JP6108387B2 - Analyzer using ionic liquid beam - Google Patents

Description

The present invention relates to an analysis apparatus for analyzing electrons and ions generated by carrying an analysis sample into a vacuum and irradiating the analysis sample with an electron beam, a laser, or an ion beam.
The analysis method using electron beam irradiation relates to a scanning electron microscope (hereinafter referred to as SEM) and a transmission electron microscope (hereinafter referred to as TEM).
An analysis technique using laser irradiation relates to a matrix-assisted laser desorption / ionization method (hereinafter referred to as MALDI).
An analysis method using ion beam irradiation relates to secondary ion mass spectrometry (hereinafter referred to as SIMS).

An electron microscope (SEM, TEM, etc.) is a technique for measuring the shape of an analysis sample by irradiating an analysis sample with an electron beam and detecting generated secondary electrons, transmission electrons, and the like. Analytical samples include those that have conductivity and those that do not have conductivity. If the analysis sample has conductivity and is grounded, no charge-up occurs even when the electron beam is irradiated. On the other hand, if the analysis sample is an object made of an insulator or an object surrounded by an insulator, charge-up occurs when the electron beam is irradiated, so it is difficult to accurately observe the sample image. There are challenges.
As one method for solving this problem, a method is known in which carbon, aluminum, platinum, or the like is vapor-deposited on the sample surface to release the charged charges on the sample surface and prevent charge-up.
Patent Document 1 proposes preventing charge-up by impregnating an analysis sample with an ionic liquid or applying an ionic liquid to the surface of the analysis sample. This technique is also advantageous in that it can suppress deformation due to drying, which is a problem in biological samples containing water, and can observe a shape close to a living state.

MALDI, which is an effective technique for mass spectrometry, is a technique for irradiating an analysis sample with a laser and measuring the mass-to-charge ratio (m / z) of the generated ions. By absorbing the laser efficiently and preliminarily mixing with the analysis sample using a substance that is easily ionized as a matrix, it becomes possible to detect a molecule having a large molecular weight with high sensitivity without breaking it as much as possible. Patent Document 2 proposes to use an ionic liquid as a matrix in MALDI.
SIMS, which is a powerful method for surface analysis, irradiates the analysis sample with a primary ion beam, and performs mass analysis of secondary ions emitted from the analysis sample surface, thereby providing information on the atomic and molecular structure of the analysis sample. It is an analysis technique aiming at obtaining.
Patent Document 3 proposes a method of wrapping, that is, coating, an analysis sample for SIMS with an ionic liquid in order to prevent charge-up or drying of the analysis sample.
Further, Non-Patent Document 1 reports the usefulness of increasing the secondary ion intensity by using an ionic liquid as a matrix in SIMS analysis (Matrix-Enhanced Secondary Ion Mass Spectrometry: ME-SIMS). be called).
That is, coating the analysis sample with the ionic liquid not only prevents charge-up and drying, but also increases the secondary ion intensity, and can be said to be a very effective technique in SIMS analysis.
In addition, an ionic liquid (Ionic Liquid) is a substance also called a room temperature molten salt, and is a general term for salts that are in a liquid state even at room temperature. An ionic liquid is composed of a cation and an anion, and since it has a melting point lower than room temperature, it is a liquid at room temperature. It has high conductivity and has almost no vapor pressure. It is a substance having characteristics such as being stable (see Patent Documents 3 and 4).

International Publication WO2007 / 083756 International Publication WO 2004/023147 JP 2009-128045 A Japanese Unexamined Patent Publication No. 2011-10052

J. et al. J. et al. D. Fitzgerald, P.M. Kunnath, and A.A. V. Walker, “Matrix-Enhanced Secondary Ion Mass Spectrometry (ME SIMS) Using Room Temperature Ionic Liquid Matrix” (Analytical Chemistry 44, 19).

