JP2936529B2 - Optical STM device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injecting electrons into a very small region of a material or a structure embedded in a material, detecting light emission caused by the injected electrons, and measuring the intensity or spectrum of the light. The present invention relates to an optical STM device that enables observing the characteristics of a very small region of the material or the structure with high accuracy and high resolution by measuring the spatial distribution image of the light emission according to the detection position.

[0002]

2. Description of the Related Art Heretofore, in this type of apparatus, an optical element such as a lens or a reflecting mirror installed independently of a probe has been used as a mechanism for collecting observation light. Because these optical elements can be easily installed completely separate from the short hand,
These optical elements did not affect the electrical characteristics and driving function of the probe.

However, optical STM (Structured)
With the advancement of the performance of the Test Model device, in order to improve the light collection efficiency, a probe (hereinafter, referred to as a probe) having both a function of collecting light and a function of supplying a tunnel current.
A "collective STM probe" has been developed.

In this light-collecting STM probe, the optical fiber is shaped so as to have a high light-collecting efficiency, and the surface is conductively processed so that a stable tunnel current can flow. The focusing STM probe requires a transmission optical fiber for guiding light from the probe to a spectroscope or the like.

[0005] In the optical STM apparatus, the sample may be cooled to an extremely low temperature in order to increase the emission intensity or to clearly measure various characteristics of the sample. When the sample is cooled, the surface of the sample is contaminated with extraneous matter. Therefore, it is necessary to keep all of the sample, the probe, and the like in an extremely high vacuum.

[0006] By adding cooling means and vacuum evacuation means, the environmental space conditions around the probe have become narrower and tighter. Therefore, the optical fiber has been guided and inserted linearly in consideration of maintenance workability. By the way, in the STM, it is necessary to largely move the probe two-dimensionally back and forth or right and left in accordance with a change of the sample, a change of the measurement position on the sample, and a change of the probe.

At this time, if the optical fiber is connected in a straight line, the optical fiber has a considerable elasticity in a bent state, so that the probe and the probe driving mechanism (mainly a piezo element) , Etc.), the bending stress of the optical fiber greatly changes, so that accurate probe driving becomes impossible. Therefore, in the conventional apparatus, this problem has been avoided by abandoning the probe moving function and moving the sample while fixing the probe.

[0008]

However, in the conventional method of moving a sample, the following problems become apparent. That is, since the measurement position is adjusted by moving the sample stage on which the sample is mounted, the sample stage requires various levels of position adjustment mechanisms from coarse adjustment to fine adjustment, and the structure becomes large and complicated. This is a problem.

Considering the structure for achieving the degree of vacuum required for measurement and the cooling of the sample, it must be said that the use of such a sample stage is difficult. Accordingly, there has been a strong demand for a fiber installation specification which enables long-distance linear reciprocation of the probe and hardly applies stress to the probe.

Further, it has been experimentally revealed that an optical fiber generally considered to be an insulator has a certain degree of conductivity, and a leak current flowing through this optical fiber has an insignificant effect on tunnel current measurement. Found to give. Therefore, a means for completely removing the leak current flowing through the optical fiber is required.

This is unnecessary in the conventional metal STM probe, and is a problem peculiar to an optical STM device having both functions of detecting light and supplying a tunnel current. When these are installed in an extremely high vacuum, it is difficult to directly fix the fiber to the final installation position from the outside. Therefore, means for accurately guiding the fiber from the outside of the apparatus to the final installation position is also required.

As described above, the inventor of the present invention has made the prior art light S
In the optical fiber mounting means used in the TM device, excessive mechanical stress is generated in the probe and the probe driving mechanism, and this stress changes greatly with the movement of the probe. I found a problem that I couldn't do it.

The main technical problems to be solved by the present invention are as listed below. A first object of the present invention is to provide an optical STM device that enables long-distance linear reciprocal movement of a probe without impairing high-precision probe driving.

A second object of the present invention is to provide an optical STM device capable of eliminating leak current flowing through a fiber as much as possible.

[0015] A third object of the present invention is to provide an optical STM apparatus in which stress is not easily applied to a moving probe.

A fourth object of the present invention is to provide an optical STM device having means for accurately guiding an optical fiber from the outside of the device to a final installation position.

A fifth object of the present invention is to provide an optical STM device that can be observed in a sealed cooling atmosphere.

[0018] A sixth object of the present invention is to provide an optical STM device that can be observed in a sealed vacuum atmosphere.

