing distortion and electrical influence from impurities. As a result, carriers moving within the channel layer 13 are scattered by the distortion or impurities, which may reduce the carrier mobility. Therefore, in this embodiment, a first atomic layer material film 16 is placed on the surface of the dielectric layer 12, and the channel layer 13 is placed on this first atomic layer material film 16, thereby suppressing the reduction in carrier mobility in the channel layer 13 due to the influence of the dielectric layer 12.

[0111] Here, since the first atomic layer material film 16 has a small degree of lattice mismatch with the material forming the channel layer 13, even if the channel layer 13 is directly placed on the first atomic layer material film 16, distortion in the two-dimensional periodic structure of the material forming the channel layer 13 is suppressed.

[0112] An external electric field E applied to the sensor device 110 causes carriers in the channel layer 13 to tunnel through the first atomic layer material film 16 as a tunnel current and move to the dielectric layer 12. Therefore, it is preferable that the thickness of the first atomic layer material film 16 is thin.

[0113] The thickness of the first atomic layer material film 16 is preferably in the range of 1 to 120 atomic layers. By having a thickness of 1 atomic layer or more of the first atomic layer material film 16, the influence of the dielectric layer 12 on the carrier mobility in graphene can be suppressed.

[0114] The thicker the first atomic layer material film 16, the smaller the change in the drain current flowing between the source electrode 14 and the drain electrode 15 when an external electric field E is applied to the sensor device 110. The thickness of the first atomic layer material film 16 is preferably determined according to the range of the external electric field E to be measured. If the thickness of the first atomic layer material film 16 is too thick relative to the magnitude of the external electric field E, it may not be possible to accurately measure small external electric fields E. A thickness of up to 120 atomic layers of the first atomic layer material film 16 allows for the measurement of the electric field strength of a typical thundercloud. Furthermore, from the viewpoint of accurately measuring the external electric field strength due to a thundercloud, a thickness of 1 to 40 atomic layers of the first atomic layer material film 16 is preferable for obtaining a large change in drain current.

[0115] The second atomic layer material film 17 is electrically insulating and is placed on the channel layer 13. The second atomic layer material film 17 protects the channel layer 13. The portion of the second atomic layer material film 17 that is exposed to the outside acts as an input / output region 110a to which the sensor device 110 inputs or outputs an external electric field E.

[0116] The second atomic layer material film 17 is preferably formed from a material capable of forming a single atomic layer. The second atomic layer material film 17 is formed from one or more atomic layers formed from this material. Examples of this material include hexagonal boron nitride, molybdenum disulfide, or tungsten disulfide. The second atomic layer material film 17 has a lattice mismatch with graphene forming the channel layer 13 that is preferably 10% or less, and particularly preferably 5% or less. The explanation for the first atomic layer material film 16 described above can be appropriately applied to the explanation for the lattice mismatch of the second atomic layer material film 17.

[0117] The second atomic layer material film 17 is directly placed on the channel layer 13. However, if the degree of lattice mismatch between the material forming the second atomic layer material film 17 and the material forming the channel layer 13 is large, distortion occurs in the two-dimensional periodic structure of the material forming the channel layer 13. As a result, carriers moving within the channel layer 13 are scattered, and the carrier mobility decreases. Therefore, in this embodiment, by placing the second atomic layer material film 17, which has a small degree of lattice mismatch with the material forming the channel layer 13, on the channel layer 13, the decrease in carrier mobility in the channel layer 13 due to the influence of the second atomic layer material film 17 is suppressed.

[0118] The thickness of the second atomic layer material film 17 is preferably in the range of 1 to 300 atomic layers, particularly preferably in the range of 1 to 120 atomic layers, and even more preferably in the range of 1 to 40 atomic layers. A thickness of 1 atomic layer or more in the second atomic layer material film 17 provides physical protection for the channel layer 13. Furthermore, if the thickness of the second atomic layer material film 17 is greater than 300 layers, there is a risk that the attenuation of the external electric field E in the second atomic layer material film 17 will increase.

[0119] According to the sensor device of this embodiment described above, since the first atomic layer material film is placed on top of the channel layer, distortion in the two-dimensional periodic structure of the material forming the channel layer 13 is suppressed, thereby improving the responsiveness to an external electric field. Furthermore, according to the sensor device of this embodiment, since the second atomic layer material film is placed on top of the channel layer, the channel layer is protected. In addition, according to the sensor device of this embodiment, the same effects as in the first embodiment can be obtained.

