JPH09196937A - Photon scanning tunneling microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photon scanning tunneling microscope of higher resolving power and higher condensing efficiency by providing a scattering light condensing part to the base part of a probe over the almost entire periphery thereof. SOLUTION: A scattering light sampling means 18 consists of a flat-headed optical fiber 60 and the pointed probe 64 provided at the almost central part of the flat-headed surface 62 of the fiber 60 and a gold film 21 is formed on the surface of the probe 64. The flat-headed surface 62 constitutes a scattering light condensing part provided over the entire periphery of the base part of the probe 64. Next, when the probe 64 penetrates into an evanescent light field 16, scattering light is generated from the leading end part of the probe 64 and the greater part of the scattering light L advances toward the flat-headed surface 62 of the fiber 60 and the light penetrating into the fiber 60 from the flat-headed surface 62 is sent to a notch filter as it is. The scattering light generated by the penetration of the probe 64 into the evanescent light field is highly efficiently caught by the flat-headed surface 62.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photon scanning tunneling microscope, and more particularly to improvement of a scattered light focusing mechanism.

[0002]

2. Description of the Related Art A general microscope allows non-contact and destruction of a sample to observe a microscopic minimal portion, and by connecting a spectroscopic analyzer or the like, not only the shape and structure of an observation object but also its It is also possible to analyze components,
It is applied in various fields. However, a general optical microscope cannot observe an object having a wavelength smaller than the wavelength of light, and its resolution is limited. On the other hand, with an electron microscope or the like, the resolution can be greatly improved, but operation in the atmosphere or in a solution is extremely difficult, and a high-resolution microscope such as an electron microscope is not always satisfactory especially in the field of handling biological samples. It didn't go.

On the other hand, in recent years, a photon scanning tunneling microscope based on a principle different from that of a general optical microscope or electron microscope has been developed and its application is expected.
This photon scanning tunneling microscope detects so-called evanescent light. That is, when a small sample to be measured is placed on a flat substrate and light is incident from the back surface of the substrate at an angle such that total internal reflection occurs, all propagating light is reflected, but the surface of the substrate and the object to be measured is A surface wave called evanescent light is generated in the vicinity. This surface wave is localized in a region around the surface of the object within a distance within the wavelength of light.

Therefore, by inserting a sharp probe into the field of evanescent light to scatter the evanescent light and measuring the scattered light intensity, the distance between the probe tip and the surface of the object to be measured can be defined. . Therefore, by scanning the probe while keeping the intensity of the scattered light constant, the probe tip position accurately reflects the irregularities on the surface of the object to be measured, and the probe tip is in the evanescent light field. Since it exists only and is not in contact with the object to be measured, it can be observed that it is non-contact, non-destructive with respect to the sample and smaller than the wavelength value of light.

Conventionally, such a probe and a scattered light collecting mechanism as shown in FIG. 1 have been generally used. In the figure, the sample 10 to be measured is placed on an inverted triangular total reflection prism 12, and laser light 14 is incident on the total reflection prism 12 and is totally reflected at the boundary surface between the sample 10 and the prism 12. ing. In this state, the evanescent light 16 is applied to the surface side (upper side in the figure) of the sample 10.
Has occurred.

When the tip of the pointed optical fiber probe 18 is inserted into the field of the evanescent light, the evanescent light 16 is scattered by the tip of the fiber probe 18, and a part of the scattered light 20 enters the fiber probe 18, The light is guided to the detection mechanism described later. FIG. 2 shows the correlation between the evanescent light intensity and the distance from the sample surface. As is clear from the figure, the two have a close relationship, and the evanescent light intensity is kept constant. By scanning the surface of the sample 10 while moving the tip of the fiber probe 18 up and down, it is possible to accurately grasp the unevenness of the sample 10 without contacting the sample 10.

