JPS5949065A - Diffusing feed type electron beam source - Google Patents

Abstract

PURPOSE:To perform easily the electron radiation with angle limit without introducing oxygen gas, etc. from outside, by using an oxide of titanium, hafnium, niobium, magnesium or cerium or a solid solution or a fused mixture of above- mentioned elements and their oxides to a feed source. CONSTITUTION:First, a tungsten wire of 0.1-0.15mm. diameter is spot-welded at the tip of a V-shaped tungsten (W) heat generator 1 having 0.1-0.15 diameter. The tip of the generator 1 is shapened by electrolytic polishing to obtain an electron radiator 2. Then a titanium oxide (TiO2, etc.) or the mixture powder of titanium (Ti) and TiO2 is attached to a connecting part of the generator 1 to the radiator 2 or around the generator 1 to obtain a quasi-feed source 4'. Then the generator 1 is energized and heated under vacuum or in an Ar gas atmosphere, etc. Thus the source 4' is fused instantly to obtain a feed source 4. The same effect can be obtained if a mere fused mixture of titanium and titanium oxide is used to the source 4.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a thermal field emission cathode (thermal field emission cathode).
dEmission Cathode (hereinafter referred to as TEF Cathode).

[Prior art]

Field emission (1+1 field emission) is a phenomenon in which when a strong electric field of about 100 to 4 V/cm is applied to the emitter surface, electrons are emitted from the cathode surface due to a tunnel effect. In electric field emission, a sword-shaped tip with a radius of curvature of approximately one angstrom at the tip is used as a cathode in order to obtain a strong electric field. Electric field radiation can be roughly divided into electric field radiation when the chip temperature is near room temperature.
d Emission, hereafter referred to as 'r Jy) and'
There is I"FE.The former, 1"E, is a method of keeping the temperature of the emitter tip at room temperature and applying a strong electric field to draw out the emission.It is mainly used in transmission electron microscopes and scanning electron microscopes. It's sharp. In order to operate the FE stably, the space where the emitter is located must be maintained at a vacuum below lQ -1011Nor r in order to reduce gas adsorption to the emitter tip and eliminate damage to the emitter due to ion bombardment. The emission current for stable operation is 1
It is 0μ8 or less. On the other hand, 1'li'' E is a method of drawing out C emissions by applying a strong electric field while heating the emitter tip to a temperature range that does not generate thermoelectrons. It is possible to obtain an emission current of about 100 μA with 1, and its applications include scanning-type gun-powder self-imitation bells, transparent-type Ichiko-ken microscopes, branching devices such as Auger electron analyzers, and electron beam lithography equipment. is wide.

Now, 'l'I"E can be classified into the following two types depending on the method. One is build-up, in which a specific crystal plane is heated to a high temperature and the emitter is heated in a specific gas atmosphere. When a strong electric field is applied to the tip, the surface atoms move to specific crystal planes and rearrange to form protrusions 4, and the local radius of curvature becomes small.This method is called a build amplifier. For example, in a vacuum system with many 07, C02, 11□0 gas components, Tankus-Ten (W) (100
) surface is built up using the method proposed by Shira, 10
-” [1750~18 in 02 gas atmosphere of about [orr]
By heating the emitter to 50K and adsorbing zirconium (Zr) to the tip of the emitter, Emin/Yon 111;
This makes it possible to limit the angular distribution of the flow. A suction state of Zr OW is formed at the emitter tip, and W(100
) surface's work function decreases between 26 and 2.8 eVt. A similar effect was obtained with titanium (1゛l), unilam (1-1f).
), niobium (Nb), thorium ('l”h), magj (
/lum (IVl,,g) and cerium (Ce).

Regarding the post-processing method of the above TPE, an example of a diffusion replenishment type electron beam source using zirconium (Zr) as an adsorbent will be explained with reference to FIG. The diffused replenishment type electron beam source is composed of a heating element 1 and a replenishment source 3 that stores Zr, which is an adsorbent to the electron emitter 2.