[0120] Figure 12 shows a third embodiment of the sensor device disclosed herein. The sensor device 120 of this embodiment includes a substrate 11, a dielectric layer 12, a channel layer 13, a second dielectric layer 18, a source electrode 14, and a drain electrode 15.

[0121] The sensor device 120 differs from the first embodiment described above in that a second dielectric layer 18 is arranged on the channel layer 13.

[0122] The second dielectric layer 18 protects the channel layer 13. The portion of the second dielectric layer 18 that is exposed to the outside acts as an input / output region 120a into which the sensor device 120 inputs or outputs an external electric field E.

[0123] As the second dielectric layer 18, a dielectric material such as silicon dioxide, aluminum oxide, or silicon nitride can be used from the viewpoint of protecting the channel layer 13.

[0124] Furthermore, by using a material with a high dielectric constant as the second dielectric layer 18, the external electric field can be amplified and acted upon the channel layer 13. Examples of materials capable of amplifying the external electric field include silicon dioxide, silicon nitride, zirconium dioxide, and hafnium dioxide.

[0125] According to the sensor device of this embodiment described above, the channel layer 13 can be protected by the second dielectric layer. Furthermore, according to the sensor device of this embodiment, the measurement sensitivity of the external electric field can be improved by amplifying the external electric field. In addition, according to the sensor device of this embodiment, the same effects as in the first embodiment can be obtained.

[0126] Next, a preferred first embodiment of the method for manufacturing the sensor device disclosed herein, as described above, will be described below with reference to Figures 13 and 14.

[0127] First, as shown in Figure 13(A), a substrate 11 having a first surface 11A and a second surface 11B is prepared. As the substrate 11, for example, a semiconductor substrate such as a silicon substrate, silicon carbide, or compound semiconductor can be used.

[0128] Next, as shown in Figure 13(B), a dielectric layer 12 is formed on the second surface 11B of the substrate 11. When a silicon substrate is used as the substrate 11, it is preferable to form a silicon dioxide layer as the dielectric layer 12. This silicon dioxide layer is formed, for example, by thermal oxidation, CVD, or sputtering. From the viewpoint of increasing the number of trap levels on the second surface 12B of the dielectric layer 12, it is preferable to form the dielectric layer 12 using CVD or sputtering. From the viewpoint of facilitating the manufacture of the dielectric layer 12, it is preferable to form the silicon dioxide layer on the silicon substrate 11 using thermal oxidation. When a silicon dioxide layer is formed as the dielectric layer 12 using thermal oxidation, the interface between the silicon dioxide layer and silicon becomes the second surface 11B of the substrate 11 and the first surface 12A of the dielectric layer 12.

[0129] Next, as shown in Figure 14(A), a channel layer 13 is formed on the dielectric layer 12. The channel layer 13 has a first surface 13A and a second surface 13B. The first surface 13A is located on the dielectric layer 12, and the second surface 13B is exposed to the outside.

[0130] As the channel layer 13, an atomic layer material film is formed consisting of one or more atomic layers of graphene, or one or more atomic layers formed of a two-dimensional transition metal dichalcogenide.

[0131] The graphene channel layer 13 is formed, for example, by a peeling method or a CVD method and transferred onto the dielectric layer 12. The thickness and quality of the channel layer 13 are measured, for example, by Raman spectroscopy. Forming the channel layer 13 using a peeling method is preferable from the viewpoint of obtaining a high-quality channel layer 13 with few defects. From the viewpoint of commercial production of sensor devices, it is preferable to form the channel layer 13 using a CVD method.

[0132] From the viewpoint of obtaining high carrier mobility, it is preferable that the channel layer 13 be formed using 1 to 10 atomic layers of graphene, particularly 1 to 3 atomic layers. In particular, the highest carrier mobility can be obtained by forming the channel layer 13 using a single atomic layer of graphene. Polarity may be imparted to the channel layer 13 by adding impurities to the graphene.

[0133] The channel layer 13 of the two-dimensional transition metal dichalcogenide can be formed, for example, by a peeling method or a CVD method. Forming the channel layer 13 by a peeling method is preferable from the viewpoint of obtaining a high-quality atomic layer material film with few defects. The thickness of the channel layer 13 is preferably in the range of 1 to 20 layers, more preferably 1 to 4 atomic layers. The thickness and quality of the channel layer 13 are measured, for example, by Raman spectroscopy.

