JP2764505B2 - Electron spectroscopy method and electron spectrometer using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron spectroscopy apparatus for performing energy analysis of electrons generated in a pulse form.

[0002]

2. Description of the Related Art The energy distribution of electrons emitted from a substance by irradiation of light, X-rays, electrons, etc. contains information on the state of the substance, such as Auger electron spectroscopy generated by electron beam irradiation. In addition, ultraviolet photoelectron spectroscopy (UPS), which measures photoelectrons generated by irradiation of ultraviolet rays or X-rays, and soft X-ray photoelectron spectroscopy (XPS), are important analysis methods that are essential for studying material states, especially surface states. It has become.

[0003] Conventionally, as an electron spectrometer, a device using a deceleration electric field is often used at the beginning, and a cylindrical mirror type energy analyzer (CMA) is most often used at present (see MP Seah, p. 57, "Methods of surface analysi
s ", ed.JMWalls, (Cambridge University Press, Cambri
dge, 1989).

According to this method, when electrons are made to enter between narrow cylindrical electrodes to which an electrostatic field is applied through a narrow entrance slit, only electrons having a specific energy are focused on a measuring instrument through a narrow exit slit. Using the principle
By knowing the energy distribution of electrons by changing the size of the electrostatic field, it is possible to capture electrons emitted from the sample at a wide solid angle even under high-resolution measurements of 0.25%. The sensitivity of CMA is higher than that of the analyzer.

However, in the case of CMA, only electrons of a specific energy are measured at one set voltage. For example, when measuring at a high energy resolution of 1/1000, the remaining 999/1000 electrons are discarded without being measured, and this extremely low detection efficiency requires a long measurement time. Also, radiation damage to the sample is a problem.

Therefore, an electrostatic hemispherical energy analyzer as shown in FIG. 2 has been developed to increase the measuring speed. This is because, when an electrostatic field is applied between the two spherical electrodes R1 and R2, the trajectory of the electrons incident from the entrance slit S is converged on the exit surface E, and the converging position depends on the electron energy. Therefore, by observing the spatial distribution of the electron beam condensed on the emission surface with a one-dimensional array or a two-dimensional image detector D, electrons in a relatively wide energy range are measured at one time. According to the method, for example, energy analysis can be performed at about 200 times the speed of CMA.

[0007]

However, these conventional electron spectrometers generate from a constantly irradiated sample such as an ultraviolet ray or an X-ray from a synchrotron radiation facility or an X-ray tube, or an electron beam from an electron beam generator. It is designed to measure the number of electrons that are generated, and can also work on multi-point data simultaneously. Even in the above-mentioned electrostatic hemispherical analyzer, the energy range that can be measured at one time is only about 10%.

Further, in order to obtain a certain level of energy resolution in the electrostatic hemispherical analyzer, the angular width α incident on the slit S must be limited to a small value, and there is a problem that the solid angle utilization efficiency is small.

On the other hand, high-intensity pulsed X-rays can be obtained from plasma or X-ray lasers generated by ultrashort pulse lasers in recent years, and pulsed ultrashort wavelength ultraviolet rays can be obtained by generation of harmonics of ultrashort pulse lasers. By using such a high-intensity pulsed radiation source, many fields such as observation of high-speed phenomena of the surface state may be opened even in the field using electron spectroscopy.

However, these high-intensity pulsed radiation sources also have a high peak output but a low average output. On the other hand, in a conventional electron spectroscope designed for a steady irradiation radiation source, the average output is low. Is important, and the high peak power of a high intensity pulsed source cannot be measured.

Therefore, in the present invention, by developing an electron spectroscopy method and its apparatus having high detection efficiency utilizing the above-described features of the high-intensity pulsed radiation source, new techniques such as observation of high-speed phenomena of a sample surface state are developed. The purpose is to enable the development of applied fields.

