Ion generating device and ion mobility analyzing device

Abstract

An ion generating device capable of generating positive ions using an electron emitting element is provided. The ion generating device of the present invention comprises: an electron emitting element, an opposing electrode, and a control unit, wherein the electron emitting element comprises: a lower electrode; a surface electrode; and an intermediate layer arranged between the lower electrode and the surface electrode, the opposing electrode is arranged in a manner opposite to the surface electrode, and the control unit is configured to: apply a voltage to the surface electrode, the lower electrode, or the opposing electrode, so that in a positive ion mode for generating positive ions, the potential of the surface electrode is higher than the potential of the lower electrode and the potential of the opposing electrode.

Description

Technical Field

[0001] The present invention relates to an ion generating device and an ion mobility analyzing device. Background Art

[0002] The electron emission element is an ion source capable of emitting low-energy electrons, and the emitted low-energy electrons can negatively ionize the target material. An ion generator using such an electron emission element is known (for example, see Patent Document 1). In the ion generator, a high voltage is applied between a needle electrode and a plate electrode to generate a corona discharge in order to generate positive ions.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-214443 Summary of the invention

[0006] Technical Problems to be Solved by the Invention

[0007] Since positive ions are not generated by the attachment of low-energy electrons emitted from the electron emitting element, when used as an ion source for an analytical device that requires both negative and positive ionization (such as an ion mobility spectrometer (IMS, Ion mobility spectrometry)), it is necessary to combine it with an ion source that can positively ionize (such as a radiation source, corona discharge, UV light source, etc.), which leads to the problem of large-scale equipment.

[0008] The present invention has been made in view of such circumstances, and provides an ion generating device capable of generating positive ions using an electron emitting element.

[0009] Technical solutions for solving technical problems

[0010] The present invention provides an ion generating device, comprising: an electron emitting element, an opposing electrode and a control unit, wherein the electron emitting element includes: a lower electrode; a surface electrode; and an intermediate layer arranged between the lower electrode and the surface electrode, the opposing electrode is arranged in a manner opposite to the surface electrode, and the control unit is configured to: apply a voltage to the surface electrode, the lower electrode or the opposing electrode so that in a positive ion mode for generating positive ions, the potential of the surface electrode is higher than the potential of the lower electrode and the potential of the opposing electrode.

[0011] Beneficial Effects

[0012] The control unit applies a voltage to the surface electrode or the lower electrode so that the potential of the surface electrode is higher than the potential of the lower electrode, so that electrons flow from the lower electrode to the surface electrode and emit electrons from the surface electrode. In addition, by sufficiently increasing the potential difference between the surface electrode and the lower electrode, the electrons emitted from the surface electrode can have an energy higher than the ionization energy of the first gas component, and the first gas component near the surface electrode can be positively ionized. The control unit applies a voltage to the surface electrode or the opposing electrode so that the potential of the surface electrode is higher than the potential of the opposing electrode, so that the positive ions generated near the surface electrode can move to the opposing electrode. Thus, it is possible to suppress the positive ions from being recovered to the surface electrode near the surface electrode, the electrons emitted from the electron emission element, etc., from being attached to the positive ions to neutralize the positive ions, and the positive ions moving between the surface electrode and the opposing electrode can be used as an analysis object, etc. In addition, the generated positive ions can transmit positive charges to the second gas component and positively ionize the second gas component. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic cross-sectional view of an ion generating device according to one embodiment of the present invention.

[0014] Figure 2 This is a schematic cross-sectional view of an ion generating device according to one embodiment of the present invention.

[0015] Figure 3 This is a schematic cross-sectional view of an ion mobility analysis device according to one embodiment of the present invention.

[0016] Figure 4 This is a schematic cross-sectional view of an ion mobility analysis device according to one embodiment of the present invention.

[0017] Figure 5 This is a schematic cross-sectional view of an ion mobility analysis device according to one embodiment of the present invention.

[0018] Figure 6 This is a schematic cross-sectional view of an ion mobility analysis device according to one embodiment of the present invention.

[0019] Figure 7 It is an IMS spectrum measured using positive ion detection experiments.

[0020] Figure 8 It is an IMS spectrum measured using positive ion detection experiments.

[0021] Fig. 9 It is an IMS spectrum measured using positive ion detection experiments.

[0022] Fig.10 This is an IMS spectrum measured using a negative ion detection experiment.

[0023] Fig.11 This is an IMS spectrum measured using a negative ion detection experiment.

[0024] Fig.12 This is an IMS spectrum measured using a negative ion detection experiment.

[0025] Fig.13 This is an IMS spectrum measured using an ethanol analysis experiment. DETAILED DESCRIPTION

[0026] The ion generating device of the present invention comprises an electron emitting element, an opposing electrode and a control unit, wherein the electron emitting element comprises: a lower electrode, a surface electrode, and an intermediate layer arranged between the lower electrode and the surface electrode, wherein the opposing electrode is arranged in a manner opposite to the surface electrode, and the control unit applies voltage to the surface electrode, the lower electrode and the opposing electrode so that in a positive ion mode for generating positive ions, the potential of the surface electrode is higher than the potential of the lower electrode and the potential of the opposing electrode.

[0027] The control unit is preferably configured to apply a voltage between the lower electrode and the surface electrode so that in the positive ion mode, electrons with energy higher than the ionization energy of the gas component between the surface electrode and the opposing electrode are emitted from the electron emission element. By colliding the emitted electrons with the gas component near the surface electrode, one electron can be removed from the gas component, and positive ions of the gas component can be generated. The control unit is preferably configured to apply a voltage of more than 16V and less than 60V between the lower electrode and the surface electrode in the positive ion mode. Thus, positive ions can be generated between the surface electrode and the opposing electrode.

[0028] The control unit is configured to apply a voltage to the surface electrode, the lower electrode or the opposing electrode so that in a negative ion mode for generating negative ions, the potential of the surface electrode is higher than the potential of the lower electrode and lower than the potential of the opposing electrode. In addition, the control unit is preferably configured to be able to switch between the negative ion mode and the positive ion mode. Thus, both negative ions and positive ions can be generated using the ion generating device. The control unit is preferably configured to apply a voltage of more than 6V and less than 60V between the lower electrode and the surface electrode in the negative ion mode. Thus, negative ions can be generated between the surface electrode and the opposing electrode.

[0029] The present invention also provides an ion mobility analysis device having an ion generating device, an ion detector and an electric field forming electrode of the present invention. The ion detector and the control unit are configured to measure the current generated by the ion detector receiving the charge from the ions and output an IMS spectrum. The control unit is preferably configured to adjust the voltage applied between the lower electrode and the surface electrode so that the reference peak appearing in the IMS spectrum is a specified height or a specified area. Thus, the sample gas can be quantitatively analyzed based on the peak area or peak height of the IMS spectrum.

[0030] The control unit is preferably configured to adjust the voltage applied between the lower electrode and the surface electrode so that the height or area of ​​the first reference peak appearing in the IMS spectrum in the positive ion mode is substantially the same as the height or area of ​​the second reference peak appearing in the IMS spectrum in the negative ion mode. Thus, it is possible to use the peak appearing in the IMS spectrum in the positive ion mode and the peak appearing in the IMS spectrum in the negative ion mode to perform qualitative analysis and quantitative analysis. The control unit preferably changes the potential of the surface electrode to a potential with opposite polarity and substantially equal absolute value when switching the negative ion mode and the positive ion mode, and changes the potential of the lower electrode to a potential with opposite polarity and different absolute value. Thus, it is possible to switch the negative ion mode and the positive ion mode while maintaining the potential of the ion collector at 0V. In addition, by changing the potential of the lower electrode to a potential with opposite polarity and different absolute value, it is possible to prevent electrons from being emitted from the electron emitting element.

