JPH0627854B2 - Low speed electronic measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for measuring low-speed electrons by utilizing gas discharge in the atmosphere, and more particularly to a technique for improving detection sensitivity.

(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 grid electrodes are arranged in the opening, and a voltage of about 3.4 KV is applied between the cathode and the anode.
And the second grid electrode are always 100 V and 80 V, respectively.
A low-speed electronic measuring device configured to apply a voltage of the order of V is used.

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

By the way, the electrons emitted from the sample are usually once attached to oxygen molecules in the atmosphere and then attracted to the cathode by the positive electric field generated by the lattice electrode or the anode, so that the moving speed becomes extremely slow, and as a result, Not only does the ratio of the number of generated electrons that are scattered outside the cathode due to the influence of the external environment and contribute to the discharge decrease and the sensitivity decreases, but it also takes time to move from the sample surface to the anode and the response speed increases. There was an inconvenience that it was low.

In order to solve such a problem, for example, it is conceivable to increase the potential of the lattice electrode to electrically accelerate the oxygen ions to which the slow electrons are attached in the cathode direction. There is a problem that the ratio of ions trapped in the electrode becomes large, which not only causes a limit to improve the counting rate, but also affects the electric field strength distribution in the grid electrode tube and changes the measurement conditions. .

(Purpose) The present invention has been made in view of such problems, and an object of the present invention is to enhance the collection rate of low-speed electrons emitted from a sample as much as possible, to improve detection sensitivity and response speed. It is to provide a low-speed electronic measuring device capable of improving

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

1 and 2 show one embodiment of the present invention,
In the figure, reference numeral 1 is a conductive container body which is opened to the atmosphere through an opening 1a, and is divided into two upper and lower regions by an electric insulating material 2, and a cathode 3 is formed on the side of the opening 1a. In the cathode 3, the anode 4 that forms an unequal electric field is on the center line, and the first lattice electrode 7 and the second pole electrode 8 that control the discharge coaxially through the cylindrical supports 5 and 6 are arranged vertically. It is arranged so that.

On the other hand, in the space above the container body 1, a load resistor 10 for supplying an output voltage from the high voltage generator 9 to the anode 4, a capacitor 11 for cutting a DC component, and a preamplifier 12 for amplifying an output signal from the load resistor 10. Is housed. 13, 13
Is a suction port and the insulator 2 above the anode 4 so as to suck the air in the space surrounded by the support 6 of the second grid electrode 8.
Is formed by making a through hole in it, and the other end is connected to a suction pump 15 by a pipe 14.

A counter 16 counts the pulse signals from the preamplifier 12 and displays the count value on the display device 17. Reference numeral 18 is a first pulse generator, the output terminal of which is connected to the first grid electrode 7 and outputs a voltage of about 100 V at all times, or a voltage of about 400 V which continues Te for a certain time by the pulse signal from the counter 16. It is a thing. Reference numeral 19 is a second pulse generator, whose output terminal is connected to the second grid electrode 8 and which normally outputs a voltage of about 80 V, and a pulse signal from the counter 16 outputs a voltage of about -30 V for continuing Te for a certain time. To do. Reference numeral 20 in the figure is an electrical insulating material for drawing out the lead wires.

Next, the operation of the apparatus thus configured will be described with reference to FIG.

When the device is activated, the pump 15 causes the suction ports 13, 13
To suck air in the inner space of the support 5 of the first grid electrode 7 to generate an air flow F from the outside of the cathode opening 1a toward the anode 4. This air flow F passes along the anode 4 and discharges the water present near the anode 3 to the outside.

In such a state, when the sample S is arranged below the cathode opening 1a and energy is applied to the surface of the sample S by ultraviolet rays or the like, the sample S emits slow electrons from the surface.
The low-speed electrons once attach to gas molecules around the sample, are forcibly drawn into the opening 1a by riding on the air flow F in the vicinity thereof, and then the action of the electric field formed by the anode 4 and the lattice electrodes 7 and 8 And the air flow F in the support 5 rapidly causes the anode 4
Be drawn to. In this way, the electrons attached to the gas molecules and carried to the vicinity of the anode 4 are rapidly accelerated by the action of the strong electric field distributed near the anode 4, and ionize the surrounding atmosphere to discharge. Raise. This makes the anode 4
Causes a sharp potential drop. This potential drop becomes a pulse signal via the capacitor 11, is amplified by the amplifier 12, is input to the counter 16, and is displayed on the display device 17 as the generation frequency and number of low-speed electrons.

