JP2004101424A - Scattering-type near-field microscope and scattering-type near-field spectroscopic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of improving an S/N ratio and contrast more than conventional technology in a scattering-type near-field microscope and efficiently condensing a backscattering component in the case of sample measurement on a non-transmitting sample. <P>SOLUTION: A metal or a dielectric for scattering an evanescent field is provided for only the vicinity of a tipmost part of a probe provide for a cantilever. A part or the whole of the cantilever is constituted of an optically transparent material so that part or the whole of light backscattered at the tip of the probe and condensed by a condensing means may be transmitted through the cantilever and condensed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, the evanescent light generated on the sample surface is scattered by a cantilever having a probe structure made of a metal or a dielectric, and the scattered light is detected. The present invention relates to a scattering type near-field microscope and a scattering type near-field spectroscopy system for measuring the following.
[0002]
[Prior art]
A first conventional technique of the conventional scattering type near-field microscope will be described with reference to FIG. 6 (for example, see Patent Document 1).
[0003]
The conventional scattering type near-field microscope uses a needle-like probe 107 made of metal or dielectric and having a sharpened tip, and uses a total reflection optical system including a light source 104, a condenser lens 105, and a prism 103, The probe 107 is inserted into a region where evanescent light having fine structural information generated on the surface of the sample 101 by an optical system or a reflection optical system (a transmission optical system and a reflection optical system are not shown) exists, and a probe tip is inserted. And the evanescent light interact with each other, and the scattered light that can be generated by the interaction is condensed by the condensing lens 109 and detected by the photoelectric detector 110. We are doing fine structure measurement. Generally, evanescent light has low intensity and is very difficult to detect. However, in this method, scattered light is enhanced by the action of a metal or a dielectric at the tip of the probe, and the detection efficiency is improved.
[0004]
Further, as an application example of the first related art, a second related art of a scattering type near-field microscope using a straight metal probe will be described with reference to FIG. 7 (for example, see Patent Document 2).
[0005]
In the second conventional technique, a probe 203 made of a dielectric or metal having a sharpened tip is inserted into evanescent light generated on the surface of a sample 202, and the intensity of scattered light scattered at the tip of the probe is measured. The optical information of the sample is measured at a high resolution exceeding the diffraction limit. The intensity of evanescent light generated on the sample surface decreases exponentially with distance from the sample. For this reason, the evanescent light generated on the sample surface contains shape information and optical information of the sample surface. Therefore, usually, while keeping the distance between the probe and the sample surface constant, the sample and the probe are relatively scanned, and the measurement is performed while separating the shape information and the optical information. In the second conventional technique, the probe 203 is vibrated in parallel with the surface of the sample 202, and the amplitude of the probe 203 at that time is measured by a displacement detector including a semiconductor laser 210, lenses 211, 212, and a two-segment photodetector 213. By doing so, control is performed so that the distance in the height direction between the probe 203 and the sample 202 becomes constant. When the probe is brought close to the sample, a shear force acts on the probe tip 203a. The shear force changes the amplitude and phase of the probe. Since the shear force depends on the distance from the sample surface, the distance between the probe and the sample can be controlled by measuring the amplitude or phase of the probe.
[0006]
Further, a third related art of a scattering near-field microscope which is another application example of the first related art will be described with reference to FIG. 8 (for example, see Non-Patent Document 1).
[0007]
In the third prior art, a probe 301 in which silver is coated on a cantilever with a probe for an atomic force microscope is used. In the third prior art, an oil immersion objective lens 303 having an NA of 1.4 is arranged on the back surface of a transmission sample 302, and the sample is irradiated with a laser beam 304 having a wavelength of 488 nm as an excitation source from the back surface of the sample through the objective lens. I do. At this time, a mask (not shown) is inserted on the optical path so as to cut a laser beam incident on a portion where the NA of the objective lens is 1 or less. At this time, only light having an NA of 1 or more is incident on the sample, and this light is totally reflected at the surface of the sample, and evanescent light is formed on the surface of the sample. When the cantilever probe 301a is inserted into the evanescent light, the evanescent light is scattered. At this time, the scattered light is enhanced by the action of silver coated on the probe. The scattered light 305 is condensed by the same objective lens 303 as the condensed excitation light, and the excitation light is removed by a notch filter (not shown). (Not shown), Raman spectroscopy is performed with a resolution exceeding the diffraction limit. In the third prior art, the distance between the probe and the sample is controlled by the atomic force acting between the probe tip 301a and the sample 302. As in the second prior art, the shape information and the optical information contained in the evanescent light are controlled. Can be measured separately.