In this case, the Zr supply source 3 is obtained by heat-treating a coated Zn2 powder. In the operating state, the heating element 1 is heated by electricity, and ZR, which is an adsorbent, is diffused on the surface by heating from the replenishment source 3, and the electron emitter 2 is heated to 300~150.
A strong electric field is applied to the sword-shaped electron emitter 2 while it is heated to 0C, and 10'-8 to 10-"l is placed in a vacuum container.
When the 02 gas of 'orr is introduced, electron emission is angularly restricted only to the (100) crystal orientation of the electron emitter 2 made of single crystal tungsten (W). That is, the work relationship on the W (100) plane is about 2.6 to 2.8 eV, which is lower than about 4.5 eV for W and about 3.5 eV for Zr, and electron emission is likely to occur, and the radiation angle Due to the reduced electron emission, gas emission from the anode section is reduced, resulting in a stable and stable electron emission capability.

By the way, in the above-mentioned conventional diffusion replenishment type electron source, since the adsorbent is only Zr, the operating temperature is relatively high, and there is a possibility that undesirable thermal and electron radiation may be mixed in. Therefore, there are problems in that IV' is brittle during heat treatment or easily contaminated with impurities. To solve these problems, zirconium (Zr), titanium ('ll
A diffusion-replenishment type field emission cathode using a metal replenishment source made of a metal string such as hafnium (Hf) is also available.This cathode has a lower operating temperature even with the same Zr replenishment source ( 1,250 to 1,450 tl?), and the required oxygen gas partial pressure is now approximately 10"" Torr or less.In the case of supplementary Tr, there is no need to introduce oxygen gas during operation. Although it has become possible to draw current stably, it may be necessary to introduce oxygen scum during the initial stage of installation in actual equipment.

As mentioned above, the diffuse replenishment type i' F B is a powerful electron radiation source, but in order to emit electrons with a reduced radiation angle in the diffuse replenishment type 'I' F E, it is necessary to At the tip of the metal replenishment valve 3, it is necessary to maintain a monoatomic layer adsorption state between the metal adsorbent (for example, Zr or Ti) and oxygen. In conventional diffusion replenishment type electron beam sources, a single metal (for example 7.r) is used as the replenishment source 3.
However, in order to maintain the angle-limited electron emission for a long time, O gas of less than 10-"I" orr had to be introduced, depending on the metal used and its operating temperature. Ta.

[Purpose of the invention]

An object of the present invention is to provide a diffusion replenishment type electron beam source that can stably emit electrons with a reduced radiation angle for a long period of time without introducing O2 gas during operation.

[Summary of the invention]

Diffusion replenishment type electron beam source 3''1 consists of an electron emitter with a sword-shaped tip, a heating element that heats the electron emitter, an adsorbent that adsorbs to the electron emitter, and a supply source that stores it. In order to emit electrons with a reduced radiation angle, it is necessary to form a monoatomic layer adsorption state of adsorbent and oxygen at the tip of the electron emitter.

The electron emitter mainly has a diameter of 0 in the axial direction (100).
．． Single crystal tungsten (W, ) of 1 to 0.15 TTm is used. It is desirable that the heating element has low electrical resistance, high high temperature strength, and low reactivity with the supply source. Mainly tungsten (W), molybuti 7 (MO),
V: = ram (Re), tantalum (Ta) and alloys thereof, or alloys of the above metals with supply sources may be used.

As the heating element, an O wire with a diameter of 0.1 to 0.5 tnm or a plate-shaped one with a thickness of 02 to 0.02 mm is used. The present invention uses zirconium (Zr) and titanium 7 as supply sources.
('ri)%ノs7. Jmu (Hf), Niobium (Nb)
, oxides such as thorium (Th), magnesium (Mg), cerium (Ce), or Zr, T1, Ilf,
It is characterized by using a solid solution or a molten mixture of Nb, 'l'h, Mg, Ce, and their oxides, and attaching it to the above-mentioned heating element or the contact between the heating element and the electron emitter.