[0134] The channel layer 13 can be formed using molybdenum (Mo), tungsten (W), or niobium (Nb) as the transition metal, and sulfur (S), selenium (Se), or tellurium (Te) as the chalcogenide element. For example, MoS2, MoSe2, WS2, WSe2, NbS2, and NbSe2 can be used as the two-dimensional transition metal dichalcogenide.

[0135] Next, as shown in Figure 14(B), the source electrode 14 and the drain electrode 15 are formed on the channel layer 13 so as to face each other with a gap in between, thereby obtaining the laminate 200. The source electrode 14 and the drain electrode 15 can be formed as a laminate of chromium and gold.

[0136] Next, as shown in Figure 5, current processing is performed on the dielectric layer 12 of the laminate 200 to obtain the sensor device 10 of the first embodiment.

[0137] Specifically, the first surface 11A of the substrate 11 in the laminate 200 and the current source 20 are electrically connected via wiring 22, and the source electrode 14 and drain electrode 15 are electrically connected to the current source 20 via wiring 21. By using a substrate 11 to which impurities have been added, the current source 20 and the substrate 11 can be connected by wiring 22 without placing electrodes on the substrate 11. Alternatively, the wiring 22 and the substrate 11 may be connected via electrodes.

[0138] Next, power is supplied from the current source 20 to the laminate 200, causing a current to flow through the second surface 12B of the dielectric layer 12 at a predetermined current density for a predetermined time. The current density is obtained by dividing the current flowing from the current source 20 by the area of ​​the second surface 12B when viewed from above. The current from the current source 20 flows through the dielectric layer 12 as a tunnel current.

[0139] By passing an electric current through the second surface 12B of the dielectric layer 12, vacancies and interstitial atoms are formed on the second surface 12B, thus increasing the number of carrier trap levels on the second surface 12B of the dielectric layer 12.

[0140] In the example shown in Figure 5, the current flows from the substrate 11 to the channel layer 13, but the current may also flow from the channel layer 13 to the substrate 11. The current may also flow through the second surface 12B in the thickness direction. Alternatively, the current may flow in the plane direction of the second surface 12B. From the viewpoint of facilitating current processing, it is preferable to flow the current through the channel layer 13 in the thickness direction.

[0141] When an electric current passes through the second surface 12B of the dielectric layer 12, the interatomic bonds of the atoms forming the dielectric layer 12 are broken, and vacancies can be formed on the second surface 12B. Furthermore, atoms whose interatomic bonds have been broken may migrate to the second surface 12B of the dielectric layer 12 and become interstitial atoms. These vacancies and interstitial atoms form carrier trap levels on the second surface 12B. Note that vacancies and interstitial atoms may be formed throughout the entire thickness of the dielectric layer 12.

[0142] The amount of vacancies and interstitial atoms formed on the second surface 12B of the dielectric layer 12 is determined by the current stress, which is determined by the total charge per unit area flowing on the second surface 12B. Specifically, the current stress is determined by the product of the current density per unit area and the time the current is applied. That is, the increase in the number of carrier trap levels on the second surface 12B is determined by the current stress. Note that interstitial atoms do not need to be formed as long as at least vacancies are formed by the current treatment.

[0143] The magnitude of the current density may be greater than or equal to the magnitude required to break the interatomic bonds of the atoms forming the dielectric layer 12. Alternatively, since it is sufficient that the interatomic bonds of the atoms forming the dielectric layer 12 are broken as a result of applying current stress to the dielectric layer 12, the magnitude of the current density may be less than the magnitude required to break the interatomic bonds of the atoms forming the dielectric layer 12.

[0144] As current stress, the total charge per unit area is 0.265 × 10⁻⁶. -2 C / cm 2 ~10°C / cm 2 Within this range, it is preferable that the current flows through the second surface 12B of the dielectric layer 12. The current stress is particularly 0.395 × 10⁻⁶. -2 C / cm 2 ~10°C / cm 2 Within the range of 1 × 10 -2 C / cm 2 ~10°C / cm 2 It is preferable that it be within the range of [specify range].

[0145] The total charge is preferably set appropriately within the above range, depending on the dielectric breakdown strength or volume resistivity of the dielectric layer 12.