[0008]
[Patent Document 1]
Japanese Patent No. 3196945 (Section 2-4, FIG. 1)
[0009]
[Patent Document 2]
JP-A-9-281122 (Section 3-7, FIG. 4)
[0010]
[Non-patent document 1]
Norihiko Hayazawa, Yasushi Inouye, Zouheir Sekkat, Satoshi Kawabata, Near-field Raman scattering enhanced through the most common technical bulletin 2003
[0011]
[Problems to be solved by the invention]
However, in the prior arts shown in the first to third aspects, the metal or dielectric for scattering the evanescent light exists not only near the tip of the probe but also in a portion distant from the tip of the probe. Even the far-field component other than the evanescent component is scattered, and this is mixed into the signal to lower the S / N ratio and the resolution.
[0012]
Furthermore, in the first to third conventional techniques, when measuring a non-transmissive sample or the like, it is necessary to generate evanescent light by a reflection optical system and collect the backscattered component. At this time, the probe itself blocks the light incident by the reflection optical system and the backscattered light. Furthermore, the components arranged above the sample, such as the probe, the probe holder, and the bending amount detecting means, impose restrictions on the arrangement of the reflecting optical system and the condensing optical system for incidence. For this reason, the reflection optical system and the condensing optical system cannot be arranged at positions where they can be measured efficiently, and the S / N ratio and the resolution are reduced.
[0013]
An object of the present invention is to provide a scattering near-field microscope and a scattering near-field spectroscopy system that can solve the above-mentioned problems.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, in the scattering type near-field microscope of the present invention, a cantilever having a probe, a cantilever holder for holding the cantilever, a sample holder arranged at a position facing the probe, and a cantilever A deflection amount detection mechanism for detecting the deflection amount of the probe, a fine movement mechanism for adjusting the distance between the probe and the sample, a scanner for relatively moving the probe and the sample in a two-dimensional plane, and a deflection amount A servo circuit for adjusting the distance between the microprobe and the sample by operating the fine movement mechanism based on a signal from the detection mechanism, evanescent light generating means for generating evanescent light on the sample surface, and a sample surface Light collecting means for collecting the scattered light generated when the probe is brought close to the evanescent light generated in the light source, and an optical detector for measuring the intensity of the scattered light. In scattering near-field microscope having a section, provided only the metal or dielectric portion in the vicinity of the leading edge portion of the probe.
[0015]
Further, in the present invention, part or all of the cantilever is made of an optically transparent material, and a metal or dielectric portion is provided only near the tip of the probe, so that the backscattered light at the tip of the probe is provided. Part or all of the structure is configured to transmit light through the cantilever, so that scattering other than at the tip of the probe is suppressed as much as possible, and the backscattered component transmitted through the cantilever can be collected.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiment described here is merely an embodiment of the present invention, and the present invention is not limited to the embodiment.
[0017]
(1) First embodiment example
FIG. 1 shows a first embodiment of a scattering type near-field microscope according to the present invention. In the present embodiment, an objective lens 2 having a numerical aperture of 1 or more (here, an oil immersion lens having a numerical aperture of 1.4) is disposed below the transparent sample holder 1. Light from the laser 3 is introduced into the objective lens 2. The laser light is converted into parallel light by the beam expander 4, bent by 90 ° by the dichroic mirror 5, and guided to the objective lens. At this time, a disk-shaped light-shielding plate 6 is inserted into the optical path between the beam expander 4 and the dichroic mirror 5 so as to cut off the light having a numerical aperture of 1 or less from the light incident on the objective lens 2. With such an optical system, light of a portion having a numerical aperture of 1 or more is incident on the sample 7 from the objective lens 2 so that the light is incident at a total reflection angle, and evanescent light is formed on the surface of the sample 7.
[0018]
The sample 7 is mounted on the sample holder 1, and the sample holder 1 is provided with a three-axis fine movement mechanism 8 which is composed of a piezoelectric element and can scan in a two-dimensional plane and perform a servo operation in a height direction. ing.