By the way, in order to improve the resolution of the photon scanning microscope, it is necessary to form smaller minute apertures. However, it is not easy to form a minute opening on a plane. Therefore, as shown in FIG. 1, a pointed probe 18 is formed, and a mask 21 is formed on the probe 18 with a metal film or the like to make the tip 18a a minute opening. There is. However,
When the probe and the scattered light condensing mechanism as shown in FIG. 1 are used, there is a drawback that the wave guide efficiency is poor because the probe tip is less than the wavelength and the total converging amount is small because the converging angle is small. .

On the other hand, a so-called apertureless type probe has also been developed. FIG. 3 shows a conceptual diagram thereof. The parts corresponding to those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The probe 18 shown in the figure is a sharpened tip of a metal or a semiconductor. When the metal probe 18 enters the evanescent light field 16 on the surface of the sample 10, scattered light is generated and the scattered light 20 is collected. It is condensed by the optical lens 24 and detected by the detector 26.

When such an apertureless probe is used, compared to the case where the probe shown in FIG. 1 is used, the loss of scattered light due to waveguide is small, a high SN ratio can be realized, and the surroundings of the probe can be realized. Since no metal coating is required, high resolution can be easily achieved.

[0010]

However, even in the conventional photon scanning tunneling microscope using the above-mentioned apertureless probe, the condensing efficiency is still insufficient, and the condensing lens is used to disperse scattered light from the side. Since the light is condensed through the light, scattered light in all directions cannot be collected, and there is a problem that shadows are formed.

Particularly, when not only the shape information of the sample is obtained from the scattered light intensity but also the component information of the sample to be measured is obtained, the light collection efficiency has a very important meaning.
There has been a demand for the development of a better photon scanning tunneling microscope. The present invention has been made in view of the above prior art, and an object thereof is to provide a photon scanning tunneling microscope having a higher resolution and a higher scattered light collecting efficiency.

[0012]

In order to achieve the above object, in a photon scanning tunneling microscope according to the present invention, a scattered light collecting means collects scattered light provided over substantially the entire circumference of the probe base. It is characterized by having a light section. In the present invention, the scattered light collecting means comprises an optical fiber and a pointed probe provided substantially at the center of the end face of the optical fiber, and a metal coating is formed on the pointed probe surface. Is preferred.

Further, the microscope according to the present invention comprises a separating means for separating the scattered light collected by the scattered light collecting means into Rayleigh light and Raman light, and a sample to be measured from the Rayleigh light intensity separated by the separating means. It is preferable to include separation information acquisition means for acquiring separation information between the surface and the probe, and spectrum information acquisition means for separating Raman light separated by the separation means to obtain Raman spectral spectrum information. In the microscope, the scattered light sampling means scans the surface of the sample to be measured in the X and Y axis directions.
It is preferable to provide a Y-axis scanning means so that the separation information and the spectrum information at each measurement site on the surface of the sample to be measured can be simultaneously acquired.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. In the next embodiment, the photon scanning tunneling microscope is used so that the shape measurement and the component measurement of the sample to be measured can be simultaneously performed. That is, as in the case of general scattered light, the scattered light 20 is Rayleigh light which is scattered light with no frequency change, and incident light in an amount equal to the fluctuation frequency of the scattering system depending on the components of the sample 10. Raman light having a frequency deviated from the frequency of is included. Therefore, the inventors of the present invention focused on both the Rayleigh light and the Raman light, and detected the distance between the tip of the fiber probe 18 and the sample surface by using the Rayleigh light that does not include the component information of the measured sample 10 but has a relatively high intensity. Used, sample 1
The Raman light having the component information of 0 was collected as the spectrum information for the component analysis.

FIG. 3 shows a schematic structure of a photon scanning tunneling microscope 30 according to an embodiment of the present invention.
A microscope 30 shown in the figure includes scattered light collecting means 18, a separating means 32 including a notch filter for separating scattered light obtained through the scattered light collecting means 18 into Rayleigh light and Raman light, and the scattered light collecting means. The tip of the means 18 is moved vertically (Z
A separation information acquisition unit 34 for controlling in the axial direction), a spectrum information acquisition unit 36 for separating the Raman light separated by the separation unit 32 to obtain spectrum information, an X, Y axis scanning unit 38, and a display unit 40. Including.

