A micro multi-ion sensing system based on non-gate array and a preparation method thereof

Abstract

The application discloses a kind of micro multi-ion sensing system based on non-gate array and preparation method thereof, belong to electrochemical sensing technical field, including multi-ion sensitive unit and molybdenum disulfide non-gate array;Multi-ion sensitive unit includes metal electrode array, ion sensitive film array and liquid pool, and a plurality of ions are detected simultaneously by ion sensitive film array, and are converted into electric signal and are transmitted to molybdenum disulfide non-gate array by metal electrode array;Molybdenum disulfide non-gate array includes a plurality of molybdenum disulfide non-gate, and molybdenum disulfide non-gate includes metal electrode layer, molybdenum disulfide layer, non-gate input end and non-gate output end, forms two field effect transistors, to amplify received electric signal, and break through Nernst limit by non-gate structure, accurately detect the slight change of ion concentration, with higher sensitivity;By molybdenum disulfide as the channel material of non-gate, the size and power consumption of non-gate are effectively reduced, the integration of system is improved, and the service life of system is prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochemical sensing, and particularly relates to a micro multi-ion sensing system based on a NAND gate array and a preparation method thereof. BACKGROUND

[0002] Ion concentration in human body fluid is closely related to human health. Abnormal ion concentration in human body, i.e. electrolyte disorder, is a common health problem in modern society, which can cause symptoms such as fatigue, dizziness, headache, and even serious diseases such as hypertension, kidney failure, heart failure, etc. Therefore, real-time monitoring of ion concentration in human body is helpful for early prevention and treatment of electrolyte disorder, which can effectively improve people's quality of life. However, current ion concentration detection technology mainly relies on blood tests in hospitals, which cannot meet the needs of portable and real-time health monitoring.

[0003] With the development of microelectronic technology, an ion detection method based on field effect transistor (FET) has been proposed. The basic principle is to cover a layer of ion-sensitive film with strong specificity on the surface of the transistor gate, and to drop the test liquid on the surface of the gate. When the concentration of the corresponding ion in the test liquid changes, the membrane surface potential (i.e. the equivalent potential of the gate) will change, thereby causing the source-drain current to change. By testing the transfer characteristic curve of the transistor, the concentration of the ion to be tested can be calculated. This detection structure has the advantages of simple principle, low cost, fast response, small size, etc., and the processing technology is compatible with the current mature CMOS technology, which has the potential for array preparation.

[0004] However, the sensitivity of this detection method is limited by the Nernst Limit. Taking hydrogen ions as an example, the membrane surface potential changes at most 59.2mV when the hydrogen ion concentration in the test liquid changes by one order of magnitude at room temperature. In actual detection, the ion concentration in the human body is generally in a relatively stable range. In the case of low sensitivity, small concentration fluctuations may be difficult to detect. At the same time, the transfer characteristic curve of the test transistor needs to measure the source-drain current, and the source-drain current of the field effect transistor is related to the type of channel material. Traditional field effect transistors use silicon as the channel, which has a small resistance, resulting in a large source-drain current and high power consumption of the device; new type of field effect transistors represented by two-dimensional materials have a large resistance and strong gate control ability, but the small source-drain current puts higher requirements on the subsequent processing circuit, making it difficult to realize the miniaturization of the ion detection system as a whole. SUMMARY

[0005] In view of one or more of the above defects or improvement needs of the prior art, the present application provides a micro multi-ion sensing system based on a NAND gate array and a preparation method thereof, which can simultaneously detect multiple ion concentrations, has higher sensitivity, and can meet the miniaturization needs of the sensing system.

[0006] To achieve the above object, one aspect of the present application provides a micro multi-ion sensing system based on a non-gate array and a preparation method thereof, which comprises a multi-ion sensitive unit and a molybdenum disulfide non-gate array.

[0007] The multi-ion sensitive unit comprises a metal electrode array, an ion sensitive film array and a liquid pool; the liquid pool is arranged on the first substrate and used for storing a solution to be tested; the metal electrode array is arranged on the first substrate and arranged in the liquid pool and comprises a plurality of first metal electrodes; the ion sensitive film array comprises a plurality of ion sensitive films arranged separately on the first metal electrodes, and different ion sensitive films contain different ion carriers.