[0019]
On the other hand, above the sample 7, a cantilever holder 10 is arranged, and a cantilever 11 made of a silicon substrate and provided with a sharpened probe 11a at the tip is attached. Metal is deposited only on the tip of the probe 11a. In this embodiment, silver is used as the metal to be deposited. The silver deposition range is limited to a height of approximately 200 nm or less, preferably 100 nm or less, from the tip of the probe. Here, in the present embodiment, as a method of depositing metal only on the tip, a metal thin film is deposited on the entire probe, and the remaining metal is removed from only the approximately 100 nm portion at the foremost portion by a focused ion beam (FIB). And manufactured by removing.
[0020]
The bending of the cantilever 11 is detected by an optical lever optical system 12 disposed above the cantilever. The optical lever optical system is configured such that light from a laser diode 13 is condensed on the back surface of the cantilever 11 by a lens 14 and light reflected from the cantilever 11 is detected by a photodetector 15 having a light-receiving surface divided into four parts. The wavelength of the laser diode 13 is different from the wavelength to be measured. When the cantilever 11 bends, the spot on the photodetector 15 moves up and down. The deflection of the cantilever 11 is measured by detecting the difference in light intensity between the divided surfaces at this time.
[0021]
The cantilever holder 10 is mounted on a coarse movement stage 18 for bringing the probe 11a close to the surface of the sample 7. The coarse movement stage 18 uses the mechanism of the stepping motor 19 and the feed screw 20 to support the coarse movement stage 18 on which the cantilever holder 10 and the optical lever optical system 12 are mounted with the leg of the micrometer head 21 as a fulcrum. It is a configuration that makes them approach each other.
[0022]
When the probe 11a and the sample 7 are brought close to the region where the atomic force acts with the device configured as described above, the cantilever 11 bends due to the atomic force acting on the tip of the cantilever 11. Since the amount of bending depends on the distance between the probe 11a and the sample 7, the fine movement mechanism 8 is servo-operated by a servo mechanism (not shown) so that the amount of bending is constant, thereby causing the sample 7 and the probe 11a to move. The distance can be kept constant.
[0023]
Evanescent light generated on the surface of the sample 7 generally exists between 100 nm and 200 nm, and attenuates along an exponential curve as the distance from the surface of the sample 7 increases. By positioning the probe 11a and the sample 7 in this area while performing servo operation, evanescent light is scattered at the probe tip 11a, and the light scattered at the probe tip 11a is enhanced by the electric field enhancing action of silver. And converted into propagating light.
[0024]
This scattered light is collected by the same lens 2 as the lens used to enter the excitation light. When condensing light, the light is condensed on the entire objective lens including the portion having a numerical aperture of 1 or less. A desired detection signal is selected from the condensed optical signals by the dichroic mirror 5 and the absorption filter 22, is bent by 90 degrees by the total reflection mirror 23, is imaged by the imaging lens 24, and then is subjected to the short-pass filter. The component of the laser diode light of the optical lever optical system is cut by 25 and guided to the photodetector 26. Here, a photomultiplier tube was used as the photodetector 26, and a photon counter 27 was used to measure the light intensity by a photon counting method.
[0025]
In the scattering near-field microscope configured as described above, the sample is scanned in a two-dimensional plane while the height of the sample 7 and the probe 11a is kept constant by the three-axis fine movement mechanism 8, so that the sample is scanned on the sample surface. The mapping of the optical information is measured at a resolution above the diffraction limit. Further, by mapping the servo signal used for the control in the height direction, an uneven image of the sample surface can be measured at the same time.
[0026]
In a conventional scattering-type near-field microscope, metal or a dielectric material is uniformly applied to the tip of the probe other than the tip of the tip. The stray light component is also scattered by the probe, which causes noise to cause a reduction in the S / N ratio and the resolution. However, in the present invention, since the metal for scattering is limited to only the tip portion, These noise components are reduced, and the S / N ratio and the resolution are improved as compared with the conventional scattering type near-field microscope. Here, the height of the metal to be deposited is set to approximately 100 nm or less, but the S / N ratio and the resolution are further improved by further reducing the height and locally depositing the metal.