[0031] The present invention will be described in more detail below with reference to a plurality of embodiments. The configurations shown in the drawings and the following description are examples, and the scope of the present invention is not limited to the contents shown in the drawings and the following description.

[0032] First embodiment

[0033] Figure 1 is a schematic cross-sectional view of an ion generating device in a positive ion mode. Figure 2 2 is a schematic cross-sectional view of an ion generating device in a negative ion mode. The ion generating device 30 of the present embodiment includes an electron emitting element 2, an opposing electrode 6, and a control unit 7. The electron emitting element 2 includes a lower electrode 3, a surface electrode 5, and an intermediate layer 4 disposed between the lower electrode 3 and the surface electrode 5. The opposing electrode 6 is disposed opposite to the surface electrode 5. The control unit 7 is configured to apply a voltage to the surface electrode 5, the lower electrode 3, or the opposing electrode 6 so that in a positive ion mode for generating positive ions, the potential of the surface electrode 5 is higher than the potential of the lower electrode 3 and the potential of the opposing electrode 6.

[0034] The ion generating device 30 is a device for generating ions in a space (in the air, in a gas, in a reduced pressure atmosphere, etc.) between the surface electrode 5 and the counter electrode 6. The ion generating device 30 has a positive ion mode for generating positive ions. In addition, the ion generating device 30 can have a negative ion mode for generating negative ions. In addition, the ion generating device 30 can be configured to switch between the positive ion mode and the negative ion mode. The ion generating device 30 can also be assembled into an ion mobility analysis device.

[0035] The electron emission element 2 is an element that emits electrons from an electron emission region of a surface electrode 5 into the air, a gas, a reduced pressure atmosphere, etc. The electron emission element 2 includes a lower electrode 3, a surface electrode 5, and an intermediate layer 4 disposed between the lower electrode 3 and the surface electrode 5. In addition, the electron emission element 2 may include an insulating layer that defines an electron emission region.

[0036] The lower electrode 3 is an electrode located on the lower side of the intermediate layer 4. The lower electrode 3 can be a metal substrate or a conductive material layer (metal layer, conductor layer, etc.) provided on an insulating substrate (or semiconductor substrate). In the case where the lower electrode 3 is composed of a metal substrate, the lower electrode 3 is, for example, an aluminum plate, a stainless steel plate, a nickel plate, etc. The thickness of the lower electrode 3 is preferably greater than 200 μm and less than 1 mm. In the case where the lower electrode 3 is a conductive material layer and is provided on an insulating substrate (or semiconductor substrate), the substrate is, for example, a glass substrate, a resin substrate, a ceramic substrate, etc. The thickness of the substrate is preferably greater than 200 μm and less than 2 mm.

[0037] When the lower electrode 3 is a conductive material layer, the lower electrode 3 can be formed on the substrate by, for example, sputtering, evaporation, electroplating, CVD, etc. The lower electrode 3 can be a single-layer electrode or a stacked electrode. The lower electrode 3 can include, for example, an aluminum layer, a gold layer, a copper layer, etc. In addition, the lower electrode 3 can also be a Mo / Al / Mo stacked electrode. The thickness of the lower electrode 3 is preferably greater than 200 nm and less than 1 μm.

[0038] The insulating layer is a layer composed of an insulator provided on the lower electrode 3. For example, when the lower electrode 3 is an aluminum substrate, the insulating layer may also be an oxide film of the aluminum substrate. For example, when the lower electrode 3 is provided on a substrate, the insulating layer may be, for example, a silicon nitride layer (SiN layer), a silicon oxide layer (SiO 2 layer), silicon oxynitride film (SiON film), aluminum oxide layer (Al 2 O 3 ) etc. The thickness of the insulating layer is preferably 0.5 μm or more and 2 μm or less. The insulating layer can be formed using, for example, photolithography, sputtering or CVD.

[0039] The insulating layer has an opening that becomes an electron emission region. The electron emission region is a region where electrons flow from the lower electrode 3 toward the surface electrode 5 in the intermediate layer 4 by an inhomogeneous electric field generated between the lower electrode 3 and the surface electrode 5, and electrons are emitted from the surface electrode 5 to the outside. The intermediate layer 4 is provided in the opening. Thus, current can flow only in the region of the intermediate layer 4 overlapping with the opening, and electrons can be emitted from the region of the surface electrode 5 overlapping with the opening of the insulating layer. Therefore, the electron emission region can be determined by the opening of the insulating layer.

[0040] The intermediate layer 4 is provided on the lower electrode 3. The intermediate layer 4 is a layer that allows current to flow through an inhomogeneous electric field formed by the potential difference between the surface electrode 5 and the lower electrode 3. The intermediate layer 4 is, for example, an insulating resin layer having conductive particles in a dispersed state. The conductive particles contained in the intermediate layer 4 may use conductive metal particles such as gold, silver, platinum or palladium. In addition, as conductive materials other than metal particles, carbon, conductive polymers and / or semiconductive materials may also be used. The insulating resin contained in the intermediate layer 4 may be, for example, a silanol (R 3 The conductive particles are dispersed in the insulating resin, but part of the conductive particles may also be aggregated. In the intermediate layer 4, the content of the conductive particles can be appropriately changed. By changing the content of the conductive particles, the resistance value of the intermediate layer can be adjusted.

[0041] The thickness of the intermediate layer 4 is not particularly limited, but is preferably 0.5 μm to 2.0 μm, and more preferably 0.75 μm to 1.5 μm. Thus, a relatively low voltage is applied between the lower electrode 3 and the surface electrode 5, so that electrons can be emitted from the electron emitting element 2, and the life characteristics of the electron emitting element 2 can be improved.

[0042] The intermediate layer 4 is formed by a coating method such as a spin coating method, a doctor blade method, a spray coating method or a dipping method. An example of a method for making the intermediate layer 4 is described. First, 3 g of a silicone resin as a resin and 0.03 g of Ag nanoparticles as conductive particles are placed in a reagent bottle and mixed. As a result, a mixed solution of silicone resin and Ag nanoparticles is prepared. Next, an ultrasonic vibrator is used to further stir the mixed solution loaded in the reagent bottle to prepare a coating solution. The viscosity of the coating solution is preferably 0.8 to 15 mPa·s. The ratio of the resin component in the coating solution is preferably about 10 to 70 wt%. After the coating solution is applied to the lower electrode 3, it is polycondensed by moisture in the atmosphere to become a silicone resin, forming the intermediate layer 4.

[0043] The surface electrode 5 is an electrode located on the surface of the electron emission element 2, and is arranged on the intermediate layer 4 and the insulating layer. The surface electrode 5 is, for example, a single-layer electrode composed of an Au layer, a single-layer electrode composed of a Pt layer, or a stacked electrode composed of an Au layer and a Pt layer. The surface electrode 5 can have a thickness of 5 nm or more and 100 nm or less, preferably 40 nm or more and 100 nm or less. In addition, the material of the surface electrode 5 is, for example, a metal material such as gold, platinum, a semiconductor, ITO (Indium tin oxide), a plurality of conductive materials with high conductivity such as carbon, so as to prevent excessive damage as a whole. In addition, the surface electrode 5 can also be composed of multiple metal layers.