As described above, pretreatment such as impregnation of an ionic liquid on an analysis sample or coating may be performed, but these treatments are performed before analysis. Since analysis such as SEM, MALDI, or SIMS is performed in a vacuum, pretreatment such as coating of an ionic liquid is completed before introducing an analysis sample into the vacuum container.
On the other hand, in SEM, TEM, etc., when the analysis time is long and the temperature of the sample surface is increased by electron beam irradiation, there is a concern that the ionic liquid on the surface of the analysis sample evaporates and disappears.
In the case of irradiation with a laser or ion beam, the sample surface is scattered in a vacuum by sputtering or the like, so that the ionic liquid on the sample surface gradually disappears as the analysis proceeds.
That is, it is inevitable that the amount of ionic liquid on the surface of the analysis sample decreases with the passage of analysis time, with the peak at the start of analysis. Decreasing the ionic liquid leads to a reduction in prevention effects such as charge-up and drying, and means that stable measurement cannot be performed gradually.
In particular, since SIMS uses sputtering by ion beam irradiation, the ionic liquid is eliminated by sputtering, despite the fact that analysis from the sample surface to the depth direction inside the sample is also possible. Therefore, analysis of the inside of the sample becomes difficult unless an ionic liquid is additionally supplied by some method.
In addition, as in SIMS and MALDI, when the ionic liquid has an effect as a matrix and has an effect of increasing the ionization efficiency, the ionization efficiency also varies when the coating amount of the ionic liquid varies. , Which leads to the problem that the quantitativeness deteriorates. Therefore, for highly accurate analysis, it is necessary to keep the coating amount of the ionic liquid constant from the start to the end of the analysis.
As one solution, it is conceivable that after a certain amount of analysis is performed, the analysis is once stopped, the analysis sample is taken out from the vacuum container into the atmosphere, and the ionic liquid is coated again. However, this method has a serious problem that the analysis process becomes complicated, but it takes a long time to evacuate from atmospheric pressure to a high vacuum condition again.

  In order to solve the above problems, in the present invention, an ionic liquid is appropriately applied to the surface of an analysis sample by irradiating the analysis sample in the vacuum vessel as many times as necessary or continuously with an ionic liquid beam. The coating effect of the ionic liquid (suppression of charge-up, suppression of deformation due to drying, increase of secondary ions) and the like can be maintained from the start to the end of analysis. The ionic liquid beam can be generated by a method of electrospraying an ionic liquid in a vacuum.

That is, the analysis apparatus of the present invention is an apparatus that irradiates an analysis sample with an electron beam, a laser, or an ion beam and analyzes electrons, ions, etc. emitted from the analysis sample, and irradiates the ionic liquid beam. The ionic liquid beam source analyzes the coating amount of the ionic liquid by irradiating the ionic liquid beam to the analytical sample placed in a vacuum, supplying the ionic liquid to the surface of the analytical sample, and coating it. It is characterized in that it can be held stably from the start to the end of analysis.
The present invention is also characterized in that, in the analysis apparatus, the ionic liquid beam source is based on electrospray of an ionic liquid in a vacuum.
In the analyzer according to the present invention, the ionic liquid beam source has a deceleration part in the middle of transport of the ionic liquid beam generated by electrospray, and the mass-to-charge ratio m / z mixed in the beam is small. The components are separated and removed from the beam.
Further, the present invention is characterized in that in the analyzer, the mass of secondary ions is analyzed using the ionic liquid beam source also as a primary ion beam source.
According to the present invention, in the analyzer, the deceleration unit is configured by a deceleration electrode, and a component having a small mass-to-charge ratio m / z mixed in the beam is decelerated by adjusting a voltage applied to the deceleration electrode. It is characterized in that the analysis sample is irradiated with a beam consisting only of a component having a large mass-to-charge ratio m / z while being prevented from passing through the electrode, and the mass of secondary ions is analyzed.
Further, the present invention provides the analyzer with acceleration voltage control means for controlling an acceleration voltage of the ionic liquid beam, and supplies the ionic liquid to the surface of the analysis sample by adjusting the acceleration voltage by the acceleration voltage control means. The mass of the secondary ions is analyzed while appropriately switching between the coating mode for coating and the analysis mode for generating secondary ions from the surface of the analysis sample.

