JPH0627058A - Electron spectroscopy and apparatus therefor - Google Patents

Abstract

PURPOSE:To realize highly efficient high resolution electron spectroscopy by irradiating a sample with pulse X-ray or ultrashort wave pulse ultraviolet ray, flying emitted electrons by a predetermined distance, and then measuring the flight time. CONSTITUTION:Upon irradiation of a sample 1 with pulse X-ray projected from a pulse X-ray projector 2, pulsating electron beam (e) is emitted from the surface of the sample 1. The electron beam (e) is subjected to energy regulation through a grid 3 and passed through a long flight path 4 thus converting energy spectrum of electron on a slit 6 into temporal variation of electron flow. Furthermore, electronic lenses 13 are disposed on the opposite sides of the flight path 5 in order to collect electrons emitted from the sample 1 through the lenses 13 within the flight path 4 thus enhancing electron capture rate. Electrons (e) are then accelerated in an accelerating field 7 and deflected in a deflecting field 8 to the direction perpendicular to the flying direction and then temporal variation of electron flow is converted into spacial variation thus detecting energy spectrum of electron easily through a one-dimensional array. Furthermore, electron energy distribution converted into spacial distribution is amplified through a channel plate 9 and optically converted through a fluorescent screen 10 to be observed by means of a camera 12 through an optical lens 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron spectroscope for analyzing energy of electrons generated in a pulse shape.

[0002]

2. Description of the Related Art The energy distribution of electrons emitted from a substance by irradiation with light, X-rays, electrons, etc. contains information about the state of the substance, and Auger electron spectroscopy etc. generated by electron beam irradiation etc. Ultraviolet photoelectron spectroscopy (UPS) and soft X-ray photoelectron spectroscopy (XPS), which measure photoelectrons generated by UV or X-ray irradiation, are important analysis methods essential for studying material states, especially surface states. Has become.

Conventionally, many electron spectroscopes using a deceleration electric field have been used in the initial stage, and at present, a cylindrical mirror type energy analyzer (CMA) is most often used (reference: 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 through a narrow entrance slit between cylindrical electrodes to which an electrostatic field is applied, only electrons having a certain energy are focused on a measuring instrument through a narrow exit slit. Using the principle of
It is possible to know the electron energy distribution by changing the magnitude of the electrostatic field, but it is possible to capture the electrons emitted from the sample in a wide solid angle even under the high resolution measurement of 0.25%. The sensitivity of CMA is higher than that of other analyzers.

However, in the case of CMA, only electrons of a specific energy are measured at one set voltage. For example, when measuring a high-precision 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. Radiation damage to the sample is also a problem.

Therefore, an electrostatic hemispherical energy analyzer as shown in FIG. 2 has been developed to increase the measurement 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 focused on the exit surface E, but the focusing position depends on the electron energy. Therefore, by observing the spatial distribution of the electron beam condensed on the emission surface with the one-dimensional array or the two-dimensional image detector D, the electrons in a relatively wide energy range are measured at one time. According to the method, energy analysis can be performed at a speed of about 200 times that of CMA, for example.

[0007]

However, these conventional electron spectroscopic apparatuses generate from a sample which is constantly irradiated with ultraviolet rays or X-rays 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 electrons that are emitted and, in addition, can simultaneously handle multipoint data. Even in the electrostatic hemisphere analyzer described above, the energy range that can be measured at one time is only about 10%.

Further, in the electrostatic hemispherical analyzer, in order to obtain a certain energy resolution, 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 low.

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

However, even with these high-intensity pulse radiation sources, the peak output is high but the average output is not so high. On the other hand, in the conventional electron spectroscope designed for the steady irradiation source, the average output is high. It is only important that the high peak power of the high intensity pulsed source cannot be measured.

Therefore, in the present invention, by developing an electron spectroscopic method with high detection efficiency and an apparatus therefor utilizing the characteristics of the high-intensity pulsed line source as described above, a new observation method such as observation of a high-speed phenomenon of the surface state of a sample The purpose is to enable the development of application fields.

[0012]

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

Further, in the present invention, a means for irradiating pulse X-rays or pulse ultra-short wavelength ultraviolet rays and a flight path for causing electrons emitted from the sample to fly a predetermined distance when the sample is irradiated with the pulse X-rays or pulse ultra-short wavelength ultraviolet rays. And an electron spectroscopic device comprising electron flow measuring means for measuring the flight time.

That is, when an electron flies over a certain distance, its flight time depends on the energy of the electron. Therefore, if the electron flow is observed at a place sufficiently distant from the electron source, the electron energy is separated from the time change. Then, by recording all this time change, the generated electrons can be measured without being wasted, and the efficiency of the measurement becomes extremely high.

In the present invention, as the pulsed X-ray irradiating means, an ultrashort pulse laser generated plasma, an X-ray laser or the like can be used, and as the irradiating means for pulsed ultrashort wavelength ultraviolet rays, a harmonic of an ultrashort pulse laser is used. 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 difference of flight to be observed. For example, an electron of 300 eV flies a distance of 1 meter in 100 nanoseconds (one tenth of a million seconds), but at an area 1 meter from the electron source, the energy spectrum of an electron of 300 eV on average is 1 / 100th. In order to measure with the energy accuracy of 2, the electron flow measurement requires a time resolution of 2 nanoseconds, and the generation of electrons needs to have a pulse width shorter than that. If pulse X-rays obtained in recent years are used, it is possible to easily generate electrons with a pulse width of this level.