[0044] Even when the thickness of the surface electrode 5 is more than 40nm, the surface electrode 5 may also have a plurality of openings, gaps and / or portions thinned to less than 10nm. The electrons flowing out from the intermediate layer 4 can pass through or transmit the openings, gaps and / or thinned portions, and can emit electrons from the surface electrode 5. Such openings, gaps and / or thinned portions are formed by performing a thin film forming process (sputtering, evaporation) accompanied by a general patterning process on the metal constituting the surface electrode 5. In addition, positive ions or negative ions are generated by the electrons emitted from the surface electrode 5.

[0045] The counter electrode 6 is an electrode for forming an electric field between the surface electrode 5 of the electron emitting element 2 and the counter electrode 6. By this electric field, it is possible to suppress the positive ions or negative ions generated near the surface electrode 5 from moving toward the counter electrode 6, and the positive ions or negative ions are neutralized. The counter electrode 6 is arranged to face the surface electrode 5. The counter electrode 6 can be a metal plate, a metal layer, a conductor layer, or a metal mesh electrode.

[0046] The control unit 7 is a part for controlling the ion generating device 30. In addition, the control unit 7 may also be a part for controlling a device (for example, an ion mobility analysis device) in which the ion generating device 30 is assembled. The control unit 7 may include, for example, a microcontroller having a CPU, a memory, a timer, an input / output port, etc. In addition, the control unit 7 may include a power supply unit, a potential control circuit, etc.

[0047] The control unit 7 can control the ion generating device 30 to generate positive ions (positive ion mode) in the space between the surface electrode 5 and the counter electrode 6. The control unit 7 applies a voltage to the surface electrode 5 or the lower electrode 3 so that in the positive ion mode, the potential of the surface electrode 5 is higher than the potential of the lower electrode 3. As a result, electrons flow from the lower electrode 3 to the surface electrode 5, and electrons are released from the electron emission region of the surface electrode 5. In addition, the control unit 7 can apply a voltage between the lower electrode 3 and the surface electrode 5 so that electrons with energy higher than the ionization energy of the gas component between the surface electrode 5 and the counter electrode 6 are emitted from the electron emission element 2 in the positive ion mode. By colliding the emitted electrons with the gas component near the surface electrode 5, one electron can be removed from the gas component, and positive ions of the gas component can be generated.

[0048] In the case of field electron emission, the value (X-5.3) eV obtained by subtracting the work function (5.3 eV) of gold of the surface electrode 5 from the voltage X (V) (element driving voltage) applied between the lower electrode 3 and the surface electrode 5 is considered to be the maximum energy of the emitted electrons.

[0049] For example, when air is present between the surface electrode 5 and the counter electrode 6, the control unit 7 applies a voltage X (V) between the lower electrode 3 and the surface electrode 5, so that electrons with energy higher than the ionization energy of nitrogen, oxygen, water, argon, or carbon dioxide are emitted from the electron emission element 2. For example, when positive ions of water (for example, H) are generated near the surface electrode 5 by the electrons emitted from the electron emission element 2, 3 O + ), the ionization energy of water is 12.6 eV, so a voltage higher than (12.6+5.3)=17.9 V is applied between the lower electrode 3 and the surface electrode 5.

[0050] For example, when ammonia exists between the surface electrode 5 and the counter electrode 6 and ammonia ions (positive ions) are generated near the surface electrode 5 by emitting electrons, the control unit 7 applies a voltage X (V) between the lower electrode 3 and the surface electrode 5 so that electrons with energy higher than the ionization energy of ammonia are emitted from the electron emission element 2. Since the ionization energy of ammonia is 10.1 eV, a voltage higher than (10.1+5.3)=15.4 V is applied between the lower electrode 3 and the surface electrode 5. Therefore, in the positive ion mode, the voltage applied between the lower electrode 3 and the surface electrode 5 can be 16 V or more and 60 V or less, preferably 20 V or more and 40 V or less.

[0051] In addition, the ion generating device 30 may generate positive ions by Penning ionization. In this case, the ion generating device 30 is configured so that neutral atoms or molecules (such as He) exist near the surface electrode 5. Electrons are emitted from the surface electrode 5 of the electron emitting element 2 to neutral atoms or molecules to form a quasi-stable excited state, and ionization is caused by collision with the target substance. A*+B→A+B + +e - , where A* is the electronic excited state of A, B is an atom or molecule, and e - For example, when He is used as the neutral atom for Penning ionization, the energy of the electrons emitted from the electron emitting element is preferably 20 V or more.

[0052] The control unit 7 applies a voltage to the surface electrode 5 or the counter electrode 6 so that in the positive ion mode, the potential of the surface electrode 5 is higher than the potential of the counter electrode 6. The electric field generated by applying this voltage causes the positive ions generated near the surface electrode 5 to move toward the counter electrode 6, and the negative ions generated by the emitted electrons and the emitted electrons to move toward the surface electrode 5. Therefore, the positive ions can be separated from the negative ions and the electrons, and the neutralization of the positive ions can be suppressed. As a result, positive ions can be generated in the space between the surface electrode 5 and the counter electrode 6. In addition, the positive ions can transfer positive charges to other gas components and also generate positive ions of other gas components.

[0053] For example, Figure 1 As shown, the surface electrode 5 is grounded to 0V, and voltages are applied to the lower electrode 3 and the counter electrode 6 by the power supply unit 12 (control unit 7) so that the lower electrode 3 is -20V and the counter electrode 6 is -500V. In this case, electrons flow from the lower electrode 3 to the surface electrode 5 and are emitted from the surface electrode 5. The emitted electrons collide with the gas molecules (or gas atoms) X near the surface electrode 5 (electron collision), generating X + In addition, through the electric field between the surface electrode 5 and the counter electrode 6, X + The electrons move toward the counter electrode 6 and flow toward the surface electrode 5 .

[0054] The control unit 7 can control the ion generating device 30 to generate negative ions in the space between the surface electrode 5 and the counter electrode 6 (negative ion mode). The control unit 7 applies a voltage to the surface electrode 5 or the lower electrode 3 so that in the negative ion mode, the potential of the surface electrode 5 is higher than the potential of the lower electrode 3. As a result, electrons flow from the lower electrode 3 to the surface electrode 5, and electrons are emitted from the electron emission region of the surface electrode 5. In the negative ion mode, the voltage (element driving voltage) applied between the lower electrode 3 and the surface electrode 5 can be 6V or more and 60V or less, preferably 10V or more and 20V or less. By making the energy obtained by the electrons when the electrons are accelerated by the voltage applied between the lower electrode 3 and the surface electrode 5 greater than the work function of gold, electrons can be emitted from the electron emission region of the surface electrode 5. The emitted electrons are attached (electron attachment phenomenon (non-dissociative electron attachment, dissociative electron attachment)) to the gas molecules (or gas atoms) near the surface electrode 5, generating negative ions of the gas molecules (or negative ions of the gas atoms).

[0055] The control unit 7 applies a voltage to the surface electrode 5 or the opposing electrode 6 so that the potential of the surface electrode 5 is lower than the potential of the opposing electrode 6 in the negative ion mode. The negative ions generated near the surface electrode 5 move toward the opposing electrode 6 by the electric field generated by applying the voltage. Thus, negative ions can be generated in the space between the surface electrode 5 and the opposing electrode 6. In addition, the negative ions can transfer negative charges to other gas components and also generate negative ions of other gas components. In addition, in the negative ion mode, even if positive ions are generated near the surface electrode 5, they move toward the surface electrode 5 through the electric field, so it is considered that the emitted electrons are attached to the positive ions and neutralize the positive ions.