[0008] The molybdenum disulfide non-gate array comprises a plurality of molybdenum disulfide non-gates arranged on a second substrate.

[0009] The molybdenum disulfide non-gate comprises a metal electrode layer, a molybdenum disulfide layer, a non-gate input end and a non-gate output end; the non-gate output end, the molybdenum disulfide layer and the metal electrode layer are arranged on the second substrate, the molybdenum disulfide layer comprises a first molybdenum disulfide layer and a second molybdenum disulfide layer; the metal electrode layer comprises a second metal electrode and a third metal electrode arranged separately on both sides of the non-gate output end, the second metal electrode and the non-gate output end are connected to both ends of the first molybdenum disulfide layer, and the third metal electrode and the non-gate output end are connected to both ends of the second molybdenum disulfide layer; a first insulating layer is arranged on one side of the non-gate output end, the first molybdenum disulfide layer and the second metal electrode, and the non-gate input end is arranged on the first insulating layer; a second insulating layer is arranged on the other side of the non-gate output end, the second molybdenum disulfide layer and the third metal electrode, and one end of the non-gate output end extending away from the second substrate is arranged on the second insulating layer.

[0010] Each first metal electrode in the metal electrode array is connected to each non-gate input end in the molybdenum disulfide non-gate array in one-to-one correspondence.

[0011] As a further improvement of the present application, the molybdenum disulfide layer is a single-atom monocrystalline structure with a thickness of 0.5-1 nm.

[0012] As a further improvement of the present application, the first insulating layer and the second insulating layer are made of any one of aluminum oxide, hafnium oxide and silicon dioxide and have a thickness of 30-50 nm.

[0013] As a further improvement of the present application, the non-gate input end, the non-gate output end and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower layer metal is any one of Ti and Cr, and the thickness is 5-10 nm; the material of the upper layer metal is any one of Au, Ag, Cu, Pd and Pt, and the thickness is 20-30 nm.

[0014] As a further improvement of the present application, when the ion to be measured is hydrogen ion, the corresponding first metal electrode has a material of TiN and a thickness of 20-100 nm, and no ion-sensitive film is arranged on the first metal electrode; when the ion to be measured is other ion, the corresponding first metal electrode is a double-layer metal stack structure, wherein the lower layer metal is any one of Ti and Cr, and the thickness is 5-10 nm; the upper layer metal is Au, and the thickness is 20-30 nm.

[0015] As a further improvement of the present application, the first substrate and the second substrate are both SiO2 / Si substrates, and the thickness of SiO2 in the SiO2 / Si substrate is 200-300 nm.

[0016] As a further improvement of the present application, the material of the liquid storage pool is any one of polydimethylsiloxane and polymethyl methacrylate.

[0017] In another aspect of the present application, a preparation method of a multi-ion sensitive unit is provided, which is used for preparing the multi-ion sensitive unit in the above-mentioned micro multi-ion sensing system based on a non-gate array, and comprises the following steps:

[0018] (1) coating photoresist on the surface of the first substrate, and patterning the photoresist;

[0019] (2) growing metal on the surface of the photoresist by using sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array;

[0020] (3) dropping each ion carrier and its corresponding sensitive solution on the surface of its corresponding first metal electrode respectively and drying to obtain an ion-sensitive film array;

[0021] (4) bonding the liquid storage pool on the first substrate to complete the preparation of the multi-ion sensitive unit.

[0022] In another aspect of the present application, a preparation method of a molybdenum disulfide non-gate array is provided, which is used for preparing the molybdenum disulfide non-gate array in the above-mentioned micro multi-ion sensing system based on a non-gate array, and comprises the following steps:

[0023] (1) growing a single-layer molybdenum disulfide on the surface of the second substrate by using chemical vapor deposition method;

[0024] (2) coating photoresist on the surface of the single-layer molybdenum disulfide, and patterning the photoresist;

[0025] (3) etching the molybdenum disulfide, and removing the photoresist on the surface of the single-layer molybdenum disulfide after etching to obtain a molybdenum disulfide layer;

[0026] (4) coating photoresist on the surface of the second substrate, and patterning the photoresist;

