JPH0616103B2 - Low speed electronic measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a technique for correcting a discharge rate, that is, a reference point, of a device that measures low-speed electrons by utilizing a gas discharge in the atmosphere.

(Prior Art) For detection of photoelectrons, thermoelectrons, and exoelectrons (hereinafter referred to as low-speed electrons) emitted from the surface of a sample, an anode is placed inside a cathode made of a conductive container opened to the atmosphere through an opening,
The first and second grids are arranged in the opening, a voltage of about 3.4 KV is applied between the cathode and the anode, and the first and second grid electrodes are always 100 V and 80 V, respectively.
A slow electronic measuring device configured to apply a voltage of the order of magnitude is used.

In this device, when the low-speed electrons emitted from the sample surface pass through the space and enter the cathode through the opening, the low-speed electrons trigger the discharge in the anode, and the anode outputs a pulse signal. While operating the counting means by this pulse signal, the potential of the first lattice electrode is raised to prevent the development of discharge, and at the same time, the second lattice electrode is lowered to a negative potential to neutralize the cations generated during the discharge. The number of low-speed electrons generated is measured while repeating the process of summing and returning to the original state.

By the way, since the low-speed electron detector is in communication with the atmosphere through the opening, atmospheric conditions such as atmospheric pressure, temperature, and humidity as shown by the solid line in FIGS. Therefore, there is a disadvantage that the discharge condition is changed and the count rate for the same anode voltage is changed significantly, resulting in a large measurement error in the measurement result.

Needless to say, such a problem is solved by detecting atmospheric conditions using a pressure sensor, a temperature sensor, a humidity sensor, etc., and adjusting the anode voltage based on the detection result, but various sensors are required. Not only that, the control amount must be determined in consideration of the difference in the degree of influence that each parameter that governs atmospheric conditions exerts on discharge conditions and the interrelationship between these, which requires a special calculation means. Cause problems.

(Object) In view of such a problem, the present invention is a reference point correction unit capable of detecting low-speed electrons with a constant sensitivity regardless of changes in atmospheric conditions without using an atmospheric condition detection sensor or a special calculation unit. An object of the present invention is to provide a low-speed electronic measuring device equipped with.

(Structure) Therefore, details of the present invention will be described below based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 denotes a container-shaped cathode which is opened to the atmosphere through an opening 1a formed in the lower portion, and which is unequal in the internal space. An anode 2 that forms an electric field, a first lattice electrode 3 that controls discharge, and a second pole electrode 4 are arranged in a vertical relationship. This anode 2 is connected to a variable voltage type high voltage generator 5 so as to generate an electric field sufficient to generate a discharge when low-speed electrons flow in, and also to an amplifier 7 via a DC blocking capacitor 6. It is connected.

The first grid electrode 3 is connected to the first pulse generator 8 and is constantly applied with a voltage of about 100 V and a voltage of about 400 V which continues Te for a certain time due to the output of the pulse signal from the amplifier 7. The second grid electrode 4 is connected to the second pulse generator 9 so that a voltage of about 80 V is normally applied, and a voltage of about −30 V that continues Te for a certain period by the output of the pulse signal from the amplifier 7 is applied. Is configured. 10 is a control circuit which is a characteristic part of the present invention,
In the state where the inflow of low-speed electrons is blocked, that is, in the atmospheric state detection mode, the output voltage of the voltage variable high voltage generator 5 is changed in one direction, and the output from the counter 11 becomes the preset count rate. At this point, the voltage scanning is stopped and the anode voltage at this time is taken in as a control parameter.In the measurement mode, the voltage when the scanning is stopped is used as a parameter to generate a constant level of discharge voltage. It is configured to be output from the device 5. Reference numeral 12 in the figure denotes a display device which processes the signal from the counter 11 and converts it into a count rate or the like for display.

Next, the operation of the apparatus configured as described above will be described based on the waveform diagram shown in FIG.

It is assumed that the current atmospheric conditions are as shown in Fig. 5 (a) (b) II.

When the sample S is placed below the cathode opening 1a and the apparatus is operated, the low-speed electrons emitted from the surface of the sample S are transferred to the anode 2
By receiving the electric field formed by the above, it sequentially passes through the second grid electrode 4 and the first grid electrode 3 and is attracted to the anode 2. In this way, when the electrons reach the vicinity of the anode 2,
The electrons are rapidly accelerated by the action of the strong electric field distributed in the vicinity of the anode, ionize the surrounding atmosphere, and cause a discharge. As a result, the anode 2 causes a rapid potential drop. This potential drop becomes a pulse signal through the DC blocking capacitor 6, is amplified by the amplifier 7, is input to the counter 11, and is displayed on the display device 12 as the generation frequency and number of low-speed electrons.