The analyzer according to the present invention makes it possible to replenish the ionic liquid lost from the surface of the analysis sample by electron beam irradiation, laser irradiation, or ion beam irradiation in the vacuum inside the analyzer, and the coating effect (charge up) of the ionic liquid. And effects such as prevention of drying or increase in ionic strength) can be stably maintained from the start of analysis to the end of analysis.
In addition, according to the present invention, switching between the coating mode and the analysis mode can be performed by controlling the acceleration voltage, whereby the amount of ionic liquid on the surface of the analysis sample can be controlled within a predetermined range from the start to the end of the analysis. , Stable measurement becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows Example 1 of this invention, Comprising: The schematic of the electron microscope provided with the ionic liquid beam source which can supply an ionic liquid as a beam with respect to the analysis sample surface installed in the vacuum. It is a figure which shows Example 2 of this invention. It is a figure which shows Example 3 of this invention. It is a figure which shows Example 4 of this invention. It is a figure which shows Example 5 of this invention. The conceptual diagram of the experimental apparatus used in order to verify the effect of the deceleration electrode of Example 5. FIG. An example of the transient response experiment result measured using the experimental apparatus of FIG. It is the figure which put together the result of FIG. It is a figure which shows Example 6 of this invention. The conceptual diagram of the SIMS experimental apparatus used in order to verify Example 6. FIG. The 1st example of the mass spectrum of the secondary ion measured with the SIMS experimental apparatus of FIG. The 2nd example of the mass spectrum of the secondary ion measured with the SIMS experimental apparatus of FIG. It is a figure which shows Example 7 of this invention. It is a figure which shows Example 8 of this invention, Comprising: It is the figure explaining switching the coating mode and analysis mode suitably by adjusting the acceleration voltage of an ionic liquid beam.

  Hereinafter, a configuration of an analyzer having an ionic liquid coating mechanism for an analysis sample by ionic liquid beam irradiation according to an embodiment of the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a schematic diagram of a first embodiment of the present invention. Basically, it is a general electron microscope (SEM or the like), but is characterized by having an ionic liquid beam source used for supplying an ionic liquid to an analysis sample installed in a vacuum. By irradiating an ionic liquid beam from an ionic liquid beam source, an ionic liquid can be supplied to the surface of an analysis sample installed in a vacuum.
Even if the ionic liquid tends to disappear from the surface of the analysis sample due to evaporation or the like due to electron beam irradiation, the ionic liquid can be supplied as a beam from the ionic liquid beam source. Can be balanced. The ionic liquid beam may be irradiated intermittently or may be irradiated continuously simultaneously with the electron beam irradiation.
Since the disappearance and supply of the amount of the ionic liquid on the surface of the analysis sample are balanced, the problem of charge-up and the deformation of the sample due to drying do not occur, so that stable measurement can be performed from the start of analysis to the end of analysis.

(Example 2)
FIG. 2 is a schematic diagram of a second embodiment of the present invention. Basically, it is a general MALDI mass spectrometer, but is characterized by having an ionic liquid beam source used for supplying an ionic liquid to an analysis sample installed in a vacuum. By irradiating an ionic liquid beam from an ionic liquid beam source, an ionic liquid can be supplied to the surface of an analysis sample installed in a vacuum.
Even if the ionic liquid scatters and disappears from the analysis sample due to laser irradiation, the ionic liquid can be supplied as a beam from the ionic liquid beam source, so that the ionic liquid is not lost from the analysis sample. The ionic liquid beam may be irradiated intermittently or continuously.