[0027] (5) growing metal on the surface of the photoresist by a vapor deposition process, and removing the photoresist and the metal on the photoresist after vapor deposition to obtain a metal electrode layer and a part of the NAND output end;

[0028] (6) growing metal on the surface of the sample by a vapor deposition process, and growing metal oxide on the surface of the sample by an atomic layer deposition process;

[0029] (7) coating photoresist on the surface of the metal oxide, and patterning the photoresist;

[0030] (8) etching the metal oxide, and removing the photoresist on the surface of the metal oxide after etching to obtain a first insulating layer and a second insulating layer;

[0031] (9) coating a layer of photoresist on the surface of the sample, and patterning the photoresist;

[0032] (10) growing metal on the surface of the sample by a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a NAND input end and a remaining part of the NAND output end, and the preparation of the molybdenum disulfide NAND array is completed.

[0033] The above technical features can be combined with each other as long as they do not conflict with each other.

[0034] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0035] The micro multi-ion sensing system based on the NAND array of the present application can detect multiple ions simultaneously through the design of the array structure in the system, which meets the actual detection requirements and is convenient for large-scale preparation of the sensor; the Nand structure breaks the Nernst limit, which can accurately detect the small changes of ion concentration and has higher sensitivity; the NAND output voltage is in the order of volts, which is convenient for measurement and avoids the measurement of small current, simplifies the circuit, and is more conducive to subsequent processing of the signal, and is easy to realize the miniaturization of the sensing system; the molybdenum disulfide is used as the channel material of the NAND due to its large band gap, a field effect transistor with small channel current and strong gate control ability is prepared, and a low-power and high-gain NAND array is built, which can effectively reduce the size and power consumption of the NAND, improve the integration of the sensing system, and prolong the service life of the sensing system. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the accompanying drawings needed in the embodiments will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0037] Figure 1 is a schematic diagram of the overall structure of the micro multi-ion sensing system based on the NAND gate array in the embodiments of the present application;

[0038] Figure 2 is a schematic diagram of the top view structure of the micro multi-ion sensing system based on the NAND gate array in the embodiments of the present application;

[0039] Figure 3 is a transfer characteristic curve of the MoS2 field effect transistor formed in the micro multi-ion sensing system based on the NAND gate array in the embodiments of the present application;

[0040] Figure 4 is a transfer characteristic curve of the MoS2 NAND gate in the micro multi-ion sensing system based on the NAND gate array in the embodiments of the present application;

[0041] Figure 5 is a gain curve of the MoS2 NAND gate in the micro multi-ion sensing system based on the NAND gate array in the embodiments of the present application.

[0042] In all the drawings, the same reference signs represent the same technical features, specifically: 1, MoS2 NAND gate; 11, NAND gate input end; 12, NAND gate output end; 13, first insulating layer; 14, second insulating layer; 15, first MoS2 layer; 16, second MoS2 layer; 17, second metal electrode; 18, third metal electrode; 19, second substrate; 2, multi-ion sensing unit; 21, liquid storage pool; 22, ion sensitive film; 23, first metal electrode; 24, first substrate. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0044] In the description of the present application, it is to be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0045] In addition, unless explicitly specified and limited, the terms "first", "second" are only for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated thereby. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless explicitly specified and limited.

[0046] In the present application, unless explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] In the present application, unless explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0048] Embodiment:

[0049] Please refer to Figures 1-5The micro multi-ion sensing system based on the non-gate array in the preferred embodiment of the present application comprises a molybdenum disulfide non-gate array and a multi-ion sensing unit 2 connected to each other, so as to detect the concentrations of multiple ions in a to-be-detected solution through the multi-ion sensing unit 2 at the same time, and convert the concentrations of the multiple ions into an electrical signal output through the molybdenum disulfide non-gate array.

[0050] Specifically, as shown in FIG. 1, Figure 1 The multi-ion sensing unit 2 in the preferred embodiment comprises, from top to bottom, a liquid storage pool 21, an ion-sensitive film array, a metal electrode array and a first substrate 24.