[0012]

According to the present invention, in order to solve the above-mentioned problems, a sample is irradiated with pulsed X-rays or ultra-short wavelength ultraviolet rays, electrons emitted from the sample are caused to fly a predetermined distance, and the flight time is increased. To provide an electron spectroscopy method for measuring the

Further, according to the present invention, there is provided means for irradiating pulsed X-rays or pulsed ultrashort wavelength ultraviolet light, and a flight path for causing electrons emitted from the sample to fly a predetermined distance when the sample is irradiated with pulsed X-rays or pulsed ultrashort wavelength ultraviolet light. And an electron spectrometer comprising an electron flow measuring means for measuring the time of flight.

That is, when an electron flies over a certain distance, the time of flight depends on the energy of the electron. Then, if the electron flow is observed at a place sufficiently distant from the electron source, the electron energy is spectrally analyzed from the time change. Then, by recording all the time changes, the generated electrons are measured without being discarded wastefully, and the efficiency of the measurement becomes extremely high.

In the present invention, an ultrashort pulse laser-produced plasma or an X-ray laser can be used as the pulse X-ray irradiating means. Waves and the like can be used.

In order to enable the time-of-flight method as in the present invention, it is necessary to make the time width of particle generation sufficiently shorter than the time-of-flight difference to be observed. For example, an electron of 300 eV flies a distance of one meter in 100 nanoseconds (one tenth of a millionth of a second), but at one meter from the electron source, the energy spectrum of an electron of 300 eV averages 1/100. In order to measure with an energy accuracy of, the electron flow measurement requires a time resolution of 2 nanoseconds, and the generation of electrons also requires a shorter pulse width. By using pulsed X-rays that have recently been obtained, it is possible to easily generate electrons having such a pulse width.

In the present invention, when the pulse width of the generated electrons is constant, the energy resolution can be improved by extending the distance of the electron flight path and increasing the flight time.

Further, a deceleration electric field is provided in the middle of the flight path to decelerate the flying electrons.
By slowing down to 40 eV, the flight time can be significantly increased and the energy resolution improved.

Electrons emitted from a substance by irradiation with X-rays or the like are distributed over a wide solid angle. However, a lens formed by an electric or magnetic field is provided on the flight path to allow electrons emitted at a wide solid angle to travel far. By condensing the light in a slit or spot shape on an electron flow measuring instrument installed at a distance from the target, the trapping rate of electrons can be increased.

On the other hand, as an electron flow measuring device for measuring the time of flight of electrons, a device having a time resolution of about 2 nanoseconds and a high sensitivity is required. Such a high sensitivity electron flow measuring device is required. If not, the electron flow measuring device may be constituted by the following means.

That is, the time-of-flight distribution is converted into a spatial distribution by deflecting the electrons in a direction different from the flight direction of the electrons, for example, in a direction orthogonal to the flight direction of the electrons by means of applying an electric field swept over time. If this is the case, a television camera or an image detector can be used, and data processing becomes easy.

Further, as described above, by sweeping and deflecting a spatially limited electron flow through a slit or a pinhole, the energy resolution is kept high.

Further, by applying means such as accelerating electrons at a high speed by applying a high voltage, using a channeltron or a channel plate, or combining them, the electron flow is multiplied to obtain extremely weak electrons. The flow can also be measured.

It is known that the sensitivity of a channel plate or the like depends on the energy of incident electrons. However, the acceleration of electrons due to the application of a high voltage is performed in an energy region where the sensitivity does not greatly depend on the energy. There is an advantage that data processing can be facilitated by accelerating electrons at the same time. However, by shortening the duration of the amplification capability and synchronizing it with the pulsed electron flow, the signal pair can be further increased. The noise ratio can be improved.

[0025]

According to the present invention, electrons emitted from a sample by pulse excitation of an ultrashort pulse X-ray or the like can be separated with extremely high detection efficiency and high resolution. Using excitation of X-rays or the like as measurement means,
It can contribute to the development of new application fields such as research on high-speed development of surface conditions.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention, wherein 1 is a sample, 2 is a pulse X-ray irradiator such as plasma generated by an ultrashort pulse laser, 3 is a deceleration grit, and 4 is a predetermined distance. The electron flow path 5 is an electron flow measuring instrument.