[0056] For example, Figure 2 As shown, the surface electrode 5 is connected to the ground and set to 0V, and voltages are applied to the lower electrode 3 and the counter electrode 6 through the power supply unit 12 (control unit 7), so that the lower electrode 3 is -20V and the counter electrode 6 is +500V. In this case, electrons flow from the lower electrode 3 to the surface electrode 5 and are emitted from the surface electrode 5. The emitted electrons attach to the gas molecules (or gas atoms) X near the surface electrode 5, generating X - In addition, through the electric field between the surface electrode 5 and the counter electrode 6, X - Move toward the counter electrode 6.

[0057] The control unit 7 can be set to switch between the positive ion mode and the negative ion mode. Thus, positive ions and negative ions can be generated using one electron emitting element 2. The control unit 7 can switch between the positive ion mode and the negative ion mode by changing the voltage applied to the lower electrode 3, the surface electrode 5 or the counter electrode 6.

[0058] Second embodiment

[0059] The second embodiment relates to a drift tube type ion mobility analyzer in which the ion generating device 30 of the first embodiment is assembled. The control unit 7 described in the first embodiment becomes a part for controlling the ion mobility analyzer of the second embodiment. In addition, when the ion generating device 30 is in positive ion mode, the ion mobility analyzer is also in positive ion mode, and when the ion generating device 30 is in negative ion mode, the ion mobility analyzer is also in negative ion mode. In addition, the ion mobility analyzer can be configured to be able to switch between positive ion mode and negative ion mode.

[0060] Figure 3 is a schematic cross-sectional view of an ion mobility analyzer in positive ion mode. Figure 4 1 is a schematic cross-sectional view of an ion mobility analyzer in negative ion mode. The ion mobility analyzer 40 of this embodiment includes an ion generating device 30, an ion detector 8, and electric field forming electrodes 10a to 10h (10). The ion detector 8 and the control unit 7 are configured to measure the current generated by the ion detector 8 receiving the charge from the ions and output the IMS spectrum. In addition, in the ion mobility analyzer 40, the gate 17 becomes the counter electrode 6.

[0061] The ion mobility analyzer 40 is a device for analyzing a sample gas by an ion mobility spectrometer (IMS). The ion mobility analyzer 40 includes: a reaction chamber 21 (between the electron emission element 2 and the grid 17 (counter electrode 6)) for ionizing the sample gas introduced into the housing 20 together with the carrier gas; and a drift region 22 (between the grid 17 and the ion collector electrode 9) for moving the ions (positive ions or negative ions) generated in the reaction chamber 21 toward the ion collector electrode 9 (ion detector 8) and separating them. The drift region 22 is a region where a potential gradient (electric field) is formed by a plurality of annular electric field forming electrodes 10a to 10h, and ions move from the grid 17 to the ion collector electrode 9 through the potential gradient. The reaction chamber 21 and the drift region 22 are separated by the grid 17 (grid electrode). In addition, at the end of the reaction chamber 21 opposite to the grid 17, the electron emission element 2 is arranged in such a manner that the surface electrode 5 is located on the reaction chamber 21 side. Therefore, the gate electrode 17 functions as the counter electrode 6 of the electron emitting element 2. In addition, the ion collector electrode 9 is arranged at the end of the drift region 22 opposite to the gate electrode 17.

[0062] When the sample gas enters the reaction chamber 21 together with the carrier gas from the sample inlet, the sample gas passes through the reaction chamber 21 between the electron emission element 2 and the grid 17, and is ionized by the charge caused by the electrons emitted from the electron emission element 2. The carrier gas and the unionized gas are discharged together with the drift gas through the exhaust port arranged on the side of the reaction chamber 21. In addition, the drift gas after removing impurities such as dry gas from the drift gas inlet on the side of the ion collector electrode 9 is introduced into the housing 20 of the ion mobility analysis device 40, so that the drift region 22 flows from the ion collector electrode 9 side to the grid 17 side, flows into the reaction chamber 21, and is discharged from the exhaust port together with the carrier gas. The drift gas is preferably dry nitrogen or air passed through a desiccant. In addition, in order to reduce impurities in the drift gas, it is preferred to pass through a filter before introducing the drift gas.

[0063] Since the configuration of the electron emitting element 2 has been described in the first embodiment, it is omitted here. When the ion generating device 30 and the ion mobility analyzing device 40 are in the positive ion mode, the control unit 7 (potential control circuit 13, power supply unit 12) applies a voltage to the lower electrode 3, the surface electrode 5 or the grid 17 so that the potential of the surface electrode 5 is higher than the potential of the lower electrode 3 and the potential of the grid 17. When the voltage is applied in this way, as described in the first embodiment, the positive ions X generated near the surface electrode 5 are + Towards the gate 17 and moves in the reaction chamber 21. Figure 3 As shown in FIG. 1 , since the sample gas Y is supplied to the reaction chamber 21, positive charges are generated from the positive ions X generated by the emitted electrons. + The sample gas Y is transferred to the sample gas, and the sample gas is positively ionized. Then, the positive ions Y of the sample gas are guided toward the grid 17 (counter electrode 6). + .

[0064] When the ion generating device 30 and the ion mobility analyzer 40 are in the negative ion mode, the control unit 7 (potential control circuit 13, power supply unit 12) applies voltage to the lower electrode 3, the surface electrode 5 or the grid 17 so that the potential of the surface electrode 5 is higher than the potential of the lower electrode 3 and the potential of the surface electrode 5 is lower than the potential of the grid 17. When the voltage is applied in this way, as described in the first embodiment, the negative ions X generated near the surface electrode 5 - Towards the gate 17 and moves in the reaction chamber 21. Figure 4 As shown in FIG. 1 , since the sample gas is supplied to the reaction chamber 21, the negative ions X generated by the emitted electrons are - Negative charges are transferred to the sample gas Y, and the sample gas is negatively ionized. Then, the negative ions Y of the sample gas are guided toward the grid 17 (counter electrode 6). - .

[0065] The gate 17 is an electrode that separates the reaction chamber 21 and the drift region 22, and is an electrode that controls the injection of positive ions or negative ions generated in the reaction chamber 21 into the drift region 22 by utilizing the electrostatic interaction between ions and the gate 17. In addition, the gate 17 also functions as a counter electrode 6 (sensing electrode). The gate 17 can be a ring electrode, a grid electrode, or an electrode in which a grid electrode is provided at the opening of the ring electrode. The gate 17 is preferably a grid electrode. The gate 17 can be arranged in a row together with a plurality of ring-shaped electric field forming electrodes 10a to 10h that form a potential gradient (electric field) in the drift region 22.

[0066] When the ion generating device 30 and the ion mobility analyzer 40 are in the positive ion mode, the control unit 7 (potential control circuit 13) applies voltage to the electric field forming electrodes 10a to 10h so that the potential of the drift region 22 gradually decreases as it approaches the ion collector 9. The positive ions that have passed through the gate 17 can move toward the ion collector electrode 9 in the drift region 22 by the electric field generated by the voltage application. For example, Figure 3 As shown, the potential of the ion collector electrode 9 can be set to 0V, the potential of the gate 17 (when open) can be set to +2500V, the potential of the surface electrode 5 can be set to +3000V, and the potential of the lower electrode 3 can be set to +2980V.