(Example 3)
FIG. 3 is a schematic diagram of a third embodiment of the present invention. Basically, it is a general SIMS apparatus, but is characterized in that it includes an ionic liquid beam source used for supplying an ionic liquid to an analysis sample installed in a vacuum. By irradiating an ionic liquid beam from an ionic liquid beam source, an ionic liquid can be supplied to the surface of an analysis sample installed in a vacuum.
Even if the ionic liquid tends to disappear from the surface of the analysis sample by sputtering due to the primary ion beam irradiation, the ionic liquid can be supplied as a beam from the ionic liquid beam source. Can be balanced. The ionic liquid beam may be irradiated intermittently, or may be irradiated continuously simultaneously with the primary ion beam.
This balances the disappearance and supply of the amount of ionic liquid on the surface of the analysis sample, so there is no charge-up problem or deformation of the sample due to drying, and the effect of increasing secondary ions can be made constant. Stable measurement from the end of the analysis to the end of the analysis.

Example 4
FIG. 4 is a schematic diagram of Embodiment 4 of the present invention. The basic configuration is the same as that of the third embodiment shown in FIG. 3 except that an ionic liquid beam source based on a method of electrospraying an ionic liquid in a vacuum is mounted.
The electrospray section is composed of a thin metal tube (capillary), a counter electrode, an ionic liquid supply line not shown in the figure, a high-voltage power supply, and the like. The ionic liquid is supplied from the ionic liquid supply line to the inside of the metal thin tube, and electrospray is performed toward the counter electrode installed in front of the metal thin tube. A high voltage power source is used to control the potential of the metal thin tube and the counter electrode. When the potential of the metal thin tube is higher than that of the counter electrode, a positively charged ionic liquid beam can be generated. On the contrary, when the potential of the metal thin tube is set lower than that of the counter electrode, a negatively charged ion beam can be generated. Since the ionic liquid has a very low vapor pressure and high conductivity, it can be stably electrosprayed without any problem even in a high vacuum.
The inner diameter of the metal thin tube is about 5 μm to 100 μm. The gap length between the tip of the thin metal tube and the counter electrode is about several millimeters, and electrospray occurs when a potential difference of about 1 kV to 3 kV occurs. The metal thin tube can be substituted with a conductive material such as an insulating thin tube made of glass. There is an electrode hole (aperture) in the center of the counter electrode, and charged droplets and ions generated by electrospray pass through the electrode hole and irradiate the analysis sample as a beam.
The ionic liquid supply line is a tube having an inner diameter of about 100 μm, for example, a PEEK tube. Moreover, it has a liquid supply mechanism (for example, a microsyringe) (not shown), and can continuously supply the ionic liquid to the metal thin tube. The ionic liquid supply line and liquid supply mechanism can be installed in a vacuum or at atmospheric pressure, but when installed under atmospheric pressure, the tip of the metal thin tube is installed inside the vacuum vessel, and the electrospray itself is The structure can be performed in a vacuum.