On the other hand, this pulse signal is input to the first and second pulse generators 8 and 9, and the first pulse generator 8 superimposes and outputs a pulse having a voltage of, for example, 300 V and a time width Te to output the first grid electrode 3 The potential is raised to 400 V to extinguish the discharge. Also, by outputting a pulse from the second pulse generator 9,
The potential of the second grid electrode 4 is lowered to −30 V with respect to the cathode 1, and the cations generated in the cathode 1 by the above discharge are extinguished. When the time Te has elapsed, the pulse output from the first and second pulse generators 8 and 9 is stopped, and the measuring device returns to the initial state and waits for the next inflow of low-speed electrons.

In such a state, atmospheric conditions such as atmospheric pressure, temperature, and humidity change, and conditions related to discharge such as electron mobility near the anode change, and the discharge condition changes as shown in FIG.
It is assumed that the state shown in III of (b), that is, the count rate for the same anode voltage has decreased.

Therefore, first, a state in which electrons cannot enter through the cathode opening 1a, for example, the second grid electrode 4 is set to a negative potential.

When the control circuit 10 is set to the atmospheric state detection mode at the stage where such preparations are completed, the control circuit 10 operates the voltage variable high voltage generator 5 to move the high voltage from one direction, for example, from the low voltage side. The voltage scanning is started toward the side. At the beginning of the voltage scanning, the voltage sufficient to cause the gas discharge is not applied to the anode 2, and thus the non-discharge state is maintained. When the voltage is increased in such a state, a voltage sufficient to start discharge is applied to the anode 2 and the self-sustaining discharge region is entered (curve shown by the dotted line in FIG. 5), and the amplifier 7 Outputs a pulse signal corresponding to the number of gas discharges. The counter 11 counts this pulse signal and outputs the count content to the control circuit 10. The control circuit 10 includes a counter 11
The voltage scanning of the voltage variable high voltage generator 5 is stopped at the time point when the count rate from 1 to 4 matches the set value, and at the same time, the output voltage Vd of the voltage variable high voltage generator 5 is detected. Needless to say, this voltage Vd indicates the atmospheric condition dominated by the current mutual relationships of atmospheric pressure, temperature, humidity, etc., that is, the discharge condition indicated by III in FIG. 5 (a) (b). Is.

The control circuit 10 sets the output voltage of the variable voltage high voltage generator 5 to Δ by using the output voltage Vd at the time of the discharge change as a parameter.
The discharge condition is adjusted by shifting V to the high voltage side. As a result, the discharge condition is returned to the condition before the atmospheric condition change, that is, the same condition as in FIG.
Slow electrons are detected without changing the counting rate for individual pieces.

FIG. 3 shows a second embodiment of the present invention. In the figure, reference numeral 13 is an anode disposed inside a container-shaped cathode 1, and a conductive wire is formed in a loop shape, which will be described later. It receives electric power from the anode temperature control circuit 15 and is heated by Joule heat. The anode 13 is connected to the variable voltage high voltage generator 14 so as to generate an electric field sufficient to cause discharge when low-speed electrons flow in, and also to the amplifier 7 via the DC blocking capacitor 6. It is connected. Reference numeral 15 is an anode temperature control circuit which is a characteristic part of the present invention, and is set to a temperature sufficient to generate a constant level of discharge with the voltage at the time of reaching a preset count rate in the atmospheric condition detection mode as a parameter. It is configured to supply heating power.

Next, the operation of the apparatus thus configured will be described based on the waveform chart shown in FIG.

Atmospheric conditions such as atmospheric pressure, temperature, and humidity change to change the conditions related to discharge such as electron mobility in the vicinity of the anode 13, and the discharge condition is indicated by II in FIG. 5 (a) (b). It is assumed that the state has changed to the state shown in FIG. 3, that is, the state in which the count rate decreases.

Therefore, first, a state in which electrons cannot enter through the cathode opening 1a, for example, the second grid electrode 4 is set to a negative potential.