In the present embodiment, the electron flow measuring instrument 5 has a slit 6 at its tip, an accelerating electric field 7 and a deflecting electric field 8 behind the slit 6, and a channel behind the deflecting electric field 8. It is configured by arranging a plate 9, a fluorescent plate 10, an optical lens 11, and a camera 12.

Further, electron lenses 13 are arranged on both sides of the flight path of the electron flow so that the electron flow is focused on the slit 6.

Here, the pulse X-ray from the pulse X-ray irradiator 2
When the line is irradiated on the sample 1, a pulsed electron beam e is generated from the surface of the sample 1. After adjusting the electron energy of the electron beam e with the grit 3, the electron beam e is passed through a long flight path 4, whereby the energy spectrum of the electrons is converted into a time change of the electron flow on the slit 6.

In this embodiment, electron lenses 13 are provided on both sides of the flight path 5, and electrons generated from the sample 1 are condensed on the slit 4 by using the electron lenses 13, so that the electron capture rate is improved. Is to be raised.

Next, after a sufficient time difference is created, the signal is multiplied by accelerating in the accelerating electric field 7. In addition, a time-varying deflection electric field 8 is applied to deflect the electron e in a direction orthogonal to the flight direction, thereby converting the time change of the electron flow into a spatial change, thereby obtaining a one-dimensional array or two-dimensional image. The energy spectrum of the electrons can be easily recorded using a detector.

The electron energy distribution converted into the spatial distribution is amplified by the channel plate 9 or the like, and
After conversion into light, the camera 12
Observe with.

In this case, the signal-to-noise ratio can be improved by applying a pulse voltage or the like so that the channel plate or the like has an amplifying ability only for a short pulse width synchronized with the generation of electrons. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of a conventionally used electrostatic hemispherical energy analyzer.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 sample 2 pulse X-ray irradiator 3 deceleration grit 4 electron flow flight path 5 electron flow measuring instrument 6 slit 7 accelerating electric field 8 deflection electric field 9 channel plate 10 fluorescent plate 11 optical lens 12 camera 13 electron lens e electron beam R1, R2 Two spherical electrodes constituting an electrostatic hemispherical energy analyzer S Entrance slit E Emission surface D One-dimensional array or two-dimensional image detector α Angle width incident on slit S

Claims (7)

(57) [Claims] 1. A sample is irradiated with pulsed X-rays generated from an ultra-short pulse laser-produced plasma, electrons emitted from the sample are caused to fly a predetermined distance, and emitted from the sample.
A flight time difference corresponding to the electron energy is created ,
By measuring the flight time distribution based on the line time difference,
An electron spectroscopy method comprising measuring an energy distribution of electrons emitted from the sample . 2. An irradiation means for irradiating a sample with pulsed X-rays generated from an ultrashort pulse laser-produced plasma ;
When a pulse X-ray is irradiated, electrons emitted from a sample are caused to fly a predetermined distance, and the electrons emitted from the sample are emitted.
A flight path to create a flight time difference according to the energy, the flight
By measuring the flight time distribution based on the line time difference
Electron spectroscopy apparatus characterized by comprising a electronic flow measurement means for measuring the electron energy distribution emitted from the serial sample. 3. An electron spectrometer according to claim 2, further comprising means for decelerating or accelerating an electron flow in a flight path. 4. An electron according to claim 2, wherein a slit or an aperture is provided at a tip portion of the electron flow measuring means, and means for condensing the electron flow on the flight path to the slit or the aperture by an electric field or a magnetic field is provided. Spectroscopy device. 5. The electron spectrometer according to claim 2, wherein the electron flow measuring means includes means for deflecting the electrons in a direction different from the flight direction. 6. The method according to claim 6, wherein the electron flow measuring means uses a high voltage application, a channeltron, a channel plate, or another method.
3. The electron spectrometer according to claim 2, further comprising means for multiplying the electron flow. 7. The electron spectroscopic apparatus according to claim 6, further comprising means for changing the multiplication ability of the means for multiplying the electron flow by applying a pulse voltage or the like with time.