[0051] The liquid storage pool 21 is a cylindrical structure with both ends open, and one end is fixedly arranged on the first substrate 24 and used for storing a to-be-detected solution; the metal electrode array is arranged on the first substrate 24 and arranged in the liquid storage pool 21, and specifically comprises multiple first metal electrodes 23; the ion-sensitive film array comprises multiple ion-sensitive films 22, each ion-sensitive film 22 is arranged on each first metal electrode 23 one by one, each ion-sensitive film 22 contains an ion carrier, and different ion-sensitive films 22 contain different ion carriers, so as to detect the concentrations of multiple ions in the to-be-detected solution in the liquid storage pool 21.

[0052] More specifically, the material of the liquid storage pool 21 is any one of polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA). The material of each first metal electrode 23 in the metal electrode array is related to the type of to-be-detected ion. If the to-be-detected ion is a hydrogen ion (i.e. the pH value of the solution is measured), the material of the first metal electrode 23 is TiN (titanium nitride), and the thickness is preferably 20-100 nm, and no ion-sensitive film 22 is arranged on the first metal electrode 23; if the to-be-detected ion is another ion, the metal electrode array is a double-layer metal stacking structure, wherein the material of the lower layer metal is selected from any one of Ti (titanium) and Cr (chromium), and the thickness is preferably 5-10 nm; the material of the upper layer metal is Au (gold), and the thickness is preferably 20-30 nm. The first substrate 24 is a SiO2 / Si (silicon dioxide / silicon) substrate, wherein the thickness of SiO2 in the SiO2 / Si substrate is preferably 200-300 nm.

[0053] As shown in FIG. 1, Figure 2 The metal electrode array in the preferred embodiment comprises four first metal electrodes 23, one of which is made of TiN and used for detecting the concentration of hydrogen ions; the other three first metal electrodes 23 have ion-sensitive films 22 containing different ion carriers arranged above them, forming a multi-ion sensing unit 2 capable of simultaneously detecting the concentrations of four ions.

[0054] Further, as shown in FIG. 1, Figure 1As shown in the figure, the molybdenum disulfide NOT gate array in the preferred embodiment comprises a plurality of molybdenum disulfide NOT gates 1 arranged on the second substrate 19, the number of the molybdenum disulfide NOT gates 1 corresponding to the number of ions that can be detected by the multi-ion sensitive unit 2.

[0055] Specifically, the molybdenum disulfide NOT gate 1 comprises a metal electrode layer, a molybdenum disulfide layer, an insulating layer, a NOT gate input end 11 and a NOT gate output end 12, the molybdenum disulfide layer, the metal electrode layer and the NOT gate output end 12 being arranged on the second substrate 19. The metal electrode layer comprises a second metal electrode 17 and a third metal electrode 18 arranged on both sides of the NOT gate output end 12 and spaced apart from the NOT gate output end 12; the molybdenum disulfide layer comprises a first molybdenum disulfide layer 15 and a second molybdenum disulfide layer 16, wherein the first molybdenum disulfide layer 15 is arranged between the second metal electrode 17 and the NOT gate output end 12, and both ends thereof are connected with the second metal electrode 17 and the NOT gate output end 12 respectively, and the second molybdenum disulfide layer 16 is arranged between the third metal electrode 18 and the NOT gate output end 12, and both ends thereof are connected with the third metal electrode 18 and the NOT gate output end 12 respectively.

[0056] Meanwhile, a first insulating layer 13 is arranged on one side of the NOT gate output end 12, the first molybdenum disulfide layer 15 and the second metal electrode 17, and the NOT gate input end 11 is arranged on the first insulating layer 13; a second insulating layer 14 is arranged on the other side of the NOT gate output end 12, the second molybdenum disulfide layer 16 and the third metal electrode 18, and one end of the NOT gate output end 12 away from the second substrate 19 is arranged on the second insulating layer 14.

[0057] Correspondingly, each first metal electrode 23 in the metal electrode array is connected with the NOT gate input end 11 in the molybdenum disulfide NOT gate array through a wire.