[0027]
(2) Second embodiment example
FIG. 2 shows a second embodiment of the scattering near-field microscope according to the present invention. In the present embodiment, the sample stage 31 is arranged on the base 30, and the sample 32 is placed on the sample stage 31. Above the sample 32, there is disposed a three-axis fine movement mechanism 33 which is constituted by a piezoelectric element and is capable of scanning in a two-dimensional plane and performing a servo operation in the height direction. The three-axis fine movement mechanism 33 has a cantilever holder 34 and a cantilever 36. An optical head 35 accommodating a small optical lever optical system for measuring deflection is mounted so as to operate integrally with the three-axis fine movement mechanism 33.
[0028]
The cantilever holder 34 is attached with a cantilever 36 made of silicon oxide and provided with a sharpened probe 36a at the tip. Metal is deposited only on the tip of the probe. In this embodiment, silver is used as the metal to be deposited. The deposition range of silver is limited to a height within approximately 100 nm from the tip of the probe. Also in this embodiment, as a method of attaching metal only to the tip portion, a metal thin film is deposited on the entire probe, and the remaining metal is removed by FIB except for about 100 nm at the foremost portion, and manufactured by FIB. did.
[0029]
Further, a piezoelectric element 37 for exciting the cantilever 36 is attached to the cantilever holder 34, the cantilever 36 is excited, and the amplitude is detected by the optical head 35.
[0030]
Above the surface of the sample 32, a laser light source 38 is arranged. Laser light is incident from a direction satisfying the total reflection angle and the optical path does not interfere with the cantilever 36, and generates evanescent light on the surface of the sample 32.
[0031]
The three-axis fine movement mechanism 33 is mounted on a coarse movement mechanism 39 for bringing the sample 32 and the cantilever 36 close to each other. As the coarse movement mechanism, a mechanism using a stepping motor 40 and a feed screw (not shown) was used.
[0032]
An objective lens 41 for collecting scattered light is arranged at a position above the sample where backscattered light can be detected. The light collected by the objective lens 41 is reflected by the total reflection mirror 42, the excitation light component is cut by the notch filter 43, and the light of the semiconductor laser for light leverage is cut by the short-pass filter 44, and then the image is formed. An image is formed by the lens 45 and guided to the photodetector 46. In this embodiment, a photomultiplier tube is used as a photodetector.
[0033]
As shown in FIG. 3, a semiconductor laser 49 is disposed obliquely above the back of the cantilever 36 inside the optical head 35, and the laser beam is condensed by a condenser lens 50 on the back of the cantilever 36, and reflected from the cantilever 36. The light is detected by a four-division photodiode 51, and an opening window 52 is provided at the center of the optical head 35 so that backscattered light can be collected by an objective lens 41 disposed above the cantilever 36. Is provided.
[0034]
In this embodiment, the cantilever 36 is vibrated in the vicinity of the resonance frequency of the cantilever to change the amplitude of the cantilever 36 due to the atomic force or intermittent contact when the probe 36a approaches the sample 32. And the distance between the sample 32 and the sample 32 is controlled. Since the amount of change in the amplitude at this time depends on the distance between the probe 36a and the sample 32, a servo operation is performed by a servo mechanism (not shown) so that the amplitude is constant. It is possible to keep the distance between them constant. In addition, it is also possible to perform control using a phase and a frequency instead of the amplitude.
[0035]
In this embodiment, the incident laser light is modulated by a pulse signal synchronized with the vibration frequency of the cantilever 36, and the signal detected by the photomultiplier tube 46 is synchronized with the vibration frequency of the cantilever 36. The S / N ratio was improved by using an optical measurement system in which only the scattered light component detected by the lock-in amplifier 47 was lock-in detected. Here, the amplitude of the cantilever 36 is usually several nm to several tens nm. Since the evanescent light generated on the sample surface attenuates along an exponential function curve with respect to the distance from the sample surface, strictly speaking, the intensity of the evanescent light changes with the vibration in the direction perpendicular to the sample surface. By applying ON / OFF modulation to the incident light by a pulse signal and detecting lock-in of the scattered light as in this method, it is possible to minimize the fluctuation of the evanescent light intensity due to the vibration of the cantilever. . Further, since the resolution decreases as the probe 36a moves away from the surface of the sample 32, the resolution is improved by providing incident light only in a portion where the probe 36a is close.