[0067] When the ion generating device 30 and the ion mobility analyzer 40 are in the negative ion mode, the control unit 7 (potential control circuit 13) applies voltage to the electric field forming electrodes 10a to 10h so that the potential of the drift region 22 gradually increases as it approaches the ion collector 9. The negative ions that have passed through the gate 17 can move the drift region 22 toward the ion collector electrode 9 by the electric field generated by the voltage application. For example, Figure 4 As shown, the potential of the ion collector electrode 9 can be set to 0V, the potential of the gate 17 (when open) can be set to -2500V, the potential of the surface electrode 5 can be set to -3000V, and the potential of the lower electrode 3 can be set to -3020V.

[0068] The gate 17 can be electrically connected to the control unit 7 (potential control circuit 13, power supply unit 12), and the control unit 7 controls the potential of the gate 17 to change the potential of the gate 17, thereby switching the open state and the closed state of the gate 17.

[0069] For example, when the potential of the gate 17 is low, the negative ions in the reaction chamber 21 cannot approach the gate 17 due to electrostatic interaction (negative ions have a force acting in the direction of repelling the gate 17), and cannot pass through the gate 17. In addition, when the potential of the gate 17 is low, the positive ions in the reaction chamber 21 move and contact the gate 17 in a manner attracted by the gate 17, so that the charge of the positive ions moves to the gate 17, and the positive ions are neutralized. Therefore, the positive ions cannot pass through the gate 17. Therefore, the gate 17 becomes closed (closed on the low potential side).

[0070] For example, when the potential of the gate 17 is high, the negative ions in the reaction chamber 21 move and contact in a manner attracted by the gate 17, whereby the charge of the negative ions moves toward the gate 17 and the negative ions are neutralized. Therefore, the negative ions cannot pass through the gate 13. In addition, when the potential of the gate 17 is high, the positive ions in the reaction chamber 21 cannot approach the gate 17 due to electrostatic interaction (positive ions have a force acting in the direction of repulsion from the gate 17) and cannot pass through the gate 17. Therefore, the gate 17 becomes closed (closed on the high potential side). For example, when the potential of the gate 17 is between closed on the low potential side and closed on the high potential side, the positive ions or negative ions in the reaction chamber 21 can pass through the gate 17, and the gate 17 becomes an open circuit.

[0071] If the control unit 7 (potential control circuit 13) is used to change the potential of the gate 17 so that the gate 17 is instantly changed from closed on the high potential side to open to closed on the low potential side, or from closed on the low potential side to open to closed on the high potential side, the gate 17 can be opened for only a very short time, and the negative ions or positive ions in the reaction chamber 21 can be injected into the drift region 22 only in this short time. Therefore, the negative ions or positive ions in the reaction chamber 21 can be injected into the drift region 22 in a single pulse.

[0072] The negative ions or positive ions injected into the drift region 22 through the gate 17 move the drift region 22 toward the ion collector 9 through the potential gradient formed by the electric field forming electrodes 10a to 10h, and reach the ion collector 9. Moreover, the negative ions or positive ions transfer charges to the ion collector 9 and become neutralized. In addition, the ion detector 8 (detection circuit 15) and the control unit 7 measure the current generated by the ion collector electrode 9 receiving the charge, and output it as an IMS spectrum. Specifically, the ion mobility spectrum (IMS spectrum) is obtained by plotting the flight time of the ions from the instant opening of the gate 17 to the arrival of the ions at the ion collector electrode 9 as the horizontal axis and the signal intensity (current, IMS intensity) as the vertical axis. When the ion mobility analyzer 40 is in the positive ion mode, the positive ions arrive at the ion collector electrode 9 and transfer the positive charge to the ion collector electrode 9. In addition, when the ion mobility analyzer 40 is in the negative ion mode, the negative ions arrive at the ion collector electrode 9 and transfer the negative charge to the ion collector electrode 9. Therefore, the direction of the current flowing through the detection circuit 15 is opposite in the positive ion mode and the negative ion mode. Therefore, when switching between the positive ion mode and the negative ion mode, the positive and negative polarities of the ion detector 8 (detection circuit 15) are switched.

[0073] The drift gas flowing from the ion collector electrode 9 to the gate 17 in the drift region 22 becomes a resistor for the positive or negative ions moving from the gate 17 to the ion collector electrode 9. The magnitude of this resistance (the mobility of the ions) varies depending on the type of ions. Generally speaking, the mobility is inversely proportional to the collision cross-sectional area of ​​the ions. Therefore, the larger the collision cross-sectional area of ​​the ions, the longer it takes for the ions to reach the ion collector electrode 9. Therefore, the time (movement time, peak position) from injection into the drift region 22 using the gate 17 to arrival at the ion collector electrode 9 varies depending on the type of ions. Therefore, the various ions injected from the gate 17 into the drift region 22 are separated during the movement in the drift region 22 and arrive at the ion collector electrode 9 with a time difference.

[0074] The IMS intensity (recovery current) of the IMS spectrum corresponds to the amount of ions that have reached the ion collector electrode 9, so peaks corresponding to various ions appear in the IMS spectrum. Moreover, the ions can be determined based on the peak position (movement time). In addition, by repeatedly measuring, the change in the amount of ions can be monitored. In addition, the peak intensity (peak height) or peak area of ​​the peak that appears in the IMS spectrum corresponds to the amount of ions. In addition, the peak of ions generated by air as a carrier gas also appears in the IMS spectrum. In addition, the control unit 7 can also accumulate and average multiple IMS spectra obtained by repeated measurements to calculate the average IMS spectrum (averaging processing). Thus, a stable IMS spectrum can be obtained. The number of averaged IMS spectra is not particularly limited, and is preferably greater than 10 and less than 200. For example, when the time required for one measurement is 0.1 seconds, the control unit 7 can average the IMS spectrum obtained by repeating 64 measurements and calculate the average IMS spectrum. In this case, the time required for the averaging process is 6.4 seconds.

[0075] After the sample gas is introduced into the reaction chamber 21, it is measured in the positive ion mode and the negative ion mode, respectively, so that for one sample, both the IMS spectrum in the positive ion mode and the IMS spectrum in the negative ion mode can be obtained. Therefore, by switching between the positive ion mode and the negative ion mode to perform analysis in two modes, the analysis accuracy of the sample gas can be improved.

[0076] The control unit 7 can be configured to change the potential of the surface electrode 5 to a potential with opposite polarity and substantially equal absolute value, and change the potential of the lower electrode 3 to a potential with opposite polarity and different absolute value when switching between the negative ion mode and the positive ion mode. Thus, the negative ion mode and the positive ion mode can be switched while the potential of the ion collector 9 is maintained at 0V. In addition, by changing the potential of the lower electrode 3 to a potential with opposite polarity and different absolute value, it is possible to suppress the electrons from being emitted from the electron emission element 2. In addition, when switching between the negative ion mode and the positive ion mode, the control unit 7 can change the potential of the lower electrode 3 and the potential of the surface electrode 5 so that the potential of the lower electrode 3 is lower than the potential of the surface electrode 5. Therefore, the absolute value of the potential of the lower electrode 3 in the negative ion mode is greater than the absolute value of the potential of the lower electrode 3 in the positive ion mode. For example, in the negative ion mode, when the potential difference between the lower electrode 3 and the surface electrode 5 is 15V and the potential of the surface electrode 5 is -3000V, the potential of the lower electrode 3 can be made -3015V. For example, when the potential difference between the lower electrode 3 and the surface electrode 5 in the positive ion mode is 30V and the potential of the surface electrode 5 is +3000V, the potential of the lower electrode 3 can be made +2970V.