(Example 5)
FIG. 5 is a schematic diagram of Embodiment 5 of the present invention. The basic configuration is the same as that of the fourth embodiment shown in FIG. 4, but is characterized in that a deceleration electrode and a ground electrode are arranged downstream of the counter electrode. The deceleration electrode and the ground electrode are each provided with an electrode hole so that a beam generated by electrospray can pass therethrough.
The deceleration electrode has a structure to which a high voltage is applied, and has a function of decelerating charged droplets and ions generated by electrospray. In the beam generated by electrospray, roughly classified,
Two components, i.e., a component having a small mass-to-charge ratio (m / z) and (ii) a component having a large mass-to-charge ratio (m / z) are mixed. By adjusting the voltage applied to the deceleration electrode, it is possible to prevent a component having a small mass-to-charge ratio (m / z) mixed in the beam from passing through the deceleration electrode. That is, by adjusting the deceleration electrode voltage, a component having a small mass-to-charge ratio (m / z) can be removed from the beam. As a result, it is possible to generate a beam composed only of components having a large mass-to-charge ratio (m / z).
If a component having a small mass-to-charge ratio (m / z) is present in the beam, the analysis sample may be damaged when the analysis sample is a soft material such as an organic material or a biological substance. Therefore, when analyzing an organic material, it is desirable to remove a component having a small mass-to-charge ratio (m / z) and to irradiate a beam consisting only of a component having a large mass-to-charge ratio (m / z).
FIG. 6 is a conceptual diagram of an experimental apparatus used for verifying the effect of the deceleration electrode. The tip of the metal thin tube is installed inside the vacuum vessel, and has a structure in which ionic liquid can be electrosprayed in vacuum. The ionic liquid beam generated by electrospraying in vacuum passes through the counter electrode, deceleration electrode, ground electrode (A), deflection electrode, and ground electrode (B), reaches the target, and the beam current value is measured using an oscilloscope. Measured. The deflection electrode is composed of two flat plates, one flat plate is grounded, and a pulse voltage is periodically applied to the other flat plate. In the experiment, a voltage of +1 kV was applied to the deflection electrode periodically (100 Hz) for 2000 μs. Note that the time when the pulse voltage of +1 kV was not applied was maintained at 0V. During the application of +1 kV, the beam trajectory is bent by the generated electric field, the beam cannot reach the target, and after a while, the beam current value measured by the target becomes zero. On the other hand, when the voltage is decreased from +1 kV to 0 V, the beam reaches the target. The feature of this experimental apparatus is that the mass-to-charge ratio (m / z) of charged particles existing in the beam and the current value of each current component can be evaluated by examining the transient response of the target current.

FIG. 7 is an example of the results of a transient response experiment measured using the experimental apparatus of FIG. The transient response of the target current was examined by applying a pulse voltage to the deflection electrode periodically while applying a voltage of +1.6 kV to the metal thin tube steadily and continuously electrospraying the ionic liquid. The lower rectangular wave in the figure is the voltage applied to the deflection electrode. The voltage was maintained at 0 V between t = 0 μs and 1000 μs and between t = 3000 μs and 4000 μs, and +1 kV was applied between t = 1000 μs and 3000 μs. Immediately after +1 kV is applied to the deflection electrode (t = 1000 μs), the ionic liquid beam is electrostatically bent, the target current starts to decrease, and becomes zero after several hundred μs. Further, when the voltage of +1 kV applied to the deflection electrode is reduced to 0 V (t = 3000 μs), the target current starts to increase after a while and recovers to a steady value after several hundred μs.
By analyzing the time response until the target current recovers with the time when the deflection electrode voltage is instantaneously decreased from +1 kV to 0 V (t = 3000 μs) as a reference, it exists in the beam. The m / z of the charged particle component can be evaluated. Formula (1) shows the relationship between the time of flight of charged particles and the mass-to-charge ratio (m / z).
m / z = 2eVt ² / (uL ² ) (1)
Here, e is the elementary charge (1.6022 × 10 ⁻¹⁹ C), V is the acceleration voltage, t is the flight time, u is the unit of unified atomic mass (1.66054 × 10 ⁻²⁷ kg), and L is the flight distance. It is.
In FIG.
(I) The transient response result of the target current when the deceleration voltage is 0 V and (ii) the transient response result of the target current when the deceleration voltage is +1.5 kV are compared. When the deceleration voltage is 0V, it can be confirmed that the recovery process of the target current consists of two stages, a fast process and a slow process. On the other hand, when the deceleration voltage is +1.5 kV, it can be seen that there is no fast recovery process and only a slow recovery process.
Specifically, when the deceleration voltage is 0 V, the target current is rapidly recovered from the time when the deflection electrode voltage is decreased from +1 kV to 0 V (t = 3000 μs) in several + μs (one step of the recovery process). Eye). Thereafter, the target current further increased after several hundred μs and recovered to a steady value (second stage of the recovery process). That is, it can be seen that under the condition that the voltage applied to the deceleration electrode is low, a component having a small mass-to-charge ratio (m / z) and a component having a large mass are mixed in the ionic liquid beam.
On the other hand, when the deceleration electrode voltage is set to +1.5 kV, a fast recovery process of the target current does not appear after several tens of μs from the time (t = 3000 μs) when the deflection electrode voltage is set to 0 V, and after about several hundreds of μs. It can be confirmed that it is only a recovery process. The reason why the component having a small mass-to-charge ratio (m / z) has a relatively small energy, so it cannot overcome the wall of the electrostatic potential formed by the deceleration electrode and cannot travel downstream from the deceleration electrode. it is conceivable that.