[0146] The total charge per unit area is 0.265 × 10⁻⁶. -2 C / cm 2When a current stress greater than the specified stress is applied to the dielectric layer 12, a sufficient number of carrier trap levels can be formed on the second surface 12B of the dielectric layer 12. On the other hand, the current stress is such that the total charge per unit area is 10 C / cm². 2 If the stress exceeds a certain level, the physical state of the second surface 12B of the dielectric layer 12 may be damaged.

[0147] Furthermore, it is preferable to appropriately set the total charge amount within the range described above, depending on the thickness of the dielectric layer 12. When the dielectric layer 12 is thin, it is preferable to reduce the total charge amount from the viewpoint of not damaging the second surface 12B of the dielectric layer 12. On the other hand, when the dielectric layer 12 is thick, it is preferable to increase the total charge amount from the viewpoint of forming sufficient defect levels.

[0148] Total charge per unit area is 1 × 10⁻⁶ -2 C / cm 2 The resulting current stress is, for example, when the current density is 1 × 10⁻⁶. -5 A / cm 2 The combination of 1 × 10⁻¹⁰ and the time for which the current is applied is 1000 seconds (approximately 17 minutes). -5 A / cm 2 This current density is about two orders of magnitude larger than the tunnel current of a typical MOSFET.

[0149] Furthermore, the total charge per unit area is 1 × 10⁻⁶ -2 C / cm 2 The resulting current stress is, for example, when the current density is 1 × 10⁻⁶. -6 A / cm 2 The combination of this and the time for which the current is applied is given as 10,000 seconds (approximately 170 minutes). 10,000 seconds (approximately 170 minutes) is an acceptable time in commercial production.

[0150] Furthermore, the total charge per unit area is 1 × 10⁻⁶ -2 C / cm 2 The resulting current stress is, for example, when the current density is 1 A / cm². 2The combination of the current flow time and the current flow time of 10 milliseconds is given. 10 milliseconds is a controllable time in commercial production. On the other hand, if the current flow time is shorter than 10 milliseconds, the proportion of time required for preparing for current processing becomes relatively larger, so the advantage of shortening the current flow time to less than 10 milliseconds is lost. The total charge per unit area is 0.265 × 10 -2 C / cm 2 The resulting current stress is, for example, when the current density is 0.265 A / cm². 2 The combination of this and the time for which the current flows is 10 milliseconds is given.

[0151] Furthermore, the total charge per unit area is 10 C / cm². 2 The resulting current stress is, for example, when the current density is 1 A / cm². 2 The combination of the current flow time and the total charge amount per unit area is given as 10 seconds. When a large current stress is applied, the voltage used for current processing also increases. The upper limit of the voltage used for current processing is set according to the dielectric breakdown voltage and volumetric efficiency of the dielectric layer 12, so the current density and time can be appropriately set according to the upper limit of the voltage used for current processing.

[0152] As a result of the current treatment, the carrier trap level density on the second surface 12B of the dielectric layer 12 is 10 11 ~10 13 eV ―1 cm ―2 It is preferable that it increases within the range of 10. From the viewpoint of sufficiently increasing the carrier density of the channel layer 13, 11 eV ―1 cm ―2 It is considered preferable that the trap level density increases above the above limit. Furthermore, from the viewpoint of maintaining the physical state of the second surface 12B of the dielectric layer 12, the upper limit of the increasing trap level density is 10 13 eV ―1 cm ―2 It can be considered to be of a certain degree.

[0153] According to the manufacturing method of the sensor device of this embodiment described above, a sensor device capable of measuring an external electric field with high sensitivity can be obtained.

[0154] In conventional MOSFETs, leakage current can flow through the oxide film near the channel region due to leakage from the channel region during operation. However, the current density of the current processing described above is two to three orders of magnitude larger than such leakage current.

[0155] Next, a modified example of the first embodiment of the method for manufacturing the sensor device described above will be explained below with reference to Figures 15(A) and 15(B).

[0156] In the embodiment described above, the current processing was performed after the source electrode 14 and drain electrode 15 were formed, but the current processing may also be performed after the dielectric layer 12 is formed but before the channel layer 13 is formed.

[0157] In this modified example, as shown in Figure 15(A), after the process shown in Figure 13(B), an electrode layer 19 is formed on the dielectric layer 12 to obtain a laminate 210. For example, gold, copper, or aluminum can be used as the electrode layer 19.