In conventional diffusion replenishment type electron beam sources, for example, Zr or Hf metal is used as a replenishment source, and during operation, Zr or Hf is supplied to the tip of the electron emitter by thermal diffusion, and oxygen gas is introduced from the outside to adjust the radiation angle. It emitted electrons that were reduced in size. On the other hand, in the present invention, as shown in the phase diagram of T1 and TlO2 shown in FIG. 2, a solid solution of Ti and oxygen,
Currently, a molten mixture of Illi and 1゛102 or titanium oxide, etc. is used as a replenishment source, and in the operating state, titanium and oxygen are simultaneously supplied to the tip of the electron emitter, allowing emission without introducing oxygen gas etc. from the outside. This makes it possible to emit electrons with a reduced angle.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 The first example of the diffusion replenishment type electron beam source according to the present invention was
This will be explained with reference to Figures (a) and (b). First, a tungsten wire with a diameter of 0.1 to 0.15 m is spot-welded to the tip of a tungsten (W)-equipped heating element 1 with a diameter of 0.1 to 0.15 wm formed in a figure 7 shape, and the tip is connected to potassium hydroxide. (KOH)
The electron emitter 2 is produced by sharpening it by electropolishing with an aqueous solution or the like. Next, titanium oxide (e.g. 'r
i o2) or titanium (Tl) and titanium oxide <
A mixed powder of T lot > is adhered to the grooves of the heating element 1 and the electron emitter 2 as shown in FIG. 3(a), or around the heating element 1 as shown in FIG. 3(b). Next, the heating element 1 is energized and heated in a vacuum or an argon (Ar) gas atmosphere to instantaneously melt the additional supply source 4' to create the supply source 4. As for the components of the supply source 4, the ratio of 0/Ti is 0.
Any solid solution of titanium and oxygen in the range of 2 to 2 may be used. According to the phase diagram of '■゛1-TlO2 in Figure 2, in the region of the ratio 0/'I'i, Tio2, Tl2
Although there are titanium oxide states such as O3.1 and 10, either state may be used as the replenishment source 4 of the present invention. Similar effects can be obtained even if the raw material supply source 4 is simply a molten mixture of titanium and titanium oxide.

In the diffusion replenishment type electron beam in this embodiment, when the electron emitter 2 and the replenishment source 4 are heated to 900C to 1500tr by heating the heating element 1 with electricity in an ultra-high vacuum, the electron beam becomes sharp in the form of a needle due to thermal diffusion. supply source 4 up to the tip of the electron emitter 2
When titanium (T) and oxygen are replenished and a high voltage is applied between the electron emitter 2 and the opposing anode in this state, tungsten (T) is replenished without introducing oxygen gas etc. from the outside.
The work function of the (100) crystal plane of the electron emitter 1 made of W) is lowered, and electron emission whose angle is restricted to the (100) plane orientation can be obtained.

In addition, as the supply source 4, the o/zr ratio is 0.2 to 2.
A solid solution or a molten mixture of zirconium (Zr) and zirconium oxide may be used, and 0/Tb, 0/Nb
, 0/Hf, 0/Mg, 0/Ce ratio is 0.2 to 20
Thorium ('l'h) and thorium oxide, hafnium (Hf) and hafnium oxide, and niobium (Nb) are mixed in proportions.
) and niobium oxide, cerium (Ce) and cerium oxide, electron radiation with a reduced radiation angle at a temperature of 900 to 1500 C can be similarly obtained. I was able to do it.

Embodiment 2 Another embodiment of the diffusion replenishment type electron beam source according to the present invention will be described with reference to FIG. 3(C). In this embodiment, a ribbon or wire made of titanium oxide or a molten mixture of titanium and titanium oxide is prepared in advance and used as the additional supply source 4' by wrapping it around the heating element 1. Reinforcement source 4' Ribbon or Gentleman, 0/T! The ratio is 0.2~
It can be produced by melting and mixing raw materials of titanium and titanium oxide weighed at a blending ratio of 2 in, for example, an alcohol gas atmosphere, and then rapidly cooling the mixture using an ultra-quenching method. Next, in a vacuum or the like, heat generating element 1 wrapped with semi-replenishing coil 4'
The supplementary supply source 4' is melted by instantaneously heating to C to form the supplementary supply source 4. A diffused replenishment type electron beam source provided with a replenishment source 4 formed by this method has an electron emitter 2 of 900 to 150 (
By heating to I', electron radiation with a reduced radiation angle could be obtained without introducing oxygen gas or the like from the outside.