[0058] It can be understood that the above-mentioned molybdenum disulfide NOT gate 1 constitutes two n-type molybdenum disulfide field effect transistors, as shown in the figure. Figure 1 As shown in the figure, the NOT gate input end 11, the second metal electrode 17 and the NOT gate output end 12 form the gate, the source and the drain of the first transistor respectively; meanwhile, one end of the NOT gate output end 12 away from the second substrate 19, one end of the NOT gate output end 12 close to the second substrate 19 and the third metal electrode 18 form the gate, the source and the drain of the second transistor respectively.

[0059] In actual work of the molybdenum disulfide NOT gate 1, the second metal electrode 17 is grounded, and a fixed positive voltage is applied to the third metal electrode 18, then the output voltage of the NOT gate output end 12 will change with the input voltage of the NOT gate input end 11; when the input voltage of the NOT gate input end 11 is less than a certain threshold (V th1), the first transistor is in the off state and the second transistor is in the on state. At this time, the resistance of the first transistor is much greater than the resistance of the second transistor, and the output voltage of the NOT gate output terminal 12 is substantially consistent with the voltage of the third metal electrode 18. When the input voltage of the NOT gate input terminal 11 is greater than a certain threshold (V th2 ), the first transistor is in the on state and the second transistor is in the off state. At this time, the resistance of the second transistor is much greater than the resistance of the first transistor, and the output voltage of the NOT gate output terminal 12 is substantially consistent with the voltage of the second metal electrode 17; when the input voltage of the NOT gate input terminal 11 is greater than V th1 and less than V th2 When , the output voltage of the NOT gate output terminal 12 will change sharply along with the input voltage of the NOT gate input terminal 11 .

[0060] After the test solution is injected into the liquid reservoir 21, according to the Nernst equation, the membrane potential of the ion-sensitive film 22 will change with the change of the corresponding ion concentration (for example, the membrane potential of the sodium ion-sensitive film 22 will increase with the increase of the sodium ion concentration in the solution), and the change in membrane potential ΔV1 will be transmitted to the NOT gate input terminal 11 through the first metal electrode 23. If the voltage of the NOT gate input terminal 11 is at V before and after the change, th1 With V th2 Then a small change ΔV1 in the voltage at the NOT gate input 11 will cause a large change ΔV2 in the voltage at the NOT gate output 12, thereby amplifying and outputting the detection signal. The actual membrane potential change can then be calculated based on the output detection signal, and the corresponding ion concentration in the solution can be deduced.

[0061] Preferably, the molybdenum disulfide layer is a single atomic layer single atomic layer single crystal structure, and its thickness is 0.5-1 nm, more preferably 0.7 nm.

[0062] Preferably, the first insulating layer 13 and the second insulating layer 14 are made of any one of aluminum oxide, hafnium oxide, and silicon dioxide, and have a thickness of 30-50 nanometers.

[0063] Preferably, the NOT gate input terminal 11, the NOT gate output terminal 12 and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower metal layer is any one of Ti and Cr, with a thickness of 5~10nm, and the material of the upper metal layer is any one of Au, Ag (silver), Cu (copper), Pd (palladium), Pt (platinum), with a thickness of 20~30nm.

[0064] Preferably, the second substrate 19 is a SiO 2 / Si substrate, wherein the thickness of SiO 2 in the SiO 2 / Si substrate is 200-300 nm.

[0065] Further, the present application also relates to a preparation method of the multi-ion sensitive unit, which is used for preparing the multi-ion sensitive unit 2 and specifically includes the following steps:

[0066] (1) coating photoresist on the surface of the first substrate 24 and patterning the photoresist;

[0067] Specifically, a layer of negative photoresist is spin-coated on the surface of the sample by using a spin coater at a speed of 700-3000 rpm for 9-40 seconds, and then pre-baked on a hot plate at 120℃ for 2 minutes, and then patterned by exposing for 20 seconds, middle baking at 120℃ for 2 minutes, and immersing in a developing solution for 1 minute.

[0068] (2) growing metal on the surface of the photoresist by using a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array;

[0069] Specifically, 5-10 nm Ti and 20-30 nm thick Au are grown on the surface of the sample by using a sputtering process. After sputtering, the sample is immersed in acetone to remove the photoresist and the metal on the photoresist, thereby preparing a metal electrode array.