[0158] Next, as shown in Figure 15(B), the first surface 11A of the substrate 11 in the laminate 210 and the current source 20 are electrically connected via wiring 22, and the electrode layer 19 and the current source 20 are electrically connected via wiring 21. By using a substrate 11 to which impurities have been added, the current source 20 and the substrate 11 can be connected by wiring 22 without placing electrodes on the substrate 11.

[0159] Then, after current processing is performed on the dielectric layer 12 of the laminate 210, the steps shown in Figures 14(A) and 14(B) are carried out to obtain the sensor device 10 of the first embodiment. Specifically, in the current processing, power is supplied to the laminate 210 from the current source 20 to cause a current to flow through the second surface 12B of the dielectric layer 12 at a predetermined current density for a predetermined time. The conditions described above are applied as appropriate to the current processing conditions.

[0160] Next, a second embodiment of the method for manufacturing the sensor device described above will be explained below with reference to Figure 16. For aspects of the second embodiment that are not specifically described, the detailed explanation of the first embodiment described above will apply as appropriate. Also, the same reference numerals are used for identical components.

[0161] In the manufacturing method of the sensor device of this embodiment, an irradiation process is used to increase the number of carrier trap levels on the second surface 12B of the dielectric layer 12 by irradiating the second surface 12B with radiation. Using charged particles and ultraviolet light as radiation is preferable from the viewpoint of easily increasing the number of trap levels. However, uncharged particles may also be used as radiation. In addition, electromagnetic waves other than ultraviolet rays, such as X-rays, may be used as radiation.

[0162] In this embodiment, as shown in Figure 16, after the process shown in Figure 13(B), an irradiation treatment is performed on the second surface 12B of the dielectric layer 12 by irradiating it with radiation. When the second surface 12B is irradiated with radiation, vacancies and interstitial atoms are formed on the second surface 12B. Since the vacancies and interstitial atoms form carrier trap levels on the second surface 12B, the number of trap levels on the second surface 12B increases. Note that interstitial atoms do not need to be formed as long as at least vacancies are formed by the irradiation treatment.

[0163] The amount of vacancies and interstitial atoms formed on the second surface 12B of the dielectric layer 12 is determined by the irradiation stress, which is determined by the product of the incident radiation energy, the irradiation dose per unit area, and the irradiation time. In other words, the increase in the number of carrier trap levels on the second surface 12B is determined by the irradiation stress.

[0164] The magnitude of the incident radiation energy may be greater than or equal to the magnitude required to break the interatomic bonds of the atoms forming the dielectric layer 12. Alternatively, since the goal is to break the interatomic bonds of the atoms forming the dielectric layer 12 as a result of the irradiation stimulus applied to the dielectric layer 12, the magnitude of the incident radiation energy may be less than the magnitude required to break the interatomic bonds of the atoms forming the dielectric layer 12.

[0165] When radiation is irradiated onto the second surface 12B of the dielectric layer 12, the interatomic bonds of the atoms forming the dielectric layer 12 are broken, and vacancies can be formed on the second surface 12B. Furthermore, atoms or charged particles whose interatomic bonds have been broken can become interstitial atoms on the second surface 12B of the dielectric layer 12. These vacancies and interstitial atoms form carrier trap levels on the second surface 12B, thus increasing the number of trap levels on the second surface 12B.

[0166] Electrons can be used as charged particles. When electrons are used as charged particles, the incident energy is in the range of 0.1 to 500 keV and the total irradiation dose per unit area is 10 -2 μC / cm 2 ~1 mC / cm 2 It is preferable to use irradiation stress determined by a combination of the following ranges.

[0167] The incident energy is 0.1 keV and the total irradiation dose per unit area is 10 -2 μC / cm 2 By applying a stress greater than the irradiation stress determined by the combination of factors to the dielectric layer 12, a sufficient number of carrier trap levels can be formed on the second surface 12B of the dielectric layer 12. On the other hand, if the irradiation stress is such that the incident energy is 500 keV and the total irradiation dose per unit area is 1 mC / cm², then the irradiation stress is such that the incident energy is 500 keV and the total irradiation dose per unit area is 1 mC / cm². 2 If the stress exceeds the stress determined by the combination of factors, the physical state of the second surface 12B of the dielectric layer 12 may be damaged.