Then, the scattered light collecting means 18 has X,
The Y-axis scanning means 38 scans the sample surface in the XY directions (directions parallel to the sample surface). Further, the separation information acquisition means 3
4 includes a Rayleigh photodetector 42 and a Z-axis scanner 44,
The Rayleigh light separated by the notch filter 32 is detected by a detector 42, and based on the output, the Z-axis scanner 44 controls the position of the scattered light sampling means 18 in the Z-axis direction so that the Rayleigh light intensity becomes constant. To do. Further, the spectrum information acquisition means 36 includes a spectroscope 46, a Raman light detector 48 for detecting spectroscopic Raman light, and a spectrum storage 50 for storing the Raman light spectrum information based on the output of the detector 48. Including.

The Raman light separated by the notch filter 32 is detected by the detector 48 and the spectrum memory 50 together with the wavelength information obtained from the spectroscope 46.
Is stored. The display means 40 displays the X and Y coordinates of each measurement point from the X and Y axis scanning means 38 and the Z axis scanning means 3 respectively.
The height information of the sample surface at each measurement point is obtained from 4 and the spectrum information or component information at each measurement point is obtained from the spectrum information acquisition means 36 and displayed. As described above, according to the photon scanning tunneling microscope 30 according to the present embodiment, the scattered light collected by the one scattered light collecting means 18 is separated into the Rayleigh light and the Raman light by the separating means 32, and the sample surface is detected from the Rayleigh light. It is possible to simultaneously obtain the height information of the component and the component information at each measurement point on the sample surface from the Raman light.

By the way, when the scattered light is used by separating the Rayleigh light and the Raman light as in this embodiment, the light collection efficiency of the scattered light has a great influence on the measurement accuracy. In particular, the Raman light is included in the scattered light. Since the light is weak, it is required to significantly improve the light collection efficiency in order to properly obtain the spectral information. Therefore, in the present invention, the scattered light sampling means as shown in FIG. 5 is provided. Scattered light sampling means 1 shown in FIG.
8 is a flat-headed optical fiber 60, and the optical fiber 60
Pointed probe 6 provided in the approximately central portion of the flat head surface 62 of the
4 and gold (A
u) The film 21 is formed. And the flat head surface 6
The reference numeral 2 constitutes a light condensing portion which is provided over the entire circumference of the base portion of the probe 64 and condenses scattered light.

When the probe 64 enters the evanescent light field 16, scattered light is generated from the tip of the probe 64, and most of the scattered light L is the optical fiber 6.
The light traveling toward the flat head surface 62 of 0 and entering the fiber 60 from the flat head surface 62 is directly sent to the notch filter 32. The scattered light generated by the probe 64 entering the evanescent light field 16 as described above is highly efficiently captured by the flat head surface 62. FIG. 6 shows a manufacturing process of the scattered light sampling means 18 of the microscope 30 according to the present invention.

In the method shown in the figure, one end of the optical fiber is subjected to chemical etching using an HF-NH ₄ F system buffer solution. First, as shown in FIG. 1A, in the silica-based fiber 200, the cladding 202 has a pure SiO ₂
Single mode fiber (initial diameter 125 μm) made of glass and core 204 made of SiO ₂ glass containing GeO _2.
Is used. As a pre-stage of etching for sharpening, an etching process for reducing the cladding diameter is performed. That is, when one end of the fiber 200 is cut and immersed in a buffer solution, the etching rate changes from the peripheral portion to the central portion of the core 204 depending on the doping amount. For example, the end face of a high-concentration-doped fiber having a GeO ₂ addition rate of 25 mol% is converted into a volume ratio HF (50%): NH ₄ F (40
%): H ₂ O = X: 1: 1 when etched with a buffer solution mixed with X <1.7 at room temperature (about 23 ° C.).
Then, the core is dented, but when X> 1.7, it sharpens.