Other objects of the present invention will become apparent from the description and drawings, particularly from the appended claims.

[0020]

The object of the present invention can be attained by adopting the following novel features and methods of the present invention. That is, a first feature of the present invention is that a sealed measuring chamber in which a light-transmitting and conductive probe for collecting observation light from a sample placed on an internal sample stage at the tip of the needle is installed. In an optical STM device in which the free end of an optical fiber connected to a measuring device is guided and inserted into a room from outside, and the observation light is receivably centered on the base end of the probe, the probe is movable. While the intermediate portion of the optical fiber is elastically bent and deformed within a predetermined radius of curvature region, while the base end portion is fixedly held and the tip end portion is held movably in the axial direction. Light ST
M device.

A second aspect of the present invention is an optical STM apparatus in which the optical fiber according to the first aspect is internally held along an elbow tube axis centered on the degree of bending deformation of the intermediate portion.

According to a third aspect of the present invention, in the optical fiber according to the second aspect, the base end side of the optical fiber is fixedly held at the axis of the fixed anchor spacer fitted in the fiber outlet at the outer end of the elbow tube. This is an optical STM device drawn out.

A fourth feature of the present invention is the optical fiber according to the second or third feature, wherein the optical fiber sticks to the axis of a conical convex movable anchor spacer having a distal end slidably fitted in the inner end of the elbow tube. This is an optical STM device held.

According to a fifth feature of the present invention, the elbow tube according to the second, third or fourth feature is characterized in that the elbow tube is provided with a fiber associated with the axial sliding of the conical convex movable anchor spacer integrated with the movement of the probe. An optical STM device having an inner diameter that does not cause contact due to elastic strain deformation.

The sixth feature of the present invention is the fourth or fifth aspect.
An optical STM device in which the probe driving mechanism according to the above feature is characterized in that a conical concave centering seat that is slidably fitted inside the inner end of the elbow tube and mates with the conical convex movable anchor spacer is male and female. It is.

A seventh feature of the present invention is that the first, second, and
The probe driving mechanism according to the third, fourth, fifth or sixth feature is an optical STM device which is a piezo element.

An eighth feature of the present invention is that the fourth, fifth, and fifth aspects of the present invention are described below.
An optical STM device in which the conical convex movable anchor spacer and the conical concave centering seat in the sixth or seventh aspect are formed of an electrically insulating material.

A ninth feature of the present invention is that the first, second, and
The sealed measurement chamber according to the third, fourth, fifth, sixth, seventh, or eighth feature is an optical STM device including a cooling unit therein.

According to a tenth feature of the present invention, the sealed measurement chamber in the first, second, third, fourth, fifth, sixth, seventh, eighth or ninth feature is characterized by that An optical STM device that communicates with the room.

[0030]

According to the present invention, since the above-mentioned novel means is employed, even if the optical fiber is deformed by the probe moving mechanism, stress is not easily applied, and therefore, accurate long-distance linear reciprocal movement of the probe can be achieved. Can be. In addition, by forming the movable anchor spacer and the centering seat for male and female fitting with an electrically insulating material, it is possible to minimize leakage current through the optical fiber.

The stress in the optical fiber generated by the movement of the probe is dispersed into a vertical stress which coincides with the moving direction of the probe and a shear stress which is orthogonal to the moving direction by bending the intermediate portion to a required curvature. By exhibiting elasticity and lateral elasticity, elastic deformation of the fiber can be easily promoted, and adverse effects on the probe and the probe moving mechanism can be avoided as much as possible.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory longitudinal sectional view for explaining the structure of this embodiment. In the figure, A is the optical STM device of this embodiment, B is a sealed measuring chamber, 1 is a probe, 2 is a probe driving mechanism using a piezo element or the like, 3 is a sample on the sample stage 3a, 4 is a cooling means. , 5
Is a vacuum container.

6 is an optical fiber for optical transmission, 7 is an elbow tube,
Reference numeral 8a denotes a frustoconical conical convex movable anchor spacer in which the tip of the optical fiber 6 for optical transmission penetrates the axis and is slidably fitted in the inner end of the elbow tube 7; A fixed anchor spacer 9 which is fitted in the mouth 7a and which is drawn through the optical transmission optical fiber 6 at the axis thereof is protruded from the probe driving mechanism 2 and is slidably fitted in the elbow tube 7 and is conical. The mortar-shaped conical concave centering seats 10 and 11 are male and female fitted to the convex movable anchor spacer 8a.