[0168] Furthermore, ions such as gallium ions or helium ions can be used as charged particles. When ions are used as charged particles, the incident energy is in the range of 0.5 keV to 2 MeV and the total irradiation dose per unit area is 1 μC / cm². 2 ~100mC / cm 2 It is preferable to use irradiation stress determined by a combination of the following ranges. Note that the ions mentioned above are just examples, and other ions may be used.

[0169] The incident energy is 0.5 keV and the total irradiation dose per unit area is 1 μC / cm². 2 By applying a stress greater than the irradiation stress determined by the combination of factors to the dielectric layer 12, a sufficient number of carrier trap levels can be formed on the second surface 12B of the dielectric layer 12. On the other hand, if the irradiation stress is such that the incident energy is 2 MeV and the total irradiation dose per unit area is 100 mC / cm² 2 If the stress exceeds the stress determined by the combination of factors, the physical state of the second surface 12B of the dielectric layer 12 may be damaged.

[0170] Ultraviolet light may also be used. When using ultraviolet light, the incident energy should be in the range of 4 to 50 eV, and the irradiation dose per unit area should be 10 10 ~10 12 photons / cm 2 It is preferable to use irradiation stress determined by a combination of the range and the irradiation time, which ranges from 1 second to 1000 seconds.

[0171] The incident energy is 4 eV, and the irradiation dose per unit area is 10 10 photons / cm 2 Furthermore, by applying a stress greater than the irradiation stress determined by the combination of the irradiation time and the dielectric layer 12, a sufficient number of carrier trap levels can be formed on the second surface 12B of the dielectric layer 12. On the other hand, if the irradiation stress is such that the incident energy is 50 eV and the irradiation amount per unit area is 10 12 photons / cm 2Furthermore, if the stress exceeds the stress determined by the combination of irradiation time and 1000 seconds, the physical state of the second surface 12B of the dielectric layer 12 may be damaged.

[0172] As a result of the irradiation treatment, the carrier trap level density on the second surface 12B of the dielectric layer 12 is 10 11 ~10 13 eV ―1 cm ―2 It is preferable that it increases within the range of 10. From the viewpoint of sufficiently increasing the carrier density of the channel layer 13, 11 eV ―1 cm ―2 It is considered preferable that the trap level density increases above the above limit. Furthermore, from the viewpoint of maintaining the physical state of the second surface 12B of the dielectric layer 12, the upper limit of the increasing trap level density is 10 13 eV ―1 cm ―2 It can be considered to be of a certain degree.

[0173] According to the manufacturing method of the sensor device of this embodiment described above, a sensor device capable of measuring an external electric field with high sensitivity can be obtained.

[0174] In the present invention, the sensor device, the method for manufacturing the sensor device, and the measurement method for measuring the external electric field of the above-described embodiment can be modified as appropriate without departing from the spirit of the present invention. Furthermore, the constituent elements of one embodiment can be appropriately applied to other embodiments.

[0175] For example, in the embodiment described above, the sensor device did not have a gate electrode, but the sensor device may have a gate electrode. The gate electrode may be located on the channel layer via a gate insulating film. Alternatively, the gate electrode may be located on the second surface of the substrate via a gate insulating film.

[0176] Furthermore, in the sensor device of the second embodiment described above, the first atomic layer material film was placed on top of the channel layer, but the second atomic layer material film does not necessarily have to be placed on top of the channel layer. [Examples]

[0177] The sensor devices disclosed herein will be further described below with reference to examples. However, the scope of the present invention is not limited to these examples.

[0178] (Example 1) As shown in Figure 5, a dielectric layer 12 was formed on the substrate 11 with its second surface 12B exposed, a channel layer 13 was formed on the second surface 12B of the dielectric layer 12, and a source electrode 14 and a drain electrode 15 were formed on the channel layer 13 with a gap between them to face each other, thereby forming a laminate 200. A silicon substrate was used as the substrate 11, silicon dioxide was used as the dielectric layer 12, and graphene was used as the channel layer 13. The channel layer 13 was formed using the CVD method. The channel region 131 had a width of 50 μm and a length of 30 μm.

[0179] Next, the first surface 11A of the substrate 11 of the laminate 200 and the current source 20 are electrically connected via wiring 22, and the source electrode 14 and drain electrode 15 are electrically connected to the current source 20 via wiring 21. Current flows from the substrate 11 towards the channel layer 13.

