JP3559818B2 - Manufacturing method of nano electron source - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention utilizes a bond between molecules adsorbed on an electron source and surface atoms, and has a radius of curvature of 0.1 to several nanometers without high-temperature heating by applying a high negative voltage to the electron source. The present invention relates to a method for producing a nano electron source, which comprises producing nano projections.
[0002]
[Prior art]
A field emission electron source having a nanoprojection having a radius of curvature of several nanometers or less has the following three excellent features, and is therefore used as a new electron source in a projection electron microscope and the like. That is,
(1) Fluctuation in emission current is extremely small. Since the nanoprojection structure terminated by several atoms has a small area, the probability of molecules being adsorbed is small, the probability of shape change due to ion bombardment of residual gas is also reduced, and emission current is stable.
(2) Since the electrons converge in the emission direction region within ± 2 degrees, the efficiency of electron emission is significantly improved, and the luminance is increased.
(3) Since the electron beam is emitted from a narrow region, the coherence of the electron beam is excellent, so that it can be applied to electron beam holography and the like.
[0003]
Conventionally, a method for producing a nanoelectron source has been developed by Professor Binh of the University of Lion in France (Documents: Vu. Thien Binh, V. Semet, N. Garcia, Ultramicroscopy 58 (1995) 307-317.). FIG. 3 schematically shows a conventional method for manufacturing a nano electron source. In FIG. 3, reference numeral 1 denotes a metal needle tip having a radius of curvature of several tens of nanometers. Reference numeral 2 denotes a manufactured nanoprojection, and reference numeral 3 denotes a high-sensitivity ion detector (microchannel plate). Reference numeral 6 denotes surface atoms that have been field-evaporated from the nanoprojections.
[0004]
In the prior art, as shown in FIG. 3, a clean metal needle tip 1 is heated to a very high temperature (1500 to 2000 ° C. in the case of tungsten), and a positive high voltage is applied to the metal needle so that the surface of the metal needle is heated. Induces the diffusion of atoms and collects them at the tip. For this reason, a special heating device is required. Furthermore, at the moment when the nanoprojections 2 are completed, if the high voltage and high temperature are urgently removed, the manufactured nanoprojections 2 will be destroyed. Therefore, a highly sensitive high-sensitivity ion detector 3 for detecting the completion of the nanoprojections 2 is required.
[0005]
As shown in FIG. 3, when the nanoprojections 2 are completed, a high electric field is concentrated on the tips of the nanoprojections 2, and atoms at the tips are ionized and evaporated by the electric field. That is, a phenomenon called field evaporation occurs. The completion of the nano-projections 2 is confirmed by detecting one evaporated ion. Therefore, an expensive detector (microchanneltron) is used. Further, at the moment when the nanoprojections 2 are completed, evaporating atoms are suddenly generated without prior notice. Therefore, a special technique has been required to capture the moment when voltage and temperature are accurately removed.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a nano-electron source capable of producing nano-projections on the surface of an electron source with a simple operation without the need for heating, a special detector such as a micro-channel plate, etc. It is to provide a manufacturing method of.
[0007]
[Means for Solving the Problems]
The configuration of the present invention for achieving the above object is as follows. That is, the present invention
A first step of forming a field emission electron source tip (1) having a radius of curvature of tens to hundreds of nanometers from tungsten ;
The remaining molecules (5) are adsorbed to the field emission electron source tip (1), and the surface atoms of the field emission electron source tip (1) are easily moved by the action of the adsorbed residual molecules (5). Two steps,
And a third step of applying a high negative voltage to the surface of the field emission electron source tip (1) to form without heating the nano projections (2) having a radius of curvature of several nanometers. It has a configuration as a method of manufacturing a nano electron source.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The features of the present invention are significantly different from those of the prior art, (1) no heating is required, (2) no special detector such as a microchannel plate is required, and (3) the nano-projections can be formed by an easy operation. This is a method for producing a nano electron source, which is produced on the source surface with good reproducibility. This method of manufacturing a nanoelectron source significantly increases the applications of the nanoelectron source.
[0009]
FIG. 1 schematically shows a method for producing a nanoelectron source according to the present invention. In FIG. 1, reference numeral 1 denotes a metal needle tip having a radius of curvature of several tens of nanometers. Reference numeral 2 denotes the manufactured nanoprojections, 4 denotes a fluorescent plate, and 5 denotes a molecule adsorbed near the tip. Reference numeral 7 denotes an electron beam emitted from the nano projection 2.
[0010]
As shown in FIG. 1, the method for manufacturing a nano electron source of the present invention uses a surface contaminated by adsorption of a residual gas or the like, unlike the prior art. By appropriately selecting the adsorbed atoms and molecules, the surface atoms become remarkably mobile, and the surface atoms move even at room temperature.
[0011]
Next, unlike the prior art, when a high negative voltage is applied to obtain a field emission current, the surface atoms are attracted to the concentrated portion of the electric field at the tip of the electron source, and nanoprojections begin to form. Once the protrusions are formed, the electric field is further concentrated on the tips, and atoms are gathered, and finally, nanoprotrusions terminated with one or several atoms are formed.