On the other hand, this pulse signal is generated by the first and second pulse generators 1
8 and 19, the first pulse generator 18 outputs a pulse having a voltage of, for example, 300 V and a time width Te to superimpose and output the potential of the first grid electrode 7 to 400 V to stop the discharge, and during the discharge. The cations generated near the anode are recombined with the electrons to neutralize them. Further, a pulse is output from the second pulse generator 19 to lower the potential of the second grid electrode 8 to -30 V with respect to the cathode 1, and cations generated during discharge are collided with the second grid to neutralize, It prevents cations from jumping out of the opening 1a and impacting the surface of the sample S, and prevents electrons from adhering oxygen molecules into the lattice electrode 8.

In parallel with this, the ions generated in the vicinity of the anode 4 are discharged to the outside of the cathode 3 from the suction ports 13, 13 by the air flow F, so that the impact on the surface of the sample S is reduced as much as possible, and the discharge is suppressed. It will shorten the disappearance time. When time Te has elapsed from the start of discharge, the first and second pulse generators 1
The pulse output from 7 and 18 is stopped, and the measuring device returns to the initial state and waits for the next inflow of low-speed electrons.

Example 1 A sample S is a detector having a cathode having an opening with a diameter of 10 mm.
And the potentials of the first and second grid electrodes and the anode were controlled as in the same step as above, and the suction capacity of the suction pump was changed to examine the counting rate. However, as shown in FIG. 4, the count rate increased in proportion to the increase in the suction amount.

On the other hand, for comparison, the pump was stopped, the inter-electrode voltage was kept constant, and the count rate was measured for the same sample while changing the initial potential of the second grid electrode while maintaining the inter-electrode voltage constant. As shown in the figure, the count rate increases in proportion to the increase in the potential of the second grid electrode, but the extension of the count rate decreases from the vicinity of the potential of the second grid electrode reaching 200 V, and the saturation tendency tends to occur. Began to show.

From this, it was found that forming the air flow from the cathode opening toward the anode had a great effect on the improvement of the counting rate.

[Example 2] The above detector having an opening with a diameter of 10 mm was arranged at a distance of 10 mm with respect to the sample S, and a 3 /
When the change in the count rate from the time of irradiation with ultraviolet rays was examined in a state where air was sucked in at a rate of minutes, the count rate reached a steady value 30 seconds after the irradiation, as shown in FIG.

On the other hand, for comparison, the same measurement was performed with the potential of the second grid electrode set to a high level without suctioning air, and as shown in FIG. Reached

From this, it was confirmed that forming the air flow from the cathode opening toward the anode not only improves the counting rate but also significantly improves the response speed.

In this embodiment, through holes are formed in the electric insulator 2 that divides the container body 1 to form the suction ports 13 and 13 to suck air in the internal space of the first grid electrode support 5. However, even if a through hole is formed in the first grid electrode support body to provide a suction port, or a through hole is formed in the insulator and suction is performed through the upper space of the container body 1. It is clear that the same effect is achieved.

FIG. 8 shows a second embodiment of the present invention, in which ejection ports 21, 21 communicating with the space formed by the first grid electrode support 5 and the second grid electrode support 6 are formed. The pipe 22 is connected to the dry gas source 23 to supply the dry gas to the vicinity of the first grid electrode 7.

In this embodiment, when the device is activated, the pump 15
Sucks the air in the internal space of the support 5 of the first grid electrode 7 through the suction ports 13 and 13 to generate the air flow F from the outside of the cathode opening 1a toward the anode 3, and The emitted low-speed electrons once attach to the gas molecules around the sample and are forcibly drawn into the opening 1a by riding on the air flow F in the vicinity thereof. At the same time, the dry gases f, f ejected from the gas ejection ports 21, 21 are mixed with the air flow F from the cathode opening 1 a in the vicinity of the first grid electrode 7 and head toward the anode 4. As a result, the humidity in the space surrounded by the first grid electrode support 5 is reduced, the water existing in the vicinity of the anode 4 is removed, the discharge condition becomes constant, and the count rate is stabilized. Further, by using a discharge-assisting gas such as argon gas as the dry gas, it is possible to stabilize the discharge conditions and improve the discharge efficiency, that is, the detection sensitivity.

FIG. 9 shows a third embodiment of the present invention, in which reference numeral 31 is a conductive container body which is open to the atmosphere through an opening 31a, and which is electrically insulating material 32 in two upper and lower regions. The cathode 33 is formed on the side of the opening 31a by division. Cathode 3
The anode 34 that forms an unequal electric field is placed on the center line in 3
Further, a grid electrode 36 that controls discharge is coaxially arranged via a tubular support 35.

37, 37 are suction ports, which are formed by forming through holes in the insulator 32 above the anode 34 so as to suck the air in the space surrounded by the support 35 of the lattice electrode 36, and the other end It is connected to the suction pump 15 by a pipe 38.