[0036]
When performing lock-in detection, any modulation is applied to the incident light regardless of the oscillation frequency of the cantilever, and the scattered light component synchronized with this frequency is lock-in detected, or the incident light is a continuous light. As a method, lock-in detection of only a component synchronized with the vibration frequency of the cantilever can be considered, and in each case, the S / N ratio can be improved.
[0037]
The conventional scattering-type near-field microscope has a configuration in which a silicon cantilever optically opaque to visible light is used, and a metal for scattering is further deposited on the entire surface of the cantilever. For this reason, most of the backscattered light is blocked by the cantilever, and it is necessary to arrange the objective lens for condensing obliquely above the sample surface so as not to be blocked by the cantilever. In this case, only part of the backscattered light could be collected by the objective lens, and the light collection efficiency was extremely poor.
[0038]
In the present embodiment, the cantilever 36 and the probe portion 36a are made of silicon oxide which is optically transparent to visible light, and the metal adheres only to a very small part of the tip. The portion where light is blocked is significantly reduced, and the light-collecting objective lens 41 can be disposed behind the cantilever 36, so that light-collecting efficiency is greatly improved. Furthermore, since the metal attachment portion is limited to the region of the sample surface where the evanescent light exists, the scattering of the far-field component is prevented, and the influence of the noise component due to the far-field light scattering is reduced.
[0039]
With the scattering near-field microscope configured as described above, optical information exceeding the diffraction limit can be obtained without being affected by the shape. Further, the shape information of the sample surface can be obtained simultaneously from the feedback signal of the distance control.
[0040]
In the present embodiment, the evanescent light generating means is arranged above the sample to excite light from the outside, but the evanescent light generating means is not limited to this method. It is also applicable to a sample in which evanescent light is present on the sample surface without using an excitation light source as in the case of the intensity distribution measurement described above and the intensity distribution measurement at the boundary surface of the optical waveguide.
[0041]
Further, the arrangement of the focusing objective lens is not limited to the position directly above the cantilever, and the present invention includes a case where the focusing is performed from an oblique direction or the like.
[0042]
(3) Third embodiment example
FIG. 4 shows a scattering type near-field spectroscopy system according to a third embodiment of the present invention.
In this embodiment, an optical system similar to that of the scattering type near-field microscope of the first embodiment is used for a transparent sample. That is, an objective lens 54 having a numerical aperture of 1 or more (here, an oil immersion lens having a numerical aperture of 1.4) is disposed below the transparent sample holder 53. Light from a laser 55 is introduced into the objective lens 54. The laser light is converted into parallel light by the beam expander 56, bent by 90 ° by the half mirror 57, and guided to the objective lens 54. At this time, a disk-shaped light-shielding plate 58 is inserted into the optical path between the beam expander 56 and the half mirror 57 so as to cut off the light having a numerical aperture of 1 or less from the light incident on the objective lens 54. With such an optical system, light of a portion having a numerical aperture of 1 or more is incident on the sample 59 from the objective lens 54, so that the light is incident at a total reflection angle, and evanescent light is formed on the surface of the sample 59. The sample 59 is placed on a sample holder 53, and the sample holder 53 includes a three-axis fine movement mechanism 60 which is constituted by a piezoelectric element and is capable of scanning in a two-dimensional plane and performing a servo operation in a height direction. Installed.
[0043]
In the present embodiment, a laser 61 is also arranged obliquely above the sample 59 for a non-transmissive sample so that a laser for generating evanescent light can be made incident thereon, and the rear side scattered by the probe 62a is scattered. An objective lens 63 for condensing light is also provided on the rear side of the cantilever 62 so that the scattered component can also be condensed. Further, a three-axis fine movement mechanism 64, which is constituted by a piezoelectric element and is capable of scanning in a two-dimensional plane and performing a servo operation in the height direction, is arranged above the sample 59. The three-axis fine movement mechanism 64 has a cantilever holder 65 and a cantilever An optical head 66 containing a small optical lever optical system for measuring deflection is mounted so as to operate integrally with the three-axis fine movement mechanism. The configuration of the optical head 66 is the same as that shown in FIG. 3 of the second embodiment. A semiconductor laser is disposed diagonally above the back of the cantilever 62, and the laser is focused on the back of the cantilever by a condensing lens. Light is collected and the reflected light from the cantilever is detected by a 4-division photodiode. Backscattered light can be collected at the center of the optical head by an objective lens located above the cantilever. This is a structure in which an opening window is provided (the internal structure of the optical head is not shown).
