JP2001076663A - Electron radiating device used for photoelectron spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To radiate a large quantity of low-energy electrons to a sample at uniform density by arranging an earth electrode protrusively from an extracting electrode on the outside of the extracting electrode, so that the electrons extracted by the extraction electrode are decelerated to reach the sample by the electric field formed in cooperation with the extraction electrode. SOLUTION: A filament 2 arranged around a grid 1 is excited and heated, and the thermoelectrons generated from the filament 2 are accelerated toward the grid 1. Since a repeller electrode 3 having the same potential as that of the filament 2 is arranged on the outside of the filament 2, the electrons passing through the grid 1 are again pushed back to the grid 1 side, thereby the space with a high electron density is formed in the cylindrical grid 1 to serve as an electron source. An electron beam from the electron source is generated by extracting the electrons existing in the grid 1 with the electric field formed by the extraction electrode 4, repeller electrode 3, and the grid 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron irradiation device for neutralizing a sample in a photoelectron spectrometer using X-rays as a primary excitation source.

[0002]

2. Description of the Related Art In a photoelectron spectroscopy apparatus using an X-ray as a primary excitation source, when a sample is an insulator, photoelectrons are emitted from the sample, and the sample surface is positively charged, which often hinders analysis. In order to neutralize and alleviate this, a method of irradiating low energy electrons is known.

[0003] Electron irradiation devices used for such purposes include (1) that the amount of irradiated electrons is as large as possible, (2) that the electron energy is as low as possible,
(3) It is required to have a performance such that the large area on the sample surface is irradiated with electrons as uniformly as possible. In particular, the performance of the item (3) is important when the irradiation area of the X-ray on the sample is large.

[0004]

However, none of the electron irradiators used for neutralizing charge in the conventional photoelectron spectroscopy satisfies all of the above conditions, so that the charge cannot be sufficiently alleviated. In some cases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the electron irradiation apparatus used in the conventional photoelectron spectroscopy apparatus, and is intended to irradiate a sample with a large amount of low energy electrons at a uniform density on a sample. An object of the present invention is to provide an electron irradiation device for a spectroscopic device.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a cylindrical grid made of a mesh, and a filament disposed around the grid and having a negative voltage applied to the grid. A cylindrical repeller electrode disposed outside the filament and having a negative voltage of the same potential as the filament applied thereto, for accumulating thermoelectrons generated from the filament inside the grid; and a repeller electrode outside the cylindrical repeller electrode. A cylindrical extraction electrode for extracting the electrons stored in the grid, which is disposed and to which a positive voltage is applied, and an electric field formed in cooperation with the extraction electrode is used to sample the electrons extracted by the extraction electrode. And a ground electrode protruding from the extraction electrode and arranged outside the extraction electrode so as to be decelerated to reach It constitutes a child irradiation device.

In the electron irradiating apparatus having the above-mentioned structure, not a point light source but an electron trapped and accumulated in a potential valley having a certain size inside the grid is used as an electron source. The accumulated electrons are extracted by an extraction electrode, decelerated, and irradiated onto the sample surface. At that time, an electric field (potential distribution) is realized so that the electrons do not return or diverge. Since the ground electrode is provided, it is possible to irradiate the sample with a large amount of low-energy electrons of several eV or less at a uniform density.

[0008]

Next, an embodiment will be described. FIG. 1 is a sectional view showing an embodiment of an electron irradiation device used for a photoelectron spectroscopy device according to the present invention. In FIG. 1, reference numeral 1 denotes a grid formed in a cylindrical shape with a mesh, 2 denotes a filament arranged annularly apart from the outer periphery of the grid 1, 3 denotes a cylindrical repeller electrode disposed outside the filament 2, Reference numeral 4 denotes a cylindrical extraction electrode which also serves as a lens electrode and is disposed outside the repeller electrode 3. Reference numeral 4 denotes a further extraction electrode 4.
Is a cylindrical ground electrode arranged outside the. Each of the constituent members is held by the insulator 6 and connected to the current introduction terminal 7. In addition, 8 is a mounting port of the vacuum container, and 9 is a sample.

[0009] As shown in FIG. 2, an operating power supply and the like are connected to the electron irradiation apparatus having such a configuration. That is, the filament heating power supply 11 is connected to the filament 2, and the filament 2 is connected to the grid 1.
A positive terminal of a fixed power supply 12 of several tens of volts to 200 volts (preferably 150 volts) for effectively drawing thermoelectrons generated from the grid side to the grid side is connected. It has become. And
The current of the electrons finally flowing into the grid 1 is called an emission current. The heating current flowing through the filament 2 using a constant emission circuit is feedback-controlled so that the emission current is constant.

The constant emission circuit includes an emission current detection resistor 13 connected between the filament 2 and the negative terminal of the fixed power supply 12 for grid, and a connection point between the fixed power supply 12 and the emission current detection resistor 13 connected to one input terminal. The other input terminal is provided with a differential amplifier 15 having a negative terminal connected to the filament 2 and a positive terminal of an emission current setting power supply 14 connected to the filament 2. An output of the differential amplifier 15 is used to connect the filament heating power supply 11 to the filament heating power supply 11. It is configured to control. An emission current monitoring meter 16 is connected between the emission current detection resistor 13 and the filament 2.