A counter 16 counts the pulse signals from the preamplifier 12 and displays the count value on the display device 17. Reference numeral 39 is a pulse generator, the output terminal of which is connected to the grid electrode 36 and which constantly supplies a voltage of about 100V.
In addition, the pulse signal from the counter 16 outputs a voltage of about 400 V that continues Te for a certain time.

In this embodiment, when the device is activated, the pump 15
Sucks air in the internal space of the support 5 of the grid electrode 36 from the suction ports 37, 37 to generate an air flow F from the outside of the cathode opening 31a toward the anode 34. This air flow F
Passes along the anode 34 and discharges the water existing near the surface of the anode 34 to the outside.

In such a state, the low-speed electrons emitted from the surface of the sample S once attach to the gas molecules around the sample, ride on the air flow F in the vicinity thereof and are forcibly drawn into the opening 31a, and then the anode 34. The action of the electric field formed by the grid electrode 36 and the air flow F causes the air flow F to rapidly draw it toward the anode 34. In this manner, the gas molecules are attached to the anode 4
The electrons carried to the vicinity of are rapidly accelerated by the action of the strong electric field distributed in the vicinity of the anode 4, and ionize the surrounding atmosphere to cause discharge. As a result, the anode 34 causes a rapid potential drop. This potential drop becomes a pulse signal via the capacitor 11, is amplified by the amplifier 12, is input to the counter 16, and is displayed on the display device 17 as the generation frequency and number of low-speed electrons.

On the other hand, this pulse signal is input to the pulse generator 39,
The voltage from the pulse generator 39 is, for example, 300 V and the time width T
By superimposing and outputting the pulse of e, the potential of the first grid electrode 7 is set to 4
The voltage is raised to 00 V, the cations generated near the anode 34 due to the above-mentioned discharge are extinguished, and the discharge is quickly stopped.

On the other hand, the cations generated during discharge during the period until disappearance are
The air flow F near the anode 4 causes the air to be discharged from the suction ports 37, 37 to the outside of the cathode 33, so that the surface of the sample S cannot be impacted. In this way, when the time Te has elapsed from the start of the discharge, the pulse output from the pulse generator 39 is stopped and the measuring device returns to the initial state.

By the way, in the ion erasing step, the low-speed electrons continuously emitted from the surface of the sample S may be dissipated to the outside of the cathode 33 by the action of the positive electric field of the lattice electrode and the action of the air flow F. Since it cannot be formed, it exists near the opening 31a. Therefore, at the same time the device returns to the initial state,
The low-speed electrons in the vicinity of the opening 31a are immediately attracted by the air flow F and immediately move to the vicinity of the anode 34 to induce the next discharge without any play time.

According to this embodiment, not only the second grid electrode facing the cathode opening and the second pulse generator (FIG. 18) are not required, but the device can be simplified, and the use of the second grid electrode is also possible. It is possible to speed up the measurement cycle by eliminating the repulsion of low-speed electrons due to the action of the negative electric field in the discharge stopping step.

(Effects) As described above, according to the present invention, the air flow from the cathode opening toward the anode is formed. Therefore, the low-speed electrons emitted from the sample are collected on the anode side by the air flow. Not only can the count rate be improved, but the response speed can be improved by increasing the moving speed from the sample surface to the anode. It can be removed and the discharge conditions can be maintained constant, and the measurement conditions can be stabilized.

Further, the cations generated by the discharge can be quickly discharged to the outside of the cathode by the air flow to prevent the collision with the sample, and the potential control of the second grid electrode at the time of the discharge stop operation, by extension, this grid electrode It becomes unnecessary and simplification of the structure becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus showing an embodiment of the present invention, and FIG.
FIG. 4 is a sectional view of an insulating material portion of the same apparatus, FIG. 3 is a waveform diagram showing the operation of the same apparatus, FIG. 4 is a relationship diagram between suction amount and count rate in the same apparatus, and FIG. Fig. 6 is a diagram showing the relationship between the electric potential and the counting rate, Fig. 6 is a response characteristic diagram in the Fig. 1 device, and Fig. 7 is a response characteristic diagram in the conventional device.
Each of the drawings is a block diagram of an apparatus showing another embodiment of the present invention. 3 ... Cathode, 4 ... Anode 7, 8 ... Lattice electrode, 13 ... Suction port 15 ... Suction pump

Claims (1)

[Claims] 1. A container-shaped cathode having at one end an opening through which low-speed electrons flow, an anode disposed inside the cathode and supplied with a voltage sufficient to cause discharge when low-speed electrons flow in, A low speed electronic measuring device comprising means for generating an air flow from the opening towards the anode.