Therefore, in the first step, the cladding diameter is reduced (30 μm or less) by using a buffer solution of X = 1.7 (the etching rate of the cladding and the core are the same). The clad diameter can be controlled by controlling the etching time and the like. Next, as the second stage, X>
Sharpen with the buffer solution of 1.7. For example, when X = 5, the acute angle becomes 25 °, and the tip radius of curvature becomes 5 nm or less, which is the minimum in 1 hour. The radius of curvature of the tip increases to about 10 nm after this optimum time, but it does not exceed this value. When X = 10, the acute angle becomes the minimum of 20 °.

The end portion of the optical fiber formed as described above has a flat-headed optical fiber 60 as shown in FIG.
And a pointed probe 64 provided substantially in the center of the flat-faced surface of the optical fiber 60. Then, while rotating the optical fiber, vacuum vapor deposition of gold is performed on the tip of the pointed probe to form the scattered light collecting means shown in FIG.

By using the photon scanning tunneling microscope 30 as described above, (1) identification of submicron particles or less in a super clean room, (2) shape observation and Raman spectroscopic analysis of semiconductor devices integrated in an ultra-high density, (3)
Nanoscale characterization of ceramics and polymer materials in microscopic areas, (4) Nanoscale structural diffraction of DNA or protein in living tissue,
(5) It can be applied to basic research and improvement of near-field optics.

[0024] By establishing the physical property evaluation means in the extremely small area, a completely new fine processing technology and manufacturing process technology are created, and in the field of biochemistry, functional diffraction of various biological tissues such as nerve fibers and brain cells is analyzed. The development of other micro-part analysis devices, such as micro-infrared and micro-differential light, which can be promoted and in which near-field optics is applied to an optical analysis device, can be considered.

[0025]

As described above, according to the photon scanning tunneling microscope of the present invention, since the scattered light collecting means is provided with the scattered light condensing portion over substantially the entire circumference of the probe base, it is highly efficient and evanescent. The scattered light of light can be collected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of a photon scanning tunneling microscope using a general probe.

FIG. 2 is an explanatory diagram showing the relationship between the distance from the sample surface and the evanescent light intensity.

FIG. 3 is an explanatory diagram of a photon scanning tunneling microscope using an apertureless probe.

FIG. 4 is a schematic configuration of a photon scanning tunneling microscope according to an embodiment of the present invention.

FIG. 5 is an explanatory view of scattered light collecting means characteristic of the present invention.

6A and 6B are explanatory views of a manufacturing process of the scattered light collecting unit shown in FIG.

[Explanation of symbols]

 10 sample 16 evanescent light 18 scattered light sampling means 21 metal film 30 photon scanning tunneling microscope 60 flat-headed optical fiber 62 flat-headed surface 64 pointed probe

Claims (4)

[Claims] 1. A photon scanning tunneling microscope equipped with scattered light sampling means for sampling scattered light generated by causing a probe to enter the field of evanescent light on the surface of a sample to be measured, wherein the scattered light sampling means is the probe. A photon scanning tunneling microscope having a condensing unit for condensing scattered light provided over substantially the entire circumference of the base. 2. The microscope according to claim 1, wherein the scattered light collecting means comprises an optical fiber and a pointed probe provided substantially in the center of the end face of the optical fiber, and the pointed probe surface is made of metal. A photon scanning tunneling microscope characterized in that a film is formed. 3. The microscope according to claim 1, wherein the separating means separates the scattered light collected by the scattered light collecting means into Rayleigh light and Raman light, and the Rayleigh light intensity separated by the separating means. A separation information acquisition unit for acquiring separation information between the surface of the sample to be measured and the probe, and a spectrum information acquisition unit for separating Raman light separated by the separation unit to obtain Raman spectrum spectrum information, Photon scanning tunneling microscope. 4. The microscope according to claim 3, further comprising X and Y axis scanning means for scanning the scattered light sampling means on the surface of the sample to be measured in the X and Y axis directions, at each measurement site on the surface of the sample to be measured. Photon scanning tunneling microscope capable of simultaneously acquiring separation information and spectral information at the same time.