[0077] In addition, in the positive ion mode, if it is an electron with energy above the ionization energy of air, the type of air ions remains unchanged. Therefore, if the 20V at which positive ions are detected is increased to 60V at which the element is damaged, the sensitivity and resolution can be improved by adjusting the element driving voltage. By increasing the element driving voltage, the amount of positive ions increases, and the sensitivity can be improved. On the other hand, by reducing the element driving voltage, the peak width becomes thinner, and the resolution can be improved. When adjusting the element driving voltage, the potential of the lower electrode 3 can be changed without changing the potential of the surface electrode 5. Thus, the potential difference between the surface electrode 5 and the grid 17 (opposing electrode 6) can be maintained. In the case where the control unit 7 is set in a manner that the average IMS spectrum is calculated by accumulating and averaging a plurality of IMS spectra obtained by repeated measurements, the control unit 7 can be set to switch between the negative ion mode and the positive ion mode each time the calculation of the average IMS spectrum is completed. Thus, both negative ions and positive ions generated from the components contained in the sample gas can be detected. For example, when the time required for one measurement is 0.1 seconds, the control unit 7 can average the IMS spectra obtained by repeating the measurement in the negative ion mode 64 times to calculate the average IMS spectrum. Thereafter, the control unit 7 switches the measurement mode from the negative ion mode to the positive ion mode, and averages the IMS spectra obtained by repeating the measurement in the positive ion mode 64 times to calculate the average IMS spectrum.

[0078] The control unit 7 (potential control circuit 13, power supply unit 12) can be configured to adjust the voltage applied between the lower electrode 3 and the surface electrode 5 so that the reference peak (e.g., the main peak of air ions) appearing in the IMS spectrum is a predetermined height or a predetermined area. Thus, the sample gas can be quantitatively analyzed based on the peak area or peak height of the IMS spectrum.

[0079] The control unit 7 (potential control circuit 13, power supply unit 12) can also be configured to adjust the voltage applied between the lower electrode 3 and the surface electrode 5 so that the height or area of ​​the first reference peak (e.g., the main peak of air ions) appearing in the IMS spectrum in the positive ion mode is substantially the same as the height or area of ​​the second reference peak (e.g., the main peak of air ions) appearing in the IMS spectrum in the negative ion mode. Thus, it is possible to use the peaks appearing in the IMS spectrum in the positive ion mode and the peaks appearing in the IMS spectrum in the negative ion mode to perform qualitative analysis and quantitative analysis. In addition, the description of the ion generating device of the first embodiment is also applicable to the ion generating device included in the ion mobility analysis device of the second embodiment as long as there is no contradiction.

[0080] Third embodiment

[0081] The third embodiment relates to a field asymmetric ion mobility analyzer (analyzer that performs analysis by field asymmetric IMS (FAIMS)) assembled with the ion generating device 30 of the first embodiment. The control unit 7 described in the first embodiment becomes a part for controlling the ion mobility analyzer of the third embodiment. In addition, when the ion generating device 30 is in positive ion mode, the ion mobility analyzer is also in positive ion mode, and when the ion generating device 30 is in negative ion mode, the ion mobility analyzer is also in negative ion mode. In addition, the ion mobility analyzer can be configured to be able to switch between positive ion mode and negative ion mode.

[0082] Figure 5 is a schematic cross-sectional view of an ion mobility analyzer in positive ion mode. Figure 6 2 is a schematic cross-sectional view of an ion mobility analyzer in a negative ion mode. Figure 5 As with two ion collector electrodes 9a, 9b, it is also possible to Figure 6 The ion mobility analyzer 40 of this embodiment includes an ion generating device 30, an ion detector 8, and electric field forming electrodes 10a and 10b. The ion detector 8 and the control unit 7 are configured to measure the current generated by the ion detector 8 receiving the charge from the ions and output the IMS spectrum.

[0083] In the ion mobility analysis device 40 of the present embodiment, the sample gas contained in the carrier gas is ionized by using the ion generator 30 described in the first embodiment in the reaction chamber 21, and the ions are caused to flow through the field asymmetric ion moving section 25 (the region between the electric field forming electrode 10a and the electric field forming electrode 10b) between the parallel plate electrodes together with the carrier gas. Then, the negative ions or positive ions moved by the field asymmetric ion moving section 25 through the ion collector electrodes 9a, 9b, 9 (ion detector 8) arranged on the downstream side of the field asymmetric ion moving section 25 are detected.

[0084] Clean dry air is preferably used as the carrier gas. The sample gas and the carrier gas introduced from the sample inlet enter the reaction chamber 21. The reaction chamber 21 is a region between the surface electrode 5 and the counter electrode 6 of the electron emission element 2. The electron emission element 2 can be arranged on the inner wall of the housing 20, and the counter electrode 6 can be arranged on the inner wall opposite to the inner wall on which the electron emission element 2 is arranged. In addition, the counter electrode 6 is arranged in a manner opposite to the surface electrode 5 of the electron emission element 2. Since the configuration of the electron emission element 2 has been described in the first embodiment, it is omitted here.

[0085] When the ion generating device 30 and the ion mobility analyzer 40 are in the positive ion mode, the control unit 7 (potential control circuit 13, power supply unit 12) applies a voltage to the lower electrode 3, the surface electrode 5 or the counter electrode 6 so that the potential of the surface electrode 5 is higher than the potential of the lower electrode 3 and the potential of the counter electrode 6. When the voltage is applied in this way, as described in the first embodiment, the positive ions X generated near the surface electrode 5 are + The sample gas Y moves toward the counter electrode 6 and moves in the reaction chamber 21. In addition, since the sample gas Y is supplied to the reaction chamber 21 together with the carrier gas, Figure 5 In this way, positive charges are generated from positive ions X generated by the emitted electrons. + The sample gas Y is transferred to the sample gas, and the sample gas is positively ionized. Then, the positive ions Y of the sample gas + The positive ions Y of the sample gas may flow to the field asymmetric ion moving section 25 together with the carrier gas. + Move to the field asymmetric ion moving unit 25 .

[0086] When the ion generating device 30 and the ion mobility analyzer 40 are in the negative ion mode, the control unit 7 (potential control circuit 13, power supply unit 12) applies voltage to the lower electrode 3, the surface electrode 5 or the counter electrode 6 so that the potential of the surface electrode 5 is higher than the potential of the lower electrode 3 and the potential of the surface electrode 5 is lower than the potential of the counter electrode 6. When the voltage is applied in this way, as described in the first embodiment, the negative ions X generated near the surface electrode 5 - The sample gas is supplied to the reaction chamber 21, so that Figure 6 In this way, negative charges are generated from negative ions X generated by emitting electrons. - The sample gas is transferred to the sample gas Y, and the sample gas is negatively ionized. Then, the negative ions Y of the sample gas - The negative ions Y of the sample gas may flow to the field asymmetric ion moving section 25 together with the carrier gas. - Move to the field asymmetric ion moving unit 25 .

[0087] The field asymmetric ion moving part 25 is a region between the electric field forming electrode 10a and the electric field forming electrode 10b. The electric field forming electrode 10a can be arranged on the inner wall of the housing 20, and the electric field forming electrode 10b can be arranged on the inner wall opposite to the inner wall where the electric field forming electrode 10a is arranged. In addition, the electric field forming electrode 10b can be arranged opposite to the electric field forming electrode 10a.