  FIG. 8 shows the results of summarizing changes in the small and large components of the mass-to-charge ratio (m / z) relative to the deceleration electrode voltage. From this figure, it can be seen that by adjusting the deceleration voltage, a component having a small mass-to-charge ratio (m / z) can be removed and a beam consisting only of a component having a large mass-to-charge ratio (m / z) can be generated. The reason why the current value increases near the deceleration voltage of 0.9 kV is considered to be that the electric field formed by the deceleration electrode acts to focus the ionic liquid beam.

(Example 6)
FIG. 9 is a schematic diagram of Embodiment 6 of the present invention. The difference from the SIMS apparatus of FIG. 3 (Embodiment 3) or FIG. 4 (Embodiment 4) is that the ionic liquid beam source also serves as the primary ion beam source instead of the dedicated primary ion beam source. It is a feature.
FIG. 10 is a conceptual diagram of a SIMS experimental apparatus equipped with an ion beam source using electrospray of an ionic liquid in a vacuum. The ionic liquid beam source also serves as a primary ion beam source for SIMS. The mass spectrometer is equipped with a time-of-flight mass spectrometer (TOF-MS), and the mass-to-charge ratio (m / z) of secondary ions released from the analytical sample is measured for the time of flight of the secondary ions. Can be evaluated. In the experiment, an ionic liquid A was applied to a stainless steel plate to obtain an ion beam target. In addition, the ionic liquid B is supplied to the metal thin tube using a microsyringe pump and PEEK tube (not shown) under the condition of 50 nL / min, and the ionic liquid beam is constantly generated by electrospraying inside the vacuum vessel. The target was irradiated continuously. Secondary ions sputtered from the target surface by ionic liquid beam irradiation are transported to a time-of-flight mass spectrometer via an electrostatic lens and subjected to mass analysis.
The ionic liquid A is N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) amide, and is hereinafter referred to as DEME-TFSA. DEME-TFSA (molecular weight 426.07) is derived from cation DEME (C ₈ H ₂₀ ON, molecular weight 146.15) and anion TFSA (N (SO ₂ CF ₃ ) ₂ , molecular weight 279.91). Composed.
Moreover, the ionic liquid B is 1-Ethyl-3-methylimidazoliumbis (trifluoromethanesulfonyl) amide, and is hereinafter referred to as EMI-TFSA. EMI-TFSA (molecular weight 391.00) is cation EMI (C ₆ H ₁₁ N ₂ , molecular weight 111.09) and anion TFSA (N (SO ₂ CF ₃ ) ₂ , molecular weight 279.91). Consists of
N (SO ₂ CF ₃ ) _{2 which} is an anion may be referred to as TFSI, NTf ₂ , Tf ₂ N or the like in addition to TFSA, but based on the IUPAC nomenclature, It will be referred to as TFSA.