The filament 2 and the repeller electrode 3 are connected to a negative terminal of an accelerating voltage setting power source 17 having a positive terminal connected to the ground, and the extraction electrode 4 is connected to an extraction voltage having a negative terminal connected to the ground. The positive terminal of the setting power supply 18 is connected.

Next, the operation of the thus configured electron irradiation apparatus will be described. The filament 2 arranged around the grid 1 is energized and heated, and the thermoelectrons generated from the filament 2 are accelerated in the grid direction. In addition, since the repeller electrode 3 having the same potential as the filament 2 is disposed outside the filament 2, electrons passing through the grid 1 are pushed back to the grid side. In this way, a space (electron reservoir) having a high electron density is generated inside the cylindrical grid 1 and serves as an electron source. This method is basically based on the same operation principle as a vacuum gauge ionization chamber called BA type. However, in the present embodiment, the purpose is not to ionize but to form a reservoir of electrons. I have. The size of the electron reservoir is preferably about 10 mm in diameter. Since the electron beam generated from this electron source has a uniform electron density without being affected by the filament shape, the electron irradiation area on the sample surface is large and the current density is uniform.

An electron beam from the electron source is generated by extracting electrons existing inside the grid by an electric field formed by the extraction electrode 4, the repeller electrode 3 and the grid 1. The lens action on the electron beam generated from the extraction portion is realized by an electric field formed by the extraction electrode 4 and the ground electrode 5. This gives the number e
Even a very low energy electron of about V can reach the sample while maintaining a certain degree of convergence.

According to the study of the present inventor, although it depends on the working distance (the distance from the tip of the ground electrode of the electron irradiation device to the sample), in the case of a working distance of about 100 mm, the extraction electrode 4 on the sample side is not used. By lengthening the earth electrode 5 so that it protrudes to about 10 mm from the end, the electric field generated in the lens portion oozes out to the vicinity of the sample, not only in the lens portion, but as shown in FIG. As shown, even with very low energy electrons, the extracted electrons 21 can reach the sample surface. On the other hand, if the length of the ground electrode 5 is too long, as shown in FIG. 4, the electrons 22 with extremely low energy cannot reach the sample surface and return.

As described above, according to the present embodiment, the electron reservoir formed inside the cylindrical grid 1 is used as an electron source, and is not a point light source but is caught in a potential valley having a certain size. And a function of extracting electrons by an electric field formed by the extraction electrode 4, the repeller electrode 3 and the grid 1 to which a high voltage is applied,
It has a function of decelerating electrons by an electric field formed by the extraction electrode 3 and the earth electrode 5 and does not return or diverge the projected length of the earth electrode 5 before the electrons reach the sample surface. Such a potential distribution is realized so that a large electron flow can be obtained even in a low energy region of several eV or less. Accordingly, the sample can be irradiated with a large amount of low-energy electrons of several eV or less at a uniform density.

[0016]

As described above with reference to the embodiments, according to the present invention, the amount of the irradiated electrons is as large as possible, the energy of the electrons is as low as possible, and the electrons are in a large area on the sample surface. An electron irradiator that irradiates the sample as uniformly as possible can be realized, and it is possible to effectively prevent the insulating sample from being positively charged by the photoelectron spectroscopy device and disturbing the analysis. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an electron irradiation device for a photoelectron spectroscopy device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a connection mode of an operation power supply to each unit in the embodiment shown in FIG.

FIG. 3 is a diagram showing a mode in which electrons extracted from the electron irradiation device according to the embodiment shown in FIG. 1 reach a sample surface.

FIG. 4 is a diagram showing a mode in which, when a long ground electrode is formed, extracted electrons cannot reach the sample surface and return in the middle.

[Explanation of symbols]

 Reference Signs List 1 grid 2 filament 3 repeller electrode 4 extraction electrode 5 ground electrode 6 insulator 7 current introduction terminal 8 vacuum vessel mounting port 9 sample 11 filament heating power supply 12 grid fixed power supply 13 emission current detection resistor 14 emission current setting power supply 15 differential amplifier 16 Emission current monitor meter 17 Acceleration voltage setting power supply 18 Extraction voltage setting power supply

Claims (1)

[Claims] 1. A cylindrical grid formed of a mesh, a filament disposed around the grid and applied with a negative voltage to the grid, and a negative voltage disposed outside the filament and having the same potential as the filament. And a cylindrical repeller electrode for storing thermoelectrons generated from the filament inside the grid, and a thermoelectric electron stored outside the repeller electrode and applied with a positive voltage. A cylindrical extraction electrode for extracting the extracted electrons, so that an electric field formed in cooperation with the extraction electrode has a form in which the electrons extracted by the extraction electrode are decelerated and reach the sample. An electron irradiation device for use in a photoelectron spectroscopy device, comprising: an earth electrode disposed outside and protruding from the extraction electrode.