JPH09189680A - Micromass spectrograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the mass of materials that desorb from a sample to be analyzed at each site of the sample by collecting the materials into a hollow tube through an opening, and guiding them into a mass spectrograph. SOLUTION: A voltage is applied between a hollow tube 4 composed of a conductor 5 and a sample 2 to bring the end of an opening in the hollow tube 4 close to the sample 2, and the distance between the sample 2 and a probe 6 attached to the opening in the hollow tube 4 is held between 1nm and several hundred nm by a current flowing between the probe 6 and the sample 2, and the surface configuration of the sample 2 is measured by tracing the surface of the sample 2 with the probe 6. At the same time, only materials that desorb from portions near immediately below the opening are guided into the hollow tube 4 and into a mass spectrograph 1. Thus the mass of the desorbed materials can be analyzed at each site of the sample 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a mass spectrometer.

[0002]

A mass spectrometer is an analyzer for measuring the mass of a substance. Since the mass of a substance differs depending on the type, the type of substance can be identified by a mass spectrometer. Since it is possible to specify the type of substance, it is used to identify the gas in the atmosphere, determine the composition of the sample, and elucidate the chemical reaction on the sample surface.
As a measurement example using this, thermal desorption spectroscopy (Thermal Dilation
absorption spectroscopy (TDS). This is because the sample temperature is raised, the desorbing gas is measured with a mass spectrometer, the gas is specified from the mass, the relationship between the temperature and the desorbed gas is investigated, and the state of adsorbed molecules on the sample surface This is a method of examining the chemical reaction of. However, since TDS raises the temperature of the entire sample and observes the mass of the gas released from the entire sample with a mass spectrometer, it does not have the positional resolution as to which gas is released from which part of the sample. . For example, the catalytic reaction depends on the shape of the catalyst surface, but in TDS, the correlation between the shape and the catalytic reaction is completely unknown. In addition, the secondary ion mass spectrometry (Secondary Ion M
Ass Spectroscopy (SIMS) does not have position resolution like TDS.

Scanning Tunnelin
g Microscope: STM) and atomic force microscope (Atomic Fo
The rce microscope (AFM) is a microscope with a position resolution that allows direct observation of atoms on the sample surface. STM is
This is a device for measuring the sample surface shape by tracing the sample surface shape with the probe by using a tunnel current flowing when a sharp pointed probe and the sample are made to approach each other by about 1 nm while applying a voltage. On the other hand, the AFM is an apparatus for measuring the surface shape of a sample by bringing the tip of a minute lever close to the sample, detecting an atomic force acting between the lever and the sample by lever deflection. There are many samples that use these techniques to observe the physical and chemical properties of the surface. However, neither device can identify the constituent substance on the sample surface. Therefore, only the surface shape of a sample having a complicated structure is measured.

[0004]

As described above, in the existing mass spectrometric method, since all the substances desorbed from the sample surface are observed, it is not possible to know the correlation between the sample location and the desorbed substance. Can not. On the other hand, the STM and the AFM have the positional resolution enough to observe the atoms on the surface of the sample, but have the drawback that the substance cannot be specified. Therefore, the measurable sample is limited to a simple sample.

It is an object of the present invention to provide a method and apparatus for combining the local observation technology of STM or AFM with the mass analysis technology of a mass spectrometer to locally perform mass analysis to specify the type of substance. is there.

[0006]

The present invention is directed to a mass spectrometer for measuring mass, a hollow tube having an opening at its tip for guiding a substance desorbed from the sample to the mass spectrometer, and a sample. A small probe provided at the tip of the hollow tube to trace the surface, a control mechanism that keeps the distance between the tip of the hollow tube and the sample at a fixed distance, and a scan that scans the sample surface with the tip of the hollow tube A drive mechanism, a control device for controlling the scanning drive mechanism, a desorption mechanism for desorbing a substance from a sample, a control device for controlling the desorption mechanism, and a mass spectrometer for all the substances taken into the hollow tube. In order to introduce the above into the hollow tube, a heating mechanism for heating the hollow tube so that a substance does not adhere to the inner wall of the hollow tube, and an exhaust device for evacuating the hollow tube are provided.