The proximal end 1a of the probe 1 is fixed to the probe drive mechanism 2, and the distal end 1b of the probe 1 is installed so as to freely contact the sample 3 on the sample stage 3a. The probe 1, the probe drive mechanism 2 and the sample 3 are provided with a cooling means 4 lined in a sealed measurement chamber B.
And can be cooled to a predetermined low temperature at the time of measurement.

The probe 1, the probe drive mechanism 2, the sample 3, and the cooling means 4 are used to prevent contamination of the surface.
All are housed in a vacuum vessel 5 kept in ultra-vacuum by a vacuum exhaust device (not shown) of vacuum exhaust means communicating with the inside. The surplus space around the probe driving mechanism 2 is very narrow and substantially sealed to improve cooling efficiency and reduce sample surface contamination.

The distal end 1a of the probe 1 has the distal end of the optical transmission fiber 6 aligned with and in contact with the base 1a. The light is guided to light processing means (not shown). At the distal end of the optical fiber 6 for light transmission, a heavy, axially symmetric, conical-convex movable anchor spacer 8a is fixedly attached to the axis thereof. That is, the feature of the present embodiment is that the intermediate portion of the optical fiber for optical transmission 6 is bent with a large radius of curvature.

The characteristic of the present embodiment, that is, the standard of the radius of curvature will be described below. If the curvature is too small, a large shearing force is applied to the optical fiber 6 at the holding portions near both ends of the optical fiber 6, and adverse effects such as breakage of the optical fiber 6 and distortion of the probe driving mechanism 2 occur.

On the other hand, if the radius of curvature is too large (the shape of the optical fiber 6 is substantially linear), the amount of change in the mechanical normal stress of the optical fiber 6 accompanying the axial movement of the probe 1 becomes large, which is undesirable. Effect cannot be obtained. Therefore, the radius of curvature of the optical fiber 6 is determined so that the shearing force applied to both ends of the holding of the optical fiber 6 is substantially constant within the range of the vertical reciprocating movement of the probe 1 required in the optical STM apparatus A. At such a radius of curvature, the material is dispersed and deformed into longitudinal elasticity and lateral elasticity, and the absolute value of the shearing force is small.

Usually, in the optical fiber 6 having a diameter of 400 μm,
This radius of curvature is about 10 to 20 cm. Thus, the practical advantage of the present embodiment is that the radius of curvature of the optical fiber 6 at which the desired effect is exhibited is not strict, and there is a certain wide tolerance. In such a bent state,
The entire optical fiber 6 does not form a circular arc, and a linear portion 6b is formed at the distal end and the proximal end connected to the intermediate circular arc portion 6a having the above-mentioned curvature.

The straight portion 6b may be used in a state where the length of the straight portion 6b is about the radius of the circular arc portion 6a or more. However, if the straight portion 6b is too long, the bending and swinging of the optical fiber 6 will increase, and unnecessary mechanical vibration will increase. If a long straight portion 6b is needed, a support member is installed.

When the optical fiber 6 can be directly hand-operated at the time of mounting, it is relatively easy to install the above-mentioned curved optical fiber 6, but in the optical STM apparatus A, the space in which the optical fiber 6 is to be introduced. Around the cooling means 4 and the vacuum vessel 5
Therefore, it is extremely difficult to hold the optical fiber 6 that has been elastically bent and deformed.

Therefore, an elbow pipe 7 for guiding the optical fiber 6 is provided. The elbow tube 7 is bent along the curvature of the optical fiber 6 and has such a diameter that the inner diameter of the optical fiber 6 does not contact the inner wall even when the inserted optical fiber 6 is elastically deformed when the probe 1 moves. ing. This elbow tube 7
From the position where the tip of the optical fiber 6 is aligned with and in contact with the base end 1a of the probe 1, it passes through the upper part of the sealed measuring chamber B with the cooling means 4 and penetrates the sealing members 10 and 11 and extends to the outside of the vacuum vessel 5. I have.

As shown in FIG. 1, it is natural that vacuum sealing means 12 for holding a vacuum is attached to the outer end of the elbow tube 7. At the inner end of the elbow tube 7, a conical convex movable anchor spacer 8 penetrating the tip of the optical fiber 6 is provided.
A conical concave centering seat 9, which is a mortar-shaped jig that fits both males and females, is slidably fitted inside.

When the optical fiber 6 is inserted up to the inner end of the elbow tube 7, the conical convex movable anchor spacer 8 a at the tip of the optical fiber 6 is fitted by the conical concave centering seat 9, and the hand is held from the outside. Without the addition, it is possible to perform centering in which the center axis of the optical fiber 6 automatically matches the center axis of the elbow tube 7.