[0088] The ions of the sample gas moving from the reaction chamber 21 to the field asymmetric ion moving part 25 swing as the electric field generated by applying a dispersion voltage (asymmetric high-frequency voltage) to the electric field forming electrodes 10a and 10b changes, and the direction of travel changes. In addition, the value of the ion mobility of the sample gas changes depending on the electric field strength. The separation of ions in FAIMS is based on the change of ion mobility under high electric field strength.

[0089] The time average of the dispersion voltage within one cycle of the waveform is 0. In addition, the voltage between the electrodes is about ± thousands of V (± 100 ~ ± 2000 V), the electric field strength is ± tens of thousands of V / cm (about ± 5000 ~ ± 40000 V / cm), and the frequency is hundreds of KHz to several MHz (100kHz ~ 3MHz). In addition, by applying a dispersion voltage and a compensation voltage (CV) between the electric field forming electrodes 10a, 10b, the ion mobility changes and the direction of travel changes. Therefore, by scanning the compensation voltage (CV) over time, the type of ions that can reach the ion collector electrodes 9, 9a, 9b changes (the ions that have reached the electric field forming electrodes 10a, 10b are neutralized). Therefore, by measuring the IMS intensity (recovery current) using the ion detector 8, an IMS spectrum can be obtained. In this way, ions can be separated and detected.

[0090] The compensation voltage (DC voltage) is in the range of about ±100V, and the electric field strength is in the range of ±2000V / cm. The interval between the electric field forming electrode 10a and the electric field forming electrode 10b is from tens of μm to several mm (0.01 to 2 mm), and the length of the electric field forming electrodes 10a and 10b (the length of the field asymmetric ion moving part 25) is from hundreds of μm to tens of mm (0.1 to 30 mm). The ions reaching the electric field forming electrodes 10a and 10b are neutralized. The neutralized substances are exhausted together with the carrier gas, or stored in the electric field forming electrodes 10a, 10b or the ion collector electrode 9. In order to remove the stored substances, it can be removed by flowing a gas (clean dry air, etc.) that does not contain the sample gas from the sample inlet and the carrier gas inlet. In addition, the flowing gas can be at a high temperature. The ions that can pass through the field asymmetric ion moving part 25 are detected by the ion detector 8, and the neutral substances and the carrier gas are discharged from the exhaust port.

[0091] In the negative ion mode, the voltage applied between the lower electrode 3 and the surface electrode 5 of the electron emitting element 2 can be set to 10V to 18V, and the polarity of the counter electrode 6 and the ion detector 8 is set to positive, so that substances that are easily negatively ionized can be measured. In the positive ion mode, the voltage applied between the lower electrode 3 and the surface electrode 5 of the electron emitting element 2 can be set to 18V to 50V, and the polarity of the counter electrode 6 and the ion detector 8 is set to negative, so that substances that are easily positively ionized can be measured. The ion mobility analysis device 40 can also switch between the negative ion mode and the positive ion mode to analyze the same sample gas in both modes. As a result, for one sample gas, both the IMS spectrum in the negative ion mode and the IMS spectrum in the positive ion mode can be obtained, which can improve the analysis accuracy.

[0092] like Figure 5 When the ion detector 8 has an ion collector electrode 9a for detecting negative ions and an ion collector electrode 9b for detecting positive ions, as in the ion mobility analysis device 40 shown in FIG. 1 , the polarity of the ion detector 8 does not need to be reversed even when switching between the negative ion mode and the positive ion mode. Figure 6 As shown in the ion mobility analysis device 40, when the ion detector 8 has only one ion collector electrode 9, if the negative ion mode and the positive ion mode are switched, the polarity of the ion detector 8 is reversed. Thus, the control unit 7 can output the IMS spectrum in the negative ion mode and the IMS spectrum in the positive ion mode. In this way, by setting the ion collector electrode 9 to only one, the ion mobility analysis device can be miniaturized. The description of the ion generating device of the first embodiment is also applicable to the ion generating device included in the ion mobility analysis device of the third embodiment as long as there is no contradiction. In addition, the description of the second embodiment is also applicable to the third embodiment as long as there is no contradiction.

[0093] Positive ion detection experiment

[0094] 3 g of silicone resin and 0.039 g (1.3%) of Ag nanoparticles were stirred with an ultrasonic vibrator to prepare a coating liquid. The coating liquid was applied to the MAM (molybdenum, aluminum, molybdenum) electrode (lower electrode) on the glass substrate by spin coating to form an intermediate layer with a thickness of 1.0 μm. A gold electrode (surface electrode) with a thickness of 20 nm was formed on the intermediate layer by sputtering. The electron emission element thus prepared was mounted on a Figure 3 , Figure 4 Analysis based on ion mobility spectrometry (IMS) was performed in positive ion mode on the drift tube ion mobility analyzer shown.

[0095] In the analysis, the carrier gas was set to humidified air (humidity: 44%), and the drift gas was set to dry air. In addition, the sample gas was not supplied to the analysis device, that is, only the carrier gas was supplied to the analysis device. In addition, the potential of the ion collector electrode was set to 0V, the potential of the surface electrode was set to +3000V, and the potential of the lower electrode was set to +2981V (element driving voltage: 19V), +2980V (element driving voltage: 20V) or +2972V (element driving voltage: 28V). In addition, the potential of the aperture grid 18 was +163V.

[0096] Figure 7 This is an IMS spectrum obtained by analyzing the device with a drive voltage of 28V. Figure 8 This is an IMS spectrum obtained by analyzing the device with the drive voltage set to 19V and 20V. Figure 7 As shown in the IMS spectrum of , it was confirmed that the peak of positive ions generated from humidified air appeared in the IMS spectrum in the positive ion mode. Figure 8 As shown, in the IMS spectrum when the element driving voltage is set to 19V, no peak appears, but when the element driving voltage is set to 20V, a peak appears in the IMS spectrum. Therefore, the following is confirmed: in the case where the carrier gas is set to humidified air in the positive ion mode, by applying a voltage of 20V or more between the lower electrode and the surface electrode, positive ions can be generated, thereby enabling analysis. It is believed that the voltage varies depending on the composition of the electron emission element (such as the thickness of the intermediate layer), etc. In addition, in the case where the carrier gas is set to dry air in the positive ion mode, the peak of the IMS spectrum appears from the element driving voltage of 28V.

[0097] Next, analysis was performed using an ion mobility spectrometer (IMS) in positive ion mode, with dry air as the carrier gas and the element drive voltage set to 55 V (lower electrode potential: +2945 V) or 60 V (lower electrode potential: +2940 V). Other analysis conditions were the same as those in the above analysis. Fig. 9 The IMS spectrum obtained by analysis is shown. In the IMS spectrum with the element drive voltage set to 55V, a large peak of positive ions generated from humidified air appears. If the element drive voltage is set to 60V, the IMS intensity of the peak appearing in the IMS spectrum decreases sharply. It is believed that the reduction in peak intensity is caused by damage to the electron emission element. Therefore, in the electron emission element made in this experiment, the upper limit of the element drive voltage is about 60V. However, it is believed that this voltage varies depending on the composition of the electron emission element, etc.