[0180] Next, power is supplied from the current source 20 to the laminate 200, and the current passing through the second surface 12B of the dielectric layer 12 is 2.65 × 10⁻¹⁰ -4 A / cm 2 By applying the current density for 15 seconds, the sensor device of Example 1 was obtained. The dielectric layer 12 has a total charge amount of 0.3975 × 10⁻¹⁶ per unit area. -2 C / cm 2 Then, current was passed through the second surface 12B.

[0181] (Example 2) The current source 20 supplies power to the laminate 200, and the current passing through the second surface 12B of the dielectric layer 12 is 2.65 × 10⁻¹⁰. -4 A / cm 2The sensor device of Example 2 was obtained in the same manner as in Example 1, except that the current density was applied for 30 seconds. The dielectric layer 12 has a total charge amount of 0.795 × 10⁻¹⁶ per unit area. -2 C / cm 2 Then, current was passed through the second surface 12B.

[0182] (Comparative Example 1) A sensor device of Comparative Example 1 was obtained in the same manner as in Embodiment 1, except that no current processing was performed on the laminate 200.

[0183] Figure 17 shows the relationship between the responsiveness of the sensor devices in Examples 1 and 2 and Comparative Example 1 and the electric field strength of the external electric field.

[0184] The responsiveness of the sensor devices of Examples 1 and 2 and Comparative Example 1 was measured by applying an external electric field E in the range of 0 to 1000 V / m. The responsiveness of the sensor device 10 is expressed as the absolute value of the rate of change of the drain current value, with the drain current value when no external electric field E is applied to the sensor device 10 as the reference. A positive electric field strength indicates that an electric field strength in the positive direction is applied to the sensor device 10.

[0185] In the responsiveness measurements of the sensor devices in Examples 1 and 2 and Comparative Example 1, compared to the measurement shown in Figure 9, the leakage current during current processing was suppressed, and charge was efficiently injected into the dielectric layer 12. Furthermore, in the responsiveness measurements of the sensor devices in Examples 1 and 2 and Comparative Example 1, compared to the measurement shown in Figure 9, unintended changes in the electric field shape were suppressed, and the external electric field E was brought closer to the ideal electric field between parallel plates.

[0186] As shown in Figure 17, the responsiveness of Example 1 (current processing time: 15 seconds) was higher than that of Comparative Example 1 (current processing time: 0 seconds). The responsiveness of Example 2 (current processing time: 30 seconds) was also higher than that of Example 1 (current processing time: 15 seconds).

[0187] As shown in Figure 17, when the electric field strength was 1000 V / m, the response of Example 1 (current processing time: 15 seconds) was approximately 0.48% higher than that of Comparative Example 1 (current processing time: 0 seconds), and the response of Example 2 (current processing time: 30 seconds) was approximately 1.14% higher than that of Comparative Example 1 (current processing time: 0 seconds).

[0188] Based on the measurement results of Example 1 (current processing time: 15 seconds) and Example 2 (current processing time: 30 seconds), the relationship between current processing time and responsiveness at an electric field strength of 1000 V / m was obtained. Based on the relationship between current processing time and responsiveness at an electric field strength of 1000 V / m, it was found that the responsiveness when the current processing time was 10 seconds increased by approximately 20% compared to Comparative Example 1. The total charge in this case is 0.265 × 10⁻⁶. -2 / cm 2 This is the result. [Explanation of Symbols]

[0189] 10, 110, 120 Sensor Devices 10a, 110a, 120a input / output area 11 circuit boards 11A 1st page 11B 2nd side 12 Dielectric layer 12A 1st page 12B 2nd side 13 channel layers 13A 1st page 13B 2nd side 131 Channel Area 14. Source electrode (first electrode) 15. Drain electrode (second electrode) 16 First atomic layer material film 17 Second atomic layer material film 18. Second dielectric layer

Claims

1. A sensor device capable of measuring the electric field strength of an external electric field, A dielectric layer having a first surface and a second surface, A channel layer having a channel region is disposed on the second surface of the dielectric layer, A first electrode and a second electrode are arranged on the channel layer so as to face each other across the channel region, Equipped with, A sensor device characterized in that the dielectric layer is manufactured such that vacancies are formed on the second surface by passing an electric current through the second surface, or by irradiating the second surface with radiation, thereby increasing the number of carrier trap levels on the second surface.

2. By passing an electric current through the second surface, vacancies are formed on the second surface, or by irradiating the second surface with radiation, the carrier trap level density on the second surface is 10 １１ ~10 １３ eV ―１ cm ―２ The sensor device according to claim 1, which is increasing within the range.