As a supply source 4, solid solutions or molten mixtures of zirconium and zirconium oxide, niobium and dibutylene oxide, )-fnium and hafnium oxide, thorium and thorium oxide, magi-sium and magnonium oxide, and cerium and cerium oxide are used. A similar effect could be obtained by using

Embodiment 3 FIG. 3(d) shows another embodiment of the present invention. That is,
Titanium oxide powder is applied in advance to the long side of a titanium ribbon made of sintered titanium wire, and an additional supply source 4' sintered at 800 to 1500 C is wrapped around the heating element 1. Next, the heating element 1 is heated to 1,600 to 1,900 U to melt the preparation source 4' and form the supply source 4. Similarly, zirconium oxide, niobium oxide, niobium oxide, thorium oxide, magnesium oxide, and cerium oxide are applied to the surface of zirconium, niobium, ferrite, thorium, magnesium, cerium, or foil to increase replenishment sources. 4' and the diffused replenishment type electron source that formed the replenishment source 4,
We were able to easily obtain angle-limited electron emission without introducing oxygen gas from the outside.

Example 4 Another embodiment of the present invention will be described with reference to FIG. 3(e).

In this embodiment, titanium powder, titanium wire,
Uses titanium ribbon. First, apply titanium powder around the heating element 1 or wrap titanium wire or titanium ribbon around the heating element 1, and then
The supplementary supply source 4' is melted by electrically heating the heating element 1 in a container into which oxygen gas is introduced at 7 Torr, or by indirectly heating the heating element 1 by installing a coil heater or the like around the heating element 1. A replenishment source 4 is formed by absorbing and solidly dissolving. When the diffusion replenishment type quantum beam source created according to this example is operated at 900 to 1500 tr in an ultra-high vacuum container, it is possible to obtain electron radiation whose radiation angle is reduced in the (100) plane orientation of the tungsten electron emitter 2. can.

Furthermore, the same effect could be obtained by using powder, wire, or foil of zirconium, niobium, hafnium, thorium, red sea bream, cerium, etc. as the supplementary supply source 4'.

Example 5 Another embodiment of the present invention will be described with reference to FIG. 3(f).

This embodiment is characterized by a composite replenishment source 5 that integrates a heating element for heating the electron emitter 2 and a replenishment source. The composite source 5 consists of wires or ribbons or plates formed from solid solutions or molten mixtures of titanium, zirconium, niobium, hafnium, thorium, magnesium, cerium and their oxides. The wire, ribbon, or plate of the composite supply source 5 can be made by, for example, melting and mixing a mixture of titanium and titanium oxide in an argon atmosphere or the like, and then using an ultra-quenching method. A tungsten (W) electron emitter 2 is spot-welded to the tip of the figure 7-shaped composite replenishment source 5, and the tip of the electron emitter 2 is made sharp by electrolytic polishing or the like, thereby producing a diffused replenishment type quantum beam source. In the operating state, titanium and oxygen were supplied to the tip of the electron emitter 2 by heating the composite replenisher 5 with electricity, making it possible to obtain electron emission whose angle was restricted to the (100) plane orientation of tungsten.

Example 6 Another embodiment of the present invention will be described with reference to FIG. 2(g).

- First, a tungsten wire 2' is spot-welded to the tip of the figure 7-shaped heating element 1 as an electron emitter, and then titanium, zirconium, niobium, hafnium, thorium, maggotium, cerium, etc. An evaporation source 6 made of 1M or foil such as
- In a vacuum container introduced with 8'l"orr, the evaporation source 6 is energized and heated to evaporate the heating element 1 and the tungsten wire 2'.
The material of the evaporation source 6 is deposited around the evaporation source 6 to form an additional supply source 4'. The contents of, for example, titanium and oxygen in the supplementary supply source 4' can be arbitrarily controlled by the evaporation rate of the evaporation source 6 and the pressure of oxygen gas during deposition. Next, the tip of the tungsten wire is sharpened by electrolytic polishing or the like to form an electron emitter 2.