By manufacturing the conical convex movable anchor spacer 8a and the conical concave centering seat 9 from an electrically insulating material, it is possible to cut off the leak current passing through the optical fiber 6. As the electrically insulating material, any material such as ceramics may be used as long as the material does not contaminate the vacuum and is not damaged by cooling.

Further, the shapes of the movable anchor spacer 8a and the centering seat 9 are not limited to those shown in FIG. 1, and the center of the tip of the optical fiber 6 with respect to the base 1a of the probe 1 is adjusted. If it is a shape that guarantees contact, the shape may be reversed, for example, a plurality of conical holes may be provided on the centering seat 9 side and conical protrusions may be provided on the movable anchor spacer 8a side for joining. Even if a cross or a radial groove is provided on the side 9 and a cross or a radial peak is provided on the movable anchor spacer 8a side, there is no particular problem.

Note that the tunnel current to the probe 1 and the drive current to the probe drive mechanism 2 are supplied through wires (not shown) or through the elbow tube 7 as conductive.

[0048]

As described above, according to the present invention, by bending the optical fiber for optical transmission into an arc shape, it is possible to move the probe up and down linearly for a long distance without impairing high-precision probe drive. Is possible.

Further, since the movable anchor spacer and the centering seat which are fitted to each other are made of an electrically insulating material, a leak current leaking from the optical fiber which is not an insulating material in a strict sense is eliminated. In addition, it exhibits excellent usefulness and utility, such as being observable in a cooling sealed atmosphere or a vacuum sealed atmosphere.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view illustrating the structure of an embodiment of the present invention.

[Explanation of symbols]

 A: Optical STM device B: Sealed measurement chamber 1: Probe 1a: Base end 1b: Needle tip 2: Probe drive mechanism 3: Sample 3a: Sample stage 4: Cooling means 5: Vacuum container 6: Optical fiber for optical transmission 6a ... Arc part 6b ... Linear part 7 ... Elbow tube 8a ... Conical convex movable anchor spacer 8b ... Fixed anchor spacer 9 ... Conical concave centering seat 10,11 ... Sealing member 12 ... Vacuum sealing means

Claims (10)

(57) [Claims] 1. A sealed measuring chamber having a light-transmitting and conductive probe for collecting observation light from a sample placed on an internal sample stage at the tip of the needle, and connecting to a measuring instrument from outside. Light S which guides and penetrates the free end of the optical fiber thus inserted into the room and aligns and adjoins the observation light at the base end of the probe so as to be receivable.
In the TM device, the probe is movably attached to a probe drive mechanism, and the intermediate portion of the optical fiber is elastically bent and deformed within a predetermined radius of curvature region, while a base end portion is fixedly held and the distal end portion is fixed. An optical STM device, wherein the optical STM device is held movably in the axial direction. 2. The optical STM apparatus according to claim 1, wherein the optical fiber is internally held along an elbow tube axis centered on the degree of bending deformation of the intermediate portion. 3. The optical fiber according to claim 2, wherein the optical fiber is pulled out by holding and holding the base end side to the axis of the fixed anchor spacer fitted in the fiber outlet at the outer end of the elbow tube. STM device. 4. An optical fiber according to claim 2, wherein the optical fiber is fixedly fitted to the axis of a conical convex movable anchor spacer whose tip end is slidably fitted to the inner end of the elbow tube. STM device. 5. The elbow tube according to claim 1, wherein the inner diameter of the elbow tube does not cause contact due to elastic strain deformation of the optical fiber caused by axial sliding of the conical convex movable anchor spacer integral with the movement of the probe. Item 5. The optical STM device according to item 2, 3 or 4. 6. The probe driving mechanism is characterized in that a conical concave centering seat that is slidably fitted on the inner end of the elbow tube and mates with a conical convex movable anchor spacer is provided. The optical STM device according to claim 4 or 5, wherein 7. The optical system according to claim 1, wherein the probe driving mechanism is a piezo element.
TM device. 8. The optical STM apparatus according to claim 4, wherein the conical convex movable anchor spacer and the conical concave centering seat are formed of an electrically insulating material. 9. An optical STM apparatus according to claim 1, wherein said sealed measuring chamber is provided with cooling means therein. 10. The sealed measurement chamber communicates with the vacuum exhaust means and the interior of the chamber.
10. The optical STM device according to 6, 7, 8 or 9.