[0044]
The three-axis fine movement mechanism 64 provided above the sample is attached to a coarse movement stage 68 driven by a stepping motor 67, and the coarse movement stage 68 allows the probe 62a to approach the sample 59. .
[0045]
In the present embodiment, the probe 62a and the sample 59 are brought closer to the region where the atomic force acts, and the bending of the cantilever caused by the atomic force acting on the tip 62a of the cantilever is measured, so that the amount of the bending becomes constant. The distance between the sample 59 and the probe 62a is kept constant by servo-operating the fine movement mechanism 60 or 64 using a servo mechanism (not shown). Note that a method in which control is performed while vibrating the cantilever as in the second embodiment can also be used.
[0046]
A tip 62a made of silicon oxide is provided as a cantilever 62, and a sharpened tip 62a is provided at the tip. Silver is vapor-deposited at a height of about 100 nm at the tip of the tip, and further, at the tip of the tip. The one provided with a minute opening having a diameter of about 50 nm was used. This cantilever is manufactured by depositing silver on the entire probe part, leaving only the portion about 100 nm in height from the tip, removing the remaining metal with FIB, and removing the foremost part with FIB. This was processed to produce a small aperture of about 50 nm.
[0047]
In the present embodiment, evanescent light is scattered by the metal around the opening of the probe 62a, and the component of the scattered light that has transmitted through the sample 59 is the same objective lens 54 on the transmission side as the lens used to enter the excitation light. The light is focused. When condensing light, the light is condensed on the entire objective lens 54 including the portion having a numerical aperture of 1 or less. The condensed optical signal passes through the half mirror 57, is bent 90 degrees by the total reflection mirror 69, is further converted in the optical path by the total reflection mirrors 70 and 71, and is short-passed by the short-pass filter 72. After the component of the diode light is cut off, the excitation light component is further cut off by the notch filter 73, the image is formed by the imaging lens 74, and the light is guided to the spectroscopy system 75.
[0048]
The backscattering component is collected at the opening of the probe tip 62a, passes through the inside of the probe transparent to visible light, and is collected by the objective lens 63 for light collection. In addition, components of the backscattered light that are not collected at the aperture can be collected by the objective lens 63 through the cantilever 62. After the light paths of these lights are converted by the two total reflection mirrors 76 and 77, they are guided to the spectroscopy system 75 through the same light path as the light path of the transmitted light. Here, the total reflection mirror 70 is configured to be switchable, and is switched to through when measuring the backscattering component.
[0049]
The scattering-type near-field spectroscopy system configured as described above is used for transmitting samples, non-transmitting samples, or samples in which evanescent light exists on the sample surface by a method other than the evanescent light generating means of the apparatus. It is possible to select and use an incident method and a light collecting method. Further, by switching the total reflection mirror 70 to a half mirror, both the transmitted light and the backscattered component can be measured simultaneously.
[0050]
The two three-axis fine movement mechanisms 60 and 64 normally use the three-axis fine movement mechanism 60 provided below the sample when condensing transmitted light, and the three-axis fine movement mechanism provided above the sample when collecting backscattered components. Although 64 is used, these can be arbitrarily selected and used depending on the measurement target.
[0051]
In the present embodiment, the spectral intensity can be measured using a spectral system 75 including a spectroscope and a cooled CCD camera. By using this system, it is possible to measure the Raman spectrum and the fluorescence spectrum at an arbitrary position of the sample with a high resolution exceeding the diffraction limit. In addition, by measuring the spectrum intensity while relatively scanning the sample and the probe, spectrum mapping in a two-dimensional plane is possible. In particular, in the present embodiment, since the cantilever coated with silver is used, the intensity of the scattered light can be improved by the electric field enhancing effect, and the weak light measurement such as Raman spectroscopy can be realized.
[0052]
(4) Other embodiments
▲ 1 ▼ Cantilever
In the present invention, any material can be used as the material of the cantilever when the backscattering component is transmitted through the cantilever and then collected by the objective lens as long as it is optically transparent to the detection light. For example, in the second embodiment and the third embodiment, the cantilever made of silicon oxide is used. However, silicon oxide is optically transparent mainly in the visible to near infrared region and can be used in this range. Also, a silicon nitride cantilever is optically transparent to light up to near infrared and can be used in this range. In addition, silicon can transmit light of about 1.2 μm or more, and a silicon cantilever can be used in this range.