The tip of the electron emitter 2 may be sharpened before forming the supplementary supply source 4'. During actual operation, heating element 1
The additional supply source 4' is once melted by heating with electricity to form the supply source 4, and the wettability with the electron emitter 2 and the heating element 1 is improved. Also in the diffusion replenishment type quantum beam source created by the above procedure, as in the case of Examples 1 to 5, 9
By operating at 00 to 15 ooc, it was possible to easily obtain electron emission angle-limited to the tungsten (100) plane orientation.

〔Effect of the invention〕

As described above, the diffusion replenishment type quantum beam source of the present invention is capable of obtaining angle-limited electron emission by forming an adsorption state of a monoatomic layer of an adsorbent and oxygen at the tip of an electron emitter having a sharp tip. In addition, titanium, zirconium, hafnium,
Niobium, thorium, magnesium, cerium oxides or titanium, zirconium, hafnium, niobium,
A diffusion-supplemented electron beam that uses a solid solution or molten mixture of thorium, magnesium, cerium, and their oxides to easily emit electrons with a limited angle without introducing oxygen gas from the outside. I was able to offer some advice.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional diffusion replenishment type quantum beam source, FIG. 2 is an equilibrium state diagram of Ti and TiO2, and FIG. 3 is a detailed explanatory diagram of the present invention. DESCRIPTION OF SYMBOLS 1... Heating element, 2... Electron emitter, 3... Metal supply source, 4... Supply source, 4'... Increased supply source, 5...
Composite supply source, te1 fig.%z fig.to7 cho1)
(cji ((t)°′°(a2
(3)

Claims (1)

[Claims] 1. Diffusion consisting of an electron emitter with a needle-like tip, a heating element that heats the electron emitter, an adsorbent to the electron emitter, and a supply source that stores the adsorbent. In a supplementary electron beam source, oxides of titanium, zirconium, hafnium, niobium, thorium, magnesium, or cerium, or titanium, zirconium, hafnium, niobium,
A diffusion replenishment type electron beam source characterized by using a solid solution or molten mixture of thorium, red sea bream, ium, or cerium and its oxide. 2. The diffusion replenishment type Hiroko wire according to claim 1, wherein the replenishment source is titanium oxide or a solid solution or molten mixture of titanium oxide and titanium, with a ratio of 0/T1 in the range of 0.2 to 2. source. 3. The diffusion replenishment type electron beam according to claim 1, wherein the replenishment source is zirconium oxide, or a solid solution or molten mixture of zirconium oxide and zirconium, with a 0/Zr ratio in the range of 0.2 to 2. source. 4. The supply source mentioned above has a ratio of 0/Hf of 0.2 to 2.
2. The diffusion assisted electron beam source according to claim 1, which is hafnium oxide or a solid solution or molten mixture of hafnium oxide and hafnium. 5. The diffusion replenishment type electron beam according to claim 1, wherein the replenishment source is niobium oxide or a solid solution or molten mixture of niobium oxide and niobium with a 0/Nb ratio in the range of 0.2 to 2. source. 6. The diffusion replenishment type electron beam according to claim 1, wherein the replenishment source is thorium oxide or a solid mixture of thorium oxide and thorium with an o/'rh ratio in the range of 0.2 to 2. Ryo. 7. The diffusion replenishment type according to claim 1, wherein the replenishment source is a solid solution or molten mixture of magnesium oxide or magi-sium oxide and Makufu7ium in which the ratio of 07Mg is in the range of 0.2 to 2. Electron beam source. 8. The diffusion replenishment type electron according to claim 1, wherein the replenishment source is cerium oxide having an O/Ce ratio in the range of 0.2 to 2, or a solid bath or molten mixture of cerium oxide and cerium. Shingen.