Further, according to the present invention, control is performed by using a current flowing between the sample and the probe attached to the opening of the hollow tube, and the distance is set to 1 nm to several hundreds of nm to directly under the opening. It is a micro-mass spectroscope that can perform mass spectrometric analysis only on substances that desorb from the vicinity.

Further, according to the present invention, the tip of the opening of the hollow tube is brought close to the sample, and the surface shape is measured by tracing the surface of the sample with a probe attached to the opening, and at the same time, the surface shape is measured immediately below the opening. It is a micro-part mass spectroscope that can perform mass spectrometric analysis only on substances that are separated.

The conventional mass spectrometer has no position resolution,
The mass of the substance desorbed from the entire surface of the sample was measured. Therefore, it is completely unknown from which part of the sample what kind of substance is desorbed. Therefore, bring the open end of the hollow tube close to the sample, collect only the substances that desorb from directly below the open end into the hollow tube, and guide only the substances in it to the mass spectrometer. Analysis is possible. Since the position resolution of mass spectrometry depends on the distance between the opening and the surface and the size of the opening, it is necessary to make the distance as short as possible and make the opening small. In contrast to shortening the distance, in the present invention, a probe is provided at the tip of the opening, and a tunnel current that flows when the probe and the sample are brought close to each other while applying a voltage is used. It is possible to keep the distance of 1 nm to several hundreds of nm. As a result, only the substance desorbed from the area immediately below the opening can be introduced into the hollow tube. By tracing the sample surface with the tip of a probe provided at the opening of the hollow tube, it is possible to analyze the mass of the detached substance and simultaneously observe the surface shape. The size of the opening can be up to several tens of nm in diameter by recent microfabrication technology, and by using this technology, the size of the opening of the hollow tube of the micro-mass spectrometer of the present invention can be increased. Can be manufactured with a diameter of several tens of nm, and the position resolution of the minute part mass spectrometer is about several tens nm. Although the example in which the tunnel current is used to control the distance between the opening and the sample has been described, the present invention is not limited to using the tunnel current to control the distance between the opening and the sample. Atomic force, Coulomb force, evanescent light, fluorescence, etc. acting between the sample and the probe can be used to control the distance between the opening and the sample.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is an explanatory diagram comparing a micro-part mass analysis method (a) according to the present invention with a conventional mass analysis method (b). 1 is a mass spectrometer, 2 is a sample, 3 is a substance desorbed from the sample, and 4 is a hollow tube. In the conventional mass spectrometry method, all the substances desorbed from the whole sample were measured, but by moving the tip of the hollow tube close to the sample, only the substance desorbed from the sample directly below the hollow tube is Then, only the substance in the hollow tube is guided to the mass spectrometer, which enables mass analysis for each place.

FIG. 2 is an enlarged view of the tip of the hollow tube. The tip portion is open, and the desorbed substance is taken into the hollow tube from there. In addition, a probe is provided at the tip of the hollow tube,
Trace the sample surface with the tip of this probe to observe the surface shape. Here, by controlling the current flowing between the probe provided at the tip of the hollow tube and the sample, the distance between the hollow tube and the sample is controlled, and the shape of the sample surface is observed. is there. Therefore, the probe and the sample are required to be conductors. Reference numeral 5 is a conductor, and 6 is a probe. There are two different cases: an example in which the hollow tube itself is made of an electric conductor for use in controlling the electric current (a), and an example in which the hollow tube is an insulator and is made conductive by attaching an electric conductor to the surface. A hollow tube is shown.