FIG. 11 is a first example of a mass spectrum of secondary ions measured using the SIMS apparatus shown in FIG. The voltage of the metal thin tube was 7.25 kV, and the voltage of the counter electrode was 6.0 kV. During the measurement, the gas pressure in the ionic liquid beam irradiation part was 2 × 10 ⁻⁴ Pa, and the gas pressure in the mass analysis part was 1 × 10 ⁻⁵ Pa. In FIG. 11, the largest peak is a cation (DEME, m / z 146.15) of the target ionic liquid A (DEME-TFSA). An ion (m / z 572.22) obtained by adding a cation (DEME) to the ionic liquid A molecule (DEME-TFSA) also showed a relatively high strength. Further, secondary ions derived from ionic liquid B (EMI-TFSA) ionized by electrospray were also detected. For example, m / z 111.09 is an EMI-TFSA cation (EMI). Moreover, the ion (m / z 502.10) which added the cation (EMI) to EMI-TFSA was also detected. Note that a relatively strong signal is also obtained at m / z 537.16, which is considered to be an ion obtained by adding a cation (EMI) of the ionic liquid B to the ionic liquid A (DEME-TFSA).
An interesting point in the result of FIG. 11 is that in addition to secondary ions caused by the ionic liquid A applied on the target, secondary ions caused by the ionic liquid B irradiated as an ion beam were also detected. . For this reason, not only “sputtering of the analytical sample on the target” but also “deposition of the ionic liquid on the surface of the analytical sample” and “sputtering of the deposited ionic liquid” are performed simultaneously in the ionic liquid beam irradiation. It is thought that it is carried out. Therefore, it is considered that the sputtering effect and the deposition effect can be adjusted by adjusting the irradiation condition of the ionic liquid beam, and as a result, the amount of the ionic liquid on the surface of the analysis sample can be controlled.

  FIG. 12 is a second example of a mass spectrum of secondary ions measured by the SIMS apparatus shown in FIG. Polyethylene glycol (average molecular weight 300, hereinafter referred to as PEG300) was applied to the target stainless steel plate. An ionic liquid B (EMI-TFSA) was supplied to the metal thin tube, and the ionic liquid beam was continuously irradiated. The voltage of the metal thin tube was 8.7 kV, and the voltage of the counter electrode was 7.0 kV. Secondary ions as shown in FIG. 12 were generated from the analysis sample (PEG 300) irradiated with the ionic liquid beam. In FIG. 12, m / z 133.1 and m / z 177.1 are characteristic fragment ions of PEG300. Moreover, the secondary ion resulting from PEG300 can be confirmed at m / z 282 to m / z 458. Further, although not shown in FIG. 12, secondary ions (m / z 111.09 and m / z 502.10, etc.) caused by ionic liquid B (EMI-TFSA) irradiated as an ion beam are also detected. It was confirmed that sputtering and deposition by an ionic liquid beam proceeded in parallel.

(Example 7)
FIG. 13 is a schematic diagram of Embodiment 7 of the present invention. The basic configuration is the same as in FIG. 9 (Embodiment 6), but is characterized in that the ionic liquid beam source has a structure in which a deceleration electrode, a focusing electrode, and an XY deflection electrode are added.
By adjusting the voltage applied to the deceleration electrode, components having a small mass-to-charge ratio (m / z) mixed in the ionic liquid beam can be removed, and only from charged droplet components having a large mass-to-charge ratio (m / z). Can be generated. In addition, the focusing electrode can be used to focus the ionic liquid beam and reduce the beam diameter. An example of the focusing electrode is an Einzel lens. Further, the trajectory of the ionic liquid beam can be two-dimensionally scanned by the XY deflection electrode. This makes it possible to irradiate a predetermined position with an ion beam.
The mechanism for removing components with a small mass-to-charge ratio (m / z) mixed in the ionic liquid beam is not limited to the deceleration electrode, and another method using a magnetic field or an electric field is adopted. May be.