3. By passing an electric current through the second surface, vacancies are formed on the second surface, or by irradiating the second surface with radiation, the carrier trap level density in the 100 nm depth range from the second surface to the first surface of the dielectric layer is 10 １１ ~10 １３ eV ―１ cm ―３ The sensor device according to claim 1, which is increasing within the range.

4. The dielectric layer has a total charge amount per unit area of 0.265×10 －２ C / cm ２ to 10 C / cm ２ and a current is passed through the second surface so that holes are formed in the second surface, the sensor device according to claim 1.

5. The dielectric layer is irradiated with respect to the second surface when the incident energy is in the range of 0.1 to 500 keV and the total irradiation amount per unit area is 10 －２ μC / cm ２ ~1 mC / cm ２ Under conditions determined by a combination of the following ranges, electrons are irradiated to form a vacancy on the second surface, or the incident energy is in the range of 0.5 keV to 2 MeV and the total irradiation dose per unit area is 1 μC / cm². ２ ~100 mC / cm ２ Ions are irradiated under conditions determined by a combination of the following ranges to form voids on the second surface, or the incident energy is in the range of 4 to 50 eV, and the irradiation dose per unit area is 10 １０ ~10 １２ photons / cm ２ The sensor device according to claim 1, wherein ultraviolet light is irradiated under conditions determined by a combination of the range and irradiation time in the range of 1 to 1000 seconds to form a void on the second surface.

6. The sensor device according to claim 1, wherein the channel layer has one or more atomic layers of graphene, or one or more atomic layer material films formed of a two-dimensional transition metal dichalcogenide.

7. The sensor device according to any one of claims 1 to 6, wherein the dielectric layer has a thickness in the range of 90 to 300 nm.

8. A method for manufacturing a sensor device capable of measuring the electric field strength of an external electric field, A first step is to form a dielectric layer having a first surface and a second surface on a substrate such that the second surface is exposed. A second step of forming a channel layer on the second surface of the dielectric layer, A third step involves forming the first electrode and the second electrode on the channel layer so that they are separated and facing each other, A fourth step of increasing the number of carrier trap levels on the second surface by passing an electric current through the second surface of the dielectric layer to form vacancies on the second surface, or by irradiating the second surface with radiation to form vacancies on the second surface, It has, A method for manufacturing a sensor device, characterized in that the fourth step is performed between the first step and the second step, or the formation of a void on the second surface of the dielectric layer by passing an electric current through the second surface in the fourth step is performed after the third step.

9. In the fourth step, the total charge per unit area is 0.265 × 10 －２ C / cm ２ ~10°C / cm ２ A method for manufacturing a sensor device according to claim 8, wherein a current is passed through the second surface of the dielectric layer within the range of [specified range].

10. In the fourth step, the second surface of the dielectric layer is exposed to an incident energy in the range of 0.1 to 500 keV and a total irradiation amount per unit area of ​​10 －２ μC / cm ２ ~1 mC / cm ２ The electrons are irradiated under conditions determined by a combination of the following ranges, or the incident energy is in the range of 0.5 keV to 2 MeV and the total irradiation dose per unit area is 1 μC / cm². ２ ~100 mC / cm ２ Ions are irradiated under conditions determined by a combination of the following ranges, or the incident energy is in the range of 4 to 50 eV, and the irradiation dose per unit area is 10 １０ ~10 １２ photons / cm ２ A method for manufacturing a sensor device according to claim 8, wherein ultraviolet light is irradiated under conditions determined by a combination of the range and irradiation time in the range of 1 to 1000 seconds.

11. In the fourth step, the carrier trap level density on the second surface is 10 １１ ~10 １３ eV ―１ cm ―２ A method for manufacturing a sensor device according to claim 8, which increases within the range.

12. In the fourth step, the carrier trap level density in the 100 nm depth range from the second surface to the first surface of the dielectric layer is 10 １１ ~10 １３ eV ―１ cm ―３ A method for manufacturing a sensor device according to any one of claims 8 to 11, wherein the range increases.

13. A measurement method for measuring an external electric field using the sensor device described in claim 1, With an external electric field applied to the sensor device, the current value flowing between the first electrode and the second electrode is measured. Based on the aforementioned current value, the electric field strength of the external electric field is determined. A measurement method characterized by having the following:

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