[0070] (3) dropping each ion carrier and its corresponding sensitive solution on the surface of its corresponding first metal electrode 23 respectively and drying to obtain an ion sensitive film array;

[0071] Taking the preparation of the sodium ion sensitive film 22 as an example, 10 mg of sodium ion carrier X, 5.5 mg of sodium tetrakis(3,5-di(trifluoromethyl)phenyl)borate (Na-TFPB), 330 mg of polyvinyl chloride (PVC), and 654.5 mg of dioctyl sebacate (DOS) are dissolved in 6.6 ml of tetrahydrofuran (THF), stirred uniformly, and placed in a 4℃ refrigerator for 24 h; 2 μl of the above mixture is dropped on the surface of the first metal electrode 23, and dried in air for 24 h to obtain the sodium ion sensitive film 22.

[0072] Correspondingly, when preparing other ion sensitive films 22, only the above sodium ion carrier X is replaced by other ion carriers such as valinomycin (potassium ion carrier), calcium ion carrier II, etc., and the sensitive solution of other ions is configured, dropped on the surface of the first metal electrode 23 and dried to obtain the corresponding ion sensitive film 22.

[0073] (4) bonding the liquid pool 21 on the first substrate 24 to complete the preparation of the multi-ion sensitive unit 2.

[0074] The liquid pool 21 of polymethyl methacrylate (PMMA) is processed by using a numerical control machine tool, and the liquid pool 21 is bonded on the first substrate 24 by using glue.

[0075] Furthermore, the present invention also relates to a method for preparing a molybdenum disulfide NOT gate array, which specifically comprises the following steps:

[0076] (1) growing a monolayer of molybdenum disulfide on the surface of the second substrate 19 by chemical vapor deposition;

[0077] (2) coating a photoresist on the surface of molybdenum disulfide and patterning the photoresist;

[0078] In a preferred embodiment, a layer of positive photoresist is spin-coated on the surface of the SiO2 / Si substrate using a coater, the coater speed is 500~1000 rpm, the spin coating time is 9~40 seconds, and it is pre-baked on a 110°C hot plate for 2 minutes, and then exposed for 20 seconds, baked at 90°C for 1 minute, immersed in a developer for 1 minute, and post-baked at 110°C for 2 minutes to make it patterned.

[0079] (3) etching the molybdenum disulfide and removing the photoresist on the surface of the single-layer molybdenum disulfide after etching to obtain a molybdenum disulfide layer;

[0080] In a preferred embodiment, an oxygen plasma etcher is used to etch a single layer of molybdenum disulfide. The etcher has a flow rate of 500 sccm, a power of 200 W, and an etching time of 4 min. After etching, the sample is immersed in an acetone solution to remove the positive photoresist on the surface of the molybdenum disulfide to prepare a molybdenum disulfide layer.

[0081] (4) coating a photoresist on the surface of the second substrate 19 and patterning the photoresist;

[0082] In a preferred embodiment, a layer of negative photoresist is spin-coated on the surface of the second substrate 19 using a coating machine, wherein the rotation speed of the coating machine is 700~3000 rpm, the spinning time is 9~40 seconds, and after spin coating, it is baked on a 120℃ hot plate for 2 minutes, and then exposed for 20 seconds, baked at 120℃ for 2 minutes, and immersed in a developer for 1 minute to make it patterned.

[0083] (5) growing metal on the surface of the photoresist by an evaporation process, and removing the photoresist and the metal on the photoresist after evaporation to obtain a metal electrode layer and a portion of the NOT gate output terminal 12;

[0084] In a preferred embodiment, a 5-10 nanometer thick layer of Ti and a 20-30 nanometer thick layer of Au are grown on the sample surface using an evaporation process. After evaporation, the sample is immersed in acetone to remove the photoresist and the metal on it, thereby forming the second metal electrode 17, the third metal electrode 18, and a portion of the NOT gate output terminal 12.

[0085] (6) Using evaporation technology to grow metal on the sample surface, and using atomic layer deposition technology to grow metal oxide on the sample surface;

[0086] In the preferred embodiment, 1 nm of Al is grown on the sample surface by evaporation; then, the sample is left to stand in air for at least 3 h, and 30 nm of Al2O3 is grown on the sample surface by atomic layer deposition.