Upon completion of such preparation, the anode temperature control circuit 15
Is set to the atmospheric condition detection mode, the voltage scanning of the output voltage of the variable voltage high voltage generator 14 is started from the low voltage side to the high voltage side. When the anode voltage is increased in this state, the anode 13 enters the self-sustaining discharge area as soon as the voltage sufficient to start the discharge is applied, and the pulse signal corresponding to the number of gas discharges is output from the amplifier 7. Output. The counter 11 counts this pulse signal and outputs the count content to the anode temperature control circuit 15. Anode temperature control circuit 15
When the count rate from the counter 11 matches the set value, the voltage scanning of the voltage variable high voltage generator 14 is stopped and the output voltage Vd 'is detected. At the same time, the heating power to the anode is increased by using the output voltage Vd 'at the time of the discharge change as a parameter, and the temperature of the anode 13 is shifted to the high temperature side by ΔT. This raises the temperature of the gas near the anode 13 and increases the mobility of electrons. As a result, the discharge condition is the state before the atmospheric condition change, that is, FIG. 5 (a).
The condition is returned to the condition indicated by II in (b), and thereafter, low-speed electrons are detected without changing the count rate for one low-speed electron, that is, the detection sensitivity. If the ambient temperature rises or falls too much, once the heating power to the anode is returned to the initial state and then the atmospheric state is detected, measurement error will be reduced as much as possible. Can be made smaller.

Although the voltage scanning is performed from the low voltage side in the above-described embodiment, the voltage variable type high voltage is determined based on the anode voltage at the time when the counting rate is reduced to the set value by performing the scanning from the high voltage side. It is apparent that the same effect can be obtained by controlling the output voltage of the voltage generator 5 or the heating power from the anode temperature control circuit 15.

Further, in the above-described embodiment, the discharge state detection in the atmospheric state detection mode is performed by changing the count rate, but it is based on the peak value of the pulse signal output from the amplifier 7 and the magnitude of the anode load current. It goes without saying that it can be detected by

Further, in the above-described embodiment, the current is passed through the anode to directly heat the anode. However, the same effect can be obtained by disposing a heater near the anode to indirectly heat the anode.

Further, in the above-described embodiment, the measurement mode and the atmospheric condition detection mode are manually selected, but by using a timer or the like, it is possible to automatically switch between the modes at regular intervals.

Further, in the above-described embodiment, the state in which the intrusion of low-speed electrons is blocked, that is, the state in which low-speed electrons are zero is used as the calibration reference, but an object that emits a known amount of energy rays such as electron beams is used, and this energy ray is used. Needless to say, even if the counting rate based on is adjusted so as to be constant, the same effect is obtained.

(Effect) As described above, according to the present invention, the anode voltage at the time of low-speed electron measurement or the voltage at the time when the discharge state is changed by changing the anode voltage in one direction in the state where low-speed electrons do not enter Since the anode temperature is set, low-speed electrons can always be detected with a constant sensitivity without using special atmospheric condition detecting means or arithmetic means.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, and FIG.
FIG. 3 is a waveform diagram showing the operation of the above-mentioned device, FIG. 3 is a configuration diagram of the device showing another embodiment of the present invention, FIG. 4 is a waveform diagram showing the operation of the device shown in FIG. Fig. 5 (a) (b)
FIG. 4 is a characteristic diagram showing the relationship between the atmospheric condition and the count rate in the low-speed electronic measuring device. 1 ... Cathode, 2, 13 ... Anode 3, 4 ... Lattice electrode

Claims (2)

[Claims] 1. A low-speed electron detector comprising a container-shaped cathode communicating with the atmosphere and having an inlet for low-speed electrons formed therein, and an anode arranged inside the cathode, and at least the anode. A variable voltage type high voltage generating means for outputting a voltage sufficient to cause discharge, and a discharge state of the anode by changing the output voltage of the variable voltage type high voltage generating means in one direction without the inflow of low-speed electrons. And a control unit that detects the voltage of the anode when the low speed electron is detected and applies the voltage to the anode when the low speed electron is detected. 2. A low-speed electron detector comprising a container-shaped cathode communicating with the atmosphere and having a low-speed electron inflow port formed therein, and an anode arranged inside the cathode, and at least the anode. A variable voltage type high voltage generating means for outputting a voltage sufficient to generate a discharge, a means for heating the anode, and a unidirectional change in the output of the variable voltage type high voltage generating means without the inflow of low-speed electrons. And a control means for controlling the temperature of the heating means by the output voltage in which the discharge state of the anode is changed.