FIG. 3 shows a micro-mass spectrometer according to the present invention. Here, an apparatus for measuring the substance desorbed from the sample due to the temperature rise at each place is shown. Reference numeral 7 is a sample heating mechanism, 8 is a sample heating mechanism control device, 9 is a power source and current detection unit, 10 is a hollow tube scanning mechanism, 11 is a hollow tube scanning control device, and 12 is a substance desorbed from the sample in the hollow tube. A hollow tube heating mechanism for preventing adhesion to the inner wall of the device, 13 an evacuation device for keeping the inside of the hollow tube and the mass analyzer vacuum, and 14 a surface shape and a display part of the mass analysis result. The part surrounded by the broken line is placed in a vacuum chamber and is evacuated to a vacuum as in the hollow tube. In order to make the inside of the hollow tube vacuum, a dedicated exhaust device was installed because the inside of the hollow tube cannot be evacuated even if the outside of the hollow tube is vacuum if the area of the opening of the hollow tube is small. Is. In order to control the distance between the sample and the hollow tube, the current flowing through the sample and the hollow tube is used here.

(Embodiment 2) FIG. 4 is a view showing a method in which no current is used for controlling the distance between the hollow tube and the sample. Reference numeral 15 is a minute lever for detecting the interatomic force. A minute probe and an opening are provided at its tip. The substance released from the sample passes through this opening and is guided into the hollow tube through the opening on the back surface of the minute lever. Although the tip of the micro-lever and the hollow tube are not connected in the example, this is because the micro-lever bends by a force of 10 ⁻⁹ Newton, and the surface shape of the sample is observed by utilizing this bending, so that This is because if you do not connect the micro lever, the micro lever will be bent by the hollow tube. As long as it is a flexible hollow tube that does not bend the lever, it does not matter even if it is connected to the small lever.

[0014]

According to the present invention, it is possible to analyze the mass of the substance desorbed from the sample for each place of the sample. Further, it is possible to identify the type of desorbed substance by mass spectrometry.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a process in which a desorbed substance enters a mass spectrometer of a micro-mass spectrometer according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a minute portion mass spectrometer according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a minute section mass spectrometer equipped with a desorption device for desorbing a substance from a sample in the minute section mass spectrometer of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a minute portion mass spectrometer according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mass spectrometer, 2 ... Sample, 3 ... Desorption substance, 4 ... Hollow tube, 5 ... Conductor, 6 ... Probe, 7 ... Sample heating mechanism, 8 ... Sample heating mechanism controller, 9 ... Power supply and Current detector, 10
... Hollow tube scanning mechanism, 11 ... Hollow tube scanning mechanism controller, 1
2 ... Hollow tube heating mechanism, 13 ... Hollow tube exhaust device, 14 ...
Surface shape and mass spectrometry result display area, 15 ... Micro leverage.

Claims (4)

[Claims] 1. A hollow tube having a probe at the tip of an opening for taking in a substance, wherein the hollow tube is brought close to a sample surface, and the substance desorbed from the sample is passed through the opening to the hollow tube. A mass spectrometer, which measures the mass of a substance by collecting the substance in a tube and guiding only the collected substance to a mass spectrometer. 2. A hollow tube made of a conductor or the hollow tube having an outer surface covered with a conductive substance is used.
Detach from the sample by applying a voltage between the sample and its conductor to bring it close to the surface, and using the current flowing between the sample and the conductive substance to set the distance between the tip of the capillary and the sample to 1 nm to 300 nm. A mass spectroscope characterized by achieving a submicron position resolution by introducing an incoming substance into a hollow tube through an opening and guiding only the extracted substance to a mass spectrometer. 3. The hollow tube according to claim 1 or 2, wherein the hollow tube is attached to a scanning drive mechanism, and an electric current flowing between the sample and a probe provided at a tip of an opening of the hollow tube is used. A mass spectrometer that measures the shape of the sample surface and at the same time observes the mass of the desorbed substance passing through the hollow tube. 4. The mass spectrometer according to claim 1, further comprising a vacuum exhaust device for keeping the hollow tube and the mass analyzer vacuum.