(Example 8)
FIG. 14 is an eighth embodiment of the present invention and shows changes in the acceleration voltage of the ionic liquid beam and operation modes. The occurrence or extent of the sputtering phenomenon and deposition phenomenon varies greatly depending on the energy of the ionic liquid beam. Therefore, by controlling the acceleration voltage of the ionic liquid beam, it is possible to adjust the effects of sputtering and deposition caused by the ionic liquid beam irradiation. For example, by lowering the acceleration voltage, it is possible to cause only deposition without causing sputtering at all. Also, by increasing the acceleration voltage, the influence of deposition can be reduced and the effect of sputtering can be increased. Accordingly, the condition where the acceleration voltage is low is a coating mode in which the ionic liquid is supplied to the analysis sample. On the other hand, under a condition where the acceleration voltage is high, the sputtering phenomenon becomes dominant, so that the analysis mode in which secondary ions are released from the surface of the analysis sample is obtained. That is, switching between the coating mode and the analysis mode is possible by controlling the acceleration voltage. As a result, the amount of ionic liquid on the surface of the analysis sample can be controlled within a predetermined range from the start to the end of analysis, and stable measurement can be performed.
It is desirable that the ionic liquid layer on the surface of the analysis sample is not thicker than necessary. In the present invention for supplying an ionic liquid as an ion beam, the deposition amount of the ionic liquid can be accurately adjusted by controlling the acceleration voltage, the beam current, etc., and this is advantageous from the viewpoint of controllability of the coating amount of the ionic liquid. It is thought to have.

By the way, in the case of a SIMS device (so-called TOF-SIMS) using a time-of-flight mass spectrometer (TOF-MS) that measures the time of flight of secondary ions, the measured time-of-flight is expressed as the mass-to-charge ratio (m / z ) Conversion work is required. According to the present invention, since known secondary ions caused by the ionic liquid are always detected, even if the analysis sample is an unknown substance, the time-of-flight and mass-to-charge ratio (m / z) conversion or One of the advantages of the present invention is that the TOF-SIMS system can be easily and accurately calibrated.
In addition, when the analysis sample is made of a composite material or a material having a complicated composition and the outside of the analysis sample has conductivity, but the inside is insulative, the SIMS analysis extends to the inside of the sample. This will cause a charge-up problem. However, when ionic liquid beam irradiation is used, there is no charge up problem. In other words, the present invention can be said to be an effective technique regardless of whether or not the ionic liquid is impregnated or covered in advance before analysis.

  According to the present invention, analysis in vacuum (SEM, TEM, MALDI, SIMS, etc.) of an electrically insulating material or a biomedical sample containing moisture can be performed stably from the start of analysis to the end of analysis. It becomes possible to implement with high accuracy and high sensitivity.

Claims (6)

An apparatus that irradiates an analysis sample with an electron beam, laser, or ion beam and quantitatively analyzes electrons and ions emitted from the analysis sample,
Comprising an ionic liquid beam source for supplying illumination to the ionic liquid ionic liquid beam with respect to the analysis sample in the vacuum chamber, at start of analysis the amount of coating said ion liquid replenished in a vacuum of the analysis sample surface The analyzer can be held stably from the end of the analysis to the end of the analysis.   The analyzer according to claim 1, wherein the ionic liquid beam source is based on electrospray of an ionic liquid in a vacuum.   The ionic liquid beam source has a decelerating part in the middle of transport of an ionic liquid beam generated by electrospray, and separates a component having a small mass-to-charge ratio m / z mixed in the beam and removes it from the beam. The analyzer according to claim 2.   The analyzer according to claim 3, wherein the ion liquid beam source is also used as a primary ion beam source to analyze the mass of secondary ions.   The deceleration unit is composed of a deceleration electrode, and by adjusting the voltage applied to the deceleration electrode, a component having a small mass-to-charge ratio m / z mixed in the beam is prevented from passing through the deceleration electrode, and the mass charge 5. The analyzer according to claim 4, wherein the analysis sample is irradiated with a beam consisting only of a component having a large ratio m / z to analyze the mass of secondary ions. An accelerating voltage control means for controlling the accelerating voltage of the ionic liquid beam is provided, and the accelerating voltage is adjusted by the accelerating voltage control means, whereby the ionic liquid is supplied to the surface of the analysis sample and coated. 6. The analyzer according to claim 4, wherein the mass of the secondary ions is analyzed while appropriately switching the analysis mode for generating the secondary ions.

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