[0098] Negative ion detection experiment

[0099] The analysis device used in the positive ion detection experiment was set to negative ion mode and an analysis based on an ion mobility spectrometer (IMS) was performed. In the analysis, the carrier gas was set to humidified air (humidity: 44%), and the drift gas was set to dry air. In addition, the sample gas was not supplied to the analysis device, that is, only the carrier gas was supplied to the analysis device. In addition, the potential of the ion collector electrode was set to 0V, the potential of the surface electrode was set to -3000V, and the potential of the lower electrode was set to -3009V (element driving voltage: 9V), -3010V (element driving voltage: 10V), -3010.5V (element driving voltage: 10.5V), -3011V (element driving voltage: 11V), -3011.2V (element driving voltage: 11.2V) or -3011.5V (element driving voltage: 11.5V), -3013V (element driving voltage: 11.5V), The potential of the aperture grid 18 is -163V.

[0100] Fig.10 This is an IMS spectrum obtained by analyzing the device with a drive voltage of 13V. Fig.11 This is an IMS spectrum obtained by analysis with the device driving voltage set to 9V to 11.5V. Fig.12 This is an IMS spectrum obtained by analyzing the device driving voltage at 14.5V to 18V. Fig.10 As shown in the IMS spectrum of FIG. 1 , it was confirmed that the peak of negative ions generated from the humidified air appeared in the IMS spectrum in the negative ion mode. Fig.11 As shown in the figure, if the element driving voltage is set to 9V, a peak appears in the IMS spectrum, and when the element driving voltage increases, the IMS intensity of the peak gradually increases. Therefore, the following is confirmed: when the carrier gas is set to humidified air in the negative ion mode, by applying a voltage of 9V or more between the lower electrode and the surface electrode, negative ions can be generated, thereby enabling analysis. It is believed that this voltage varies depending on the composition of the electron emission element (for example, the thickness of the intermediate layer), etc. In addition, as Fig.12 As shown in the IMS spectrum of FIG. 1 , in addition to the main peak at about 9.3 milliseconds, a peak appears at about 8.8 milliseconds, and this peak gradually increases when the element driving voltage becomes 15V or more.

[0101] Ethanol analysis experiment

[0102] The analysis device used in the positive ion detection experiment was set to positive ion mode, and ethanol (sample gas) was analyzed. In the analysis, the sample gas was 0.3 ppm ethanol, the carrier gas was humidified air (humidity: 44%), and the drift gas was dry air. In addition, the potential of the ion collector electrode was set to 0 V, the potential of the surface electrode was set to +3000 V, and the potential of the lower electrode was set to +2962 V (element driving voltage: 38 V). The obtained IMS spectrum is shown in Fig.13 In this IMS spectrum, the peak at 11.1 milliseconds is considered to be the peak of ethanol, and the peak at 12.2 milliseconds is considered to be the peak of ethanol dimer. The peak at 10.6 milliseconds is the peak of humidified air. Thus, it was confirmed that the sample gas can be analyzed in the positive ion mode.

[0103] Description of Reference Numerals

[0104] 2: electron emission element; 3: lower electrode; 4: middle layer; 5: surface electrode; 6: opposite electrode; 7: control unit; 8: ion detector; 9, 9a, 9b: ion collectors; 10, 10a~10h: electrodes for forming electric field; 12: power supply unit; 13: potential control circuit; 15: detection circuit; 17: grid; 18: aperture grid; 20: shell; 21: reaction chamber; 22: drift region; 30: ion generation device; 40: ion mobility analysis device.

Claims

1. An ion generating device, characterized in that: It comprises: an electron emitting element, an opposing electrode and a control unit. The electron emission element includes: a lower electrode; a surface electrode; and an intermediate layer disposed between the lower electrode and the surface electrode. The counter electrode is arranged to face the surface electrode. The control unit is configured to: apply a voltage to the surface electrode, the lower electrode or the counter electrode so that in a positive ion mode for generating positive ions, the potential of the surface electrode is higher than the potential of the lower electrode and the potential of the counter electrode; The control unit is configured to apply a voltage between the lower electrode and the surface electrode so that electrons with energy higher than ionization energy of a gas component between the surface electrode and the counter electrode are emitted from the electron emitting element in the positive ion mode.

2. The ion generating device according to claim 1, characterized in that The control unit applies a voltage of 16 V or more and 60 V or less between the lower electrode and the surface electrode in the positive ion mode.

3. The ion generating device according to claim 1 or 2, characterized in that: The control unit is configured to apply a voltage to the surface electrode, the lower electrode or the opposing electrode, so that in a negative ion mode for generating negative ions, the potential of the surface electrode is higher than the potential of the lower electrode and lower than the potential of the opposing electrode, and the control unit is configured to be able to switch between the negative ion mode and the positive ion mode.

4. The ion generating device according to claim 3, characterized in that The control unit applies a voltage of 6 V or more and 60 V or less between the lower electrode and the surface electrode in the negative ion mode.

5. The ion generating device according to claim 3, characterized in that When switching between the negative ion mode and the positive ion mode, the control unit switches so that the potential difference between the surface electrode and the lower electrode in the positive ion mode is greater than the potential difference between the surface electrode and the lower electrode in the negative ion mode.

6. An ion mobility analysis device, characterized in that: It has: The ion generating device according to any one of claims 1 to 5; an ion detector; and Electrodes for forming an electric field, The ion detector and the control unit are configured to measure a current generated by the ion detector receiving electric charges from ions and output an IMS spectrum.

7. The ion mobility analysis device according to claim 6, characterized in that: The control unit is configured to adjust the voltage applied between the lower electrode and the surface electrode so that a reference peak appearing in the IMS spectrum has a predetermined height or a predetermined area.

8. The ion mobility analysis device according to claim 6, characterized in that: The control unit is configured to adjust a voltage applied between the lower electrode and the surface electrode by fixing the potential of the surface electrode and changing the potential of the lower electrode.

9. The ion mobility analysis device according to claim 6, characterized in that: The control unit is configured to apply a voltage to the surface electrode, the lower electrode or the counter electrode, so that in a negative ion mode for generating negative ions, the potential of the surface electrode is higher than the potential of the lower electrode and lower than the potential of the counter electrode, and the control unit is configured to be able to switch between the negative ion mode and the positive ion mode, The control unit is configured to adjust the voltage applied between the lower electrode and the surface electrode so that the height or area of ​​the first reference peak appearing in the IMS spectrum in the positive ion mode is substantially the same as the height or area of ​​the second reference peak appearing in the IMS spectrum in the negative ion mode.

10. The ion mobility analysis device according to claim 6, characterized in that: The control unit is configured to apply a voltage to the surface electrode, the lower electrode or the counter electrode so that in a negative ion mode for generating negative ions, the potential of the surface electrode is higher than the potential of the lower electrode and lower than the potential of the counter electrode, and the control unit is configured to be able to switch between the negative ion mode and the positive ion mode. The control unit is configured to change the potential of the surface electrode to a potential with opposite polarity and substantially equal absolute value, and change the potential of the lower electrode to a potential with opposite polarity and different absolute value when switching between the negative ion mode and the positive ion mode.

11. The ion mobility analysis device according to any one of claims 6 to 10, characterized in that: The control unit is configured to apply a voltage to the surface electrode, the lower electrode or the counter electrode, so that in a negative ion mode for generating negative ions, the potential of the surface electrode is higher than the potential of the lower electrode and lower than the potential of the counter electrode, and the control unit is configured to be able to switch between the negative ion mode and the positive ion mode, The control unit is configured to calculate an average IMS spectrum by cumulatively averaging a plurality of IMS spectra obtained by repeated measurement, and to switch between the negative ion mode and the positive ion mode every time calculation of the average IMS spectrum is completed.

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