[0087] (7) coating photoresist on the surface of the metal oxide and patterning the photoresist;

[0088] A layer of negative photoresist is spin-coated on the sample surface by using a spin coater at a speed of 700-3000 rpm for 9-40 s, and pre-baked on a hot plate at 120°C for 2 min; then, the photoresist is patterned by exposure for 20 s, middle baking at 120°C for 2 min, soaking in a developing solution for 1 min, and post-baking at 120°C for 2 min.

[0089] (8) etching the metal oxide, and removing the photoresist on the surface of the metal oxide after etching to obtain the first insulating layer 13 and the second insulating layer 14;

[0090] In the preferred embodiment, the sample is soaked in the developing solution, and taken out every 5 min for washing with deionized water until the surface Al2O3 is completely etched. After etching, the sample is soaked in acetone to remove the photoresist on the surface of the Al2O3, thereby preparing the first insulating layer 13 and the second insulating layer 14.

[0091] (9) spin-coating a layer of photoresist on the sample surface and patterning the photoresist;

[0092] In the preferred embodiment, a layer of negative photoresist is spin-coated on the sample surface by using a spin coater at a speed of 700-3000 rpm for 9-40 s, and pre-baked on a hot plate at 120°C for 2 min; then, the photoresist is patterned by exposure for 20 s, middle baking at 120°C for 2 min, soaking in a developing solution for 1 min, and post-baking at 120°C for 2 min.

[0093] (10) growing metal on the sample surface by sputtering, and removing the photoresist and the metal on the photoresist after sputtering to obtain the NAND gate input end 11 and the NAND gate output end 12 of the remaining part, thereby completing the preparation of the MoS2 NAND gate array.

[0094] In the preferred embodiment, 5-10 nm of Ti and 20-30 nm of Pd are grown on the sample surface by sputtering. After sputtering, the sample is soaked in acetone to remove the negative photoresist and the metal on the negative photoresist, thereby preparing the NAND gate input end 11 and the NAND gate output end 12 of the remaining part.

[0095] Further, in the preferred embodiment, the electrical properties of the MoS2 NAND gate array are tested.

[0096] The second metal electrode 17, the NOT gate output end 12 and the NOT gate input end 11 are respectively taken as the source, the drain and the gate of the molybdenum disulfide field effect transistor, and the transfer characteristic curve of the molybdenum disulfide field effect transistor is tested, as shown in Figure 3 The prepared molybdenum disulfide field effect transistor is n-type, the on-off ratio reaches 10 5 , the subthreshold swing is about 400 mV / dec, and the gate control ability is good.

[0097] The NOT gate input end 11, the NOT gate output end 12, the second metal electrode 17 and the third metal electrode 18 are respectively taken as the input end, the output end, the ground end and the power supply end of the NOT gate, and the transfer characteristic curve of the molybdenum disulfide NOT gate 1 is tested, as shown in Figure 4 When the input voltage is less than -2V, the output voltage is close to the voltage of the power supply end; when the input voltage is greater than -1.5V, the output voltage is about 0V, and the NOT gate on-off characteristic is good.

[0098] Figure 5 The NOT gate gain curve calculated based on Figure 4 When the input voltage is in the interval of about -1.8V to -1.6V, the NOT gate gain is greater than 1, and the detection of the super Nernst limit can be realized.

[0099] Compared with the method for detecting ion concentration by using a field effect transistor, the ion sensing system based on the NOT gate array structure in the application can break through the Nernst limit and can simultaneously measure multiple ion concentrations with super high sensitivity. Since the output of the NOT gate is voltage, the measurement of a small current is avoided, and the subsequent signal processing is more convenient.

[0100] The NOT gate array prepared by the micro multi-ion sensing system based on the NOT gate array and the preparation method thereof adopts single-layer MoS2 as a channel material, the lateral dimension is micron level, and the thickness is nanometer level, so that the overall size of the device is greatly reduced, and a sensing system with higher integration can be realized. Compared with the NOT gate based on a silicon-based field effect transistor, the NOT gate based on the MoS2 field effect transistor has smaller opening voltage and on-state current, and the overall power consumption is only microwatt level. The sodium ion sensing system based on the NOT gate structure is more suitable for high-sensitivity, long-term and real-time monitoring of ion concentration in the human body.