Further, 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.

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

The electrons emitted from the substance upon irradiation with X-rays or the like are distributed over a wide solid angle. However, a lens with an electric field or a magnetic field is provided on the flight path so that the electrons emitted over a wide solid angle are far away. The electron trapping rate can be increased by condensing in a slit shape or a spot shape on the electron flow measuring device which is installed separately.

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

That is, 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 such as applying a time-swept electric field, it is possible to convert the time-of-flight distribution into a spatial distribution. For example, a television camera or an image detector can be used and data processing becomes easy.

Further, as described above, the energy resolution can be kept high by sweeping and deflecting the spatially limited electron flow through the slits or pinholes.

Further, by accelerating the electrons at a high speed by applying a high voltage, using a channeltron, a channel plate, etc., or by combining them, the electron flow is multiplied to increase 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, but the acceleration of electrons due to the application of a high voltage as described above is an energy region in which the energy dependence of sensitivity is not great. There is an advantage that data processing can be facilitated by accelerating electrons with, but by making the duration of its amplifying ability extremely short and synchronizing it with the pulsed electron flow, further signal pairing is possible. The noise ratio can be improved.

[0025]

According to the present invention, the electrons emitted from the sample by pulse excitation such as ultrashort pulse X-rays can be separated with extremely high detection efficiency and high resolution. Excitation such as X-ray is used as a measuring 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 The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention, in which 1 is a sample, 2 is a pulsed X-ray irradiator such as plasma produced by an ultrashort pulse laser, 3 is a deceleration grit, and 4 is set with a predetermined distance. An electron flow flight path 5 is an electron flow measuring instrument.

In this embodiment, the electron flow measuring instrument 5 is provided with a slit 6 at the tip thereof, an acceleration electric field 7 and a deflection electric field 8 behind the slit 6, and a channel behind the deflection 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, from the pulse X-ray irradiator 2 to the pulse X
When the sample 1 is irradiated with a line, a pulsed electron beam e is generated from the surface of the sample 1. After the electron energy of this electron beam e is adjusted by the grit 3, the electron beam e is passed through the long flight path 4, whereby the energy spectrum of the electrons is converted into the 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 slits 4 by using the electron lenses 13 to collect electrons. It is designed to increase

Next, after producing a sufficient flight time difference, the signal is multiplied by accelerating with the acceleration electric field 7. Further, by applying a deflecting electric field 8 that changes with time at high speed to deflect the electrons e in a direction orthogonal to the flight direction, the time change of the electron flow is converted into a spatial change, and a one-dimensional array or a two-dimensional image is obtained. A detector is used to facilitate the recording of the electron energy spectrum.

The electron energy distribution converted into the spatial distribution is further amplified by the channel plate 9 or the like, and then the fluorescent plate 10
After converting to light with, use the optical lens 11 etc. to the camera 12
Observe at.

In this case, the signal-to-noise ratio can be improved by applying a pulse voltage 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 drawings]

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

FIG. 2 is an explanatory view of the principle of a conventionally used electrostatic hemispherical energy analyzer.

[Explanation of symbols]

1 sample 2 pulse X-ray irradiator 3 deceleration grit 4 electron flow flight path 5 electron flow measuring instrument 6 slit 7 acceleration 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 electrostatic hemispherical energy analyzer two spherical electrodes S entrance slit E exit surface D one-dimensional array or two-dimensional image detector α slit angular width incident on S

Claims (7)

[Claims] 1. An electron spectroscopy method, which comprises irradiating a sample with pulsed X-rays or pulsed ultrashort wavelength ultraviolet rays, causing electrons emitted from the sample to fly for a predetermined distance, and measuring the flight time. 2. A means for irradiating pulse X-rays to pulse ultra-short wavelength ultraviolet rays, a flight path for flying electrons emitted from the sample for a predetermined distance when the sample is irradiated with the pulse X-rays to pulse ultra-short wavelength ultraviolet rays, and its flight. An electron spectroscope comprising an electron flow measuring means for measuring time. 3. An electron spectroscopic apparatus according to claim 2, further comprising means for decelerating or accelerating the electron flow in the flight path. 4. A device according to claim 2, wherein a slit or aperture is provided at the tip of the electron flow measuring means, and means for condensing the electron flow in the flight path on the slit or aperture by an electric field or a magnetic field. An electron spectroscopic device according to the above item. 5. The electron spectroscopic apparatus according to claim 2, wherein the electron flow measuring means comprises means for deflecting the electrons in a direction different from the flight direction thereof. 6. The electron spectroscopic apparatus according to claim 2, wherein the electron flow measuring means comprises means for multiplying the electron flow by electron acceleration, channeltron, channel plate or other methods. 7. An electron spectrometer according to claim 6, further comprising means for temporally changing the capacity of the means for multiplying the electron flow.