[0012]
In the method for producing a nanoelectron source according to the present invention, the start of the projection formation process can be determined by an increase in the emission current, so that the completion time can be accurately determined. Further, since a large amount of emission current is observed, a highly sensitive detector unlike the related art is not required. In other words, electric field concentration occurs during the nanoprojection formation process, and when observed at the same voltage, the emission current increases by almost three orders of magnitude, and the emission direction is concentrated in a limited direction within about 2 degrees just below the electron source. Therefore, if any of these is detected, the formation of the nano-projections can be detected.
[0013]
While the conventional technology detects one ionized atom, the nanoelectron source manufacturing method of the present invention detects 100 million electrons, so that the reliability of the detection of nanoprojection formation is significantly improved. , And reproducibility is greatly improved.
[0014]
【Example】
<111> One end of a tungsten single crystal line oriented to the crystal axis is formed into a sharp needle having a radius of curvature of 100 nm by an electric field polishing method. This tip is cleaned by flash heating at 2000 ° C. or electric field evaporation within 10 ⁻⁸ Torr. The radius of curvature of this clean surface was confirmed with a field ion microscope and a field electron emission microscope. The tungsten metal needle prepared in this manner is a field emission electron source used in many electron microscopes. If this electron source is left for about half a day in a vacuum of 10 ⁻⁷ Torr, the surface of the chip becomes dirty due to adsorption of hydrogen and CO (carbon monoxide), which are main residual gases.
[0015]
When a negative bias voltage is applied to the tungsten needle of the electron source to which the molecules of the thickness of the monoatomic layer are adsorbed and the voltage is increased to 2-3 kV, electrons are emitted. When the current becomes 10 ⁻⁸ A or more, the emission current in the center direction of the emission pattern starts to increase sharply, and the emission beam pattern is concentrated only at the center. Cutting off the high voltage when the increase increased by nearly three orders of magnitude formed nanoprojections. That is, an electron beam converged in the <111> direction of tungsten is emitted. Observation of this nano-electron source with a field ion microscope reveals that a nano-projection structure terminated by one or several atoms, which is considered to be tungsten, is formed on the surface of a normal electron source.
[0016]
Due to the formation of the nano projections, the current fluctuation was extremely reduced, and the luminance was increased. FIG. 2 shows a time change of an emission current from a nanoelectron source having a nanotip structure manufactured by the method for manufacturing a nanoelectron source of the present invention. The emission current from a clean tungsten metal needle (without nanoprotrusions) of the same emission current decreases with time, whereas the current from nanoprotrusions shows a constant and stable superior property. You can see that.
[0017]
【The invention's effect】
According to the method for manufacturing a nano electron source of the present invention, a special heating device for heating the tip of a clean metal needle is not required, and a special high sensitivity and high sensitivity for detecting the completion of the nano protrusion is provided. There is no need for an ion detector, and no special skills are required to capture the moment when voltage and temperature are properly removed.
[0018]
According to the method for producing a nanoelectron source of the present invention, by utilizing a bond between a molecule adsorbed on the electron source and a surface atom and applying a high negative voltage to the electron source, 0.1 mm without high-temperature heating. Can produce nanoprotrusions having a radius of curvature of several nanometers on the surface of the electron source with good reproducibility.
[0019]
According to the method of manufacturing a nano-electron source of the present invention, 100 million electrons are detected, whereas reliability and reproducibility are significantly improved. .
[0020]
The emission current from the nano-electron source having the nano-tip structure manufactured by the method for manufacturing a nano-electron source of the present invention has extremely small time fluctuation, increases the luminance, and is stable.
[Brief description of the drawings]
FIG. 1 is a schematic view of a method for manufacturing a nano electron source according to the present invention. FIG. 2 is a time change of an emission current from a nano electron source having a nano-tip structure manufactured by the method for manufacturing a nano electron source according to the present invention. Comparison with a normal electron source without
FIG. 3 is a schematic view of a conventional method for manufacturing a nano electron source.
DESCRIPTION OF SYMBOLS 1 Metal needle tip 2 Nano projection 3 Highly sensitive ion detector 4 Fluorescent plate 5 Adsorbed molecule 6 (Electro-field evaporated from nano projection) Surface atom 7 Electron beam

Claims (1)

A first step of forming the tip of a field emission electron source having a radius of curvature of tens to hundreds of nanometers with tungsten ;
A second step of adsorbing residual molecules at the tip of the field emission electron source and easily moving surface atoms of the tip of the field emission electron source by the action of the adsorbed residual molecules;
A third step of applying a high negative voltage to the surface of the tip of the field emission electron source to form without heating a nano projection having a radius of curvature of several nanometers. .

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