[0101] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A micro multi-ion sensing system based on a NOT gate array, characterized in that: Including multiple ion sensitive units and molybdenum disulfide NOT gate array; The multi-ion sensitive unit includes a metal electrode array, an ion sensitive film array and a liquid reservoir; the liquid reservoir is arranged on a first substrate and is used to store a solution to be tested; the metal electrode array is arranged on the first substrate and in the liquid reservoir, and includes a plurality of first metal electrodes; The ion-sensitive film array includes a plurality of ion-sensitive films disposed on each of the first metal electrodes, and different ion-sensitive films contain different ion carriers; The MoS2 NOT gate array comprises a plurality of MoS2 NOT gates arranged on a second substrate; The molybdenum disulfide NOT gate comprises a metal electrode layer, a molybdenum disulfide layer, a NOT gate input terminal and a NOT gate output terminal; the NOT gate output terminal, the molybdenum disulfide layer and the metal electrode layer are arranged on the second substrate, the molybdenum disulfide layer comprises a first molybdenum disulfide layer and a second molybdenum disulfide layer; the metal electrode layer comprises a second metal electrode and a third metal electrode spaced apart and arranged on both sides of the NOT gate output terminal, one end of the first molybdenum disulfide layer is connected to the second metal electrode, and the other end is connected to the NOT gate output terminal; one end of the second molybdenum disulfide layer is connected to the third metal electrode, and the other end is connected to the NOT gate output terminal; a first insulating layer is arranged on one side of the NOT gate output terminal, the first molybdenum disulfide layer and the second metal electrode, and the NOT gate input terminal is arranged on the first insulating layer; a second insulating layer is arranged on the other side of the NOT gate output terminal, the second molybdenum disulfide layer and the third metal electrode, and the NOT gate output terminal extends from the second substrate and is arranged on the second insulating layer; Each of the first metal electrodes in the metal electrode array is connected to each of the NOT gate input terminals in the molybdenum disulfide NOT gate array in a one-to-one correspondence.

2. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The molybdenum disulfide layer is a single atomic layer single crystal structure with a thickness of 0.5-1 nm.

3. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The first insulating layer and the second insulating layer are made of any one of aluminum oxide, hafnium oxide, and silicon dioxide, and have a thickness of 30-50 nm.

4. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The NOT gate input end, the NOT gate output end and the metal electrode layer are all double-layer metal stack structures; wherein the material of the lower metal layer is any one of Ti and Cr, with a thickness of 5~10nm, and the material of the upper metal layer is any one of Au, Ag, Cu, Pd, Pt, with a thickness of 20~30nm.

5. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: When the ion to be measured is a hydrogen ion, the corresponding first metal electrode is made of TiN with a thickness of 20 to 100 nm, and no ion-sensitive film is provided on the first metal electrode; when the ion to be measured is other ions, the corresponding first metal electrode is a double-layer metal stack structure, wherein the lower metal is any one of Ti and Cr with a thickness of 5 to 10 nm, and the upper metal is Au with a thickness of 20 to 30 nm.

6. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The first substrate and the second substrate are both SiO2 / Si substrates, and the thickness of SiO2 in the SiO2 / Si substrate is 200-300 nm.

7. The micro multi-ion sensing system based on a NOT gate array according to claim 1, characterized in that: The material of the liquid storage tank is any one of polydimethylsiloxane and polymethyl methacrylate.

8. A method for preparing a multi-ion sensitive unit, used for preparing the multi-ion sensitive unit in the micro multi-ion sensing system based on a NOT gate array according to any one of claims 1 to 7, characterized in that: The steps include: (1) coating a photoresist on the surface of the first substrate and patterning the photoresist; (2) growing metal on the surface of the photoresist using a sputtering process, and removing the photoresist and the metal on the photoresist after sputtering to obtain a metal electrode array; (3) dropping each ion carrier and its corresponding sensitive solution onto the surface of its corresponding first metal electrode and drying them to obtain an ion-sensitive thin film array; (4) Bonding the liquid reservoir to the first substrate to complete the preparation of the multi-ion sensitive unit.

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