[0053]
Further, the cantilever and the probe may be made of different materials. For example, FIG. 5 shows an example of a cantilever used for detecting visible light. In the cantilever 80, the probe portion 80a uses silicon oxide that is optically transparent to visible light, and the cantilever portion 81b uses an optically opaque silicon material. By using such a cantilever, the laser for displacement detection is efficiently reflected by the cantilever with respect to the laser for displacement detection such as an optical lever, and light leaking to the sample side is cut by the cantilever. There are benefits.
[0054]
The metal provided at the tip of the probe is not limited to silver. For example, in addition to metals such as gold, platinum, tungsten, and aluminum, dielectrics and the like can be used according to the purpose.
[0055]
Desirably, these metals and dielectrics have an effect of enhancing scattered light, and the S / N ratio is improved by increasing the enhancement rate of the scatterer provided at the tip compared to the base material of the probe.
[0056]
The method of providing a metal or a dielectric is not limited to the vapor deposition described in the embodiment, but may be, for example, a method of depositing the tip of the probe using FIB.
[0057]
The region where these metal or dielectric scatterers are provided may be only the region where the evanescent light exists, and is usually provided at a height within 200 nm from the tip of the probe. This height can be arbitrarily selected within 200 nm depending on the purpose. For example, in order to obtain high resolution, it is better to provide a scatterer only in a region as narrow as possible.
[0058]
In the case where a small opening is formed at the tip of the probe, the probe portion may be physically formed from the back of the cantilever to the tip of the probe by FIB or the like in addition to a solid structure as described in the third embodiment. A method of forming a hollow opening is also conceivable.
[0059]
Further, the shape of the tip of the probe is arbitrary, and for example, it may be processed into a triangular shape, a rhombus, or the like in order to improve the intensity of scattered light.
[0060]
(2) Control method
In the first to third embodiments, the distance between the probe and the sample is controlled while detecting the static deflection of the cantilever, or the cantilever is vibrated up and down with respect to the sample to detect the deflection. Although the method of controlling the distance between the needle and the sample was used, the distance control method between the probe and the sample in the present invention is not limited to these methods. For example, the scattering intensity of evanescent light, the sample and the probe A method of controlling the distance by a tunnel current flowing therebetween is also conceivable, and these are all included in the present invention.
[0061]
【The invention's effect】
As described above, the present invention uses a cantilever in which a metal or a dielectric for scattering an evanescent field is provided only in the vicinity of the tip of the probe in a region of approximately 200 nm or less, and a sample is generated by an evanescent light generating means. The evanescent light generated on the surface is scattered, and the scattered light transmitted or backscattered through the sample is condensed by the condensing means, so that the light intensity can be detected and the spectrum can be measured.
[0062]
In the scattering-type near-field microscope configured in this manner, the scattered light and stray light scattered at the tip of the probe are not scattered except at the tip of the cantilever, and the metal-attached portion has the presence of evanescent light on the sample surface. Therefore, the scattering of the far-field component is prevented, and the influence of the noise component caused by the far-field light scattering is reduced. As a result, the S / N ratio and contrast are improved as compared with the conventional scattering type near-field microscope.
[0063]
Also, part or all of the cantilever is made of an optically transparent material so that part or all of the light that is backscattered at the tip of the probe and condensed by the light condensing means passes through the cantilever and is condensed. The scattering type near-field microscope was constructed by providing a metal or dielectric in a region of about 200 nm or less near the tip of the probe.
[0064]
In the scattering near-field microscope configured as described above, the portion where the backscattered light is blocked by the cantilever is significantly reduced, and the condensing objective lens can be arranged behind the cantilever. It is greatly improved, and the S / N ratio and the contrast are improved.
[0065]
Further, a minute aperture is provided at the tip of the probe, the evanescent light is scattered by the metal around the aperture, and the backscattered component is collected, thereby further improving the light collection efficiency.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment of a scattering type near-field microscope of the present invention.
FIG. 2 is a configuration diagram of a second embodiment of the scattering type near-field microscope of the present invention.
FIG. 3 is a configuration diagram of an optical head according to a second embodiment.
FIG. 4 is a configuration diagram of a third embodiment of the scattering near-field spectroscopy system of the present invention.
FIG. 5 is a configuration diagram of a cantilever according to another embodiment of the present invention.
FIG. 6 is a configuration diagram of a first related art.
FIG. 7 is a configuration diagram of a second conventional technique.
FIG. 8 is a configuration diagram of a third conventional technique.
[Explanation of symbols]
2,41,54,63 Objective lens
3,38,55,61 laser
6,58, Light shield
7 samples
8,33,60,64 3-axis fine movement mechanism
9,78 base
10,34,65 Cantilever holder
11,36,62,80 Cantilever
12. Optical lever optical system
16,17 mirror
18,68 Coarse movement stage
26,46 Photodetector
27 Photon Counter
35,66 Optical head
39 Coarse movement mechanism
47 Lock-in Amplifier
48,79 props
75 Spectroscopy system

Claims (17)

A cantilever having a probe structure, a cantilever holder for holding the cantilever, a sample holder arranged at a position facing the probe and holding a sample, and a bend for detecting the amount of deflection of the cantilever. An amount detecting mechanism, a fine movement mechanism for adjusting a distance between the probe and the sample, a scanner for relatively moving the probe and the sample in a two-dimensional plane, and a signal based on a signal from the bending amount detecting mechanism. A servo circuit for operating the fine movement mechanism to adjust the distance between the microprobe and the sample, evanescent light generating means for generating evanescent light on the sample surface, and a probe for evanescent light generated on the sample surface A light condensing means for condensing scattered light generated when the object is brought into proximity, and a light detection unit for measuring the intensity of the scattered light. Scattering the near-field microscope, characterized in that a metal or dielectric for scattering cent light near the most distal portion of the probe. 2. The scattering proximity device according to claim 1, wherein a metal or a dielectric material provided near the tip of the probe is provided on a part or the whole of a region within a height of 200 nm from the tip of the probe. 3. Field microscope. The scattering near-field microscope according to claim 1, wherein the light condensing means is arranged so as to be able to condense light scattered at the tip of the probe and transmitted through the sample. 3. The scattering near-field microscope according to claim 1, wherein the light condensing means is arranged so as to be able to condense the light scattered backward at the tip of the probe. 3. The light-collecting means according to claim 1, wherein the light-collecting means is arranged so that light scattered at the tip of the probe and transmitted through the sample and light scattered backward can be simultaneously collected. Scattering near-field microscope. A part of or the whole of the cantilever is made of an optically transparent material so that part or all of the light backscattered at the tip of the probe can be transmitted. Item 6. A scattering near-field microscope according to any one of Items 5. 7. The scattering near-field microscope according to claim 6, wherein an opening is provided at the tip of the probe. 8. The scattering near-field microscope according to claim 6, wherein the optically transparent material forming the cantilever is any one of silicon, silicon oxide, and silicon nitride. 9. The scattering near-field microscope according to claim 1, wherein an opening is provided at the tip of the probe, and the inside of the probe has a hollow structure. 10. The scattering near-field microscope according to claim 6, wherein the optically transparent portion of the cantilever and the cantilever are made of different materials. When the probe approaches or comes into contact with the sample, the cantilever is statically flexed by an external force acting on the tip of the probe, the amount of flexure is detected by a flexure amount detection mechanism, and the sample is compared with the sample based on the flexure amount. The scattering near-field microscope according to any one of claims 1 to 10, wherein a distance between the probes is controlled. When the probe is vibrated in the vertical plane with respect to the sample and the sample and the probe come into close or intermittent contact, the amplitude, phase, or frequency obtained from the signal of the deflection detection mechanism The scattering near-field microscope according to any one of claims 1 to 10, wherein a distance between the sample and the probe is controlled based on the information. The evanescent light generated on the sample surface is subjected to modulation at an arbitrary frequency, and only the frequency component synchronized with the modulation signal is detected out of the scattered light scattered at the tip of the probe. 13. The scattering near-field microscope according to any one of 12. 13. The scattering near-field microscope according to claim 12, wherein the detection unit detects only a scattered light component synchronized with an excitation frequency of the probe. The evanescent light generated on the sample surface is subjected to modulation synchronized with the frequency of the probe, and among the scattered light scattered at the tip of the probe, only the frequency component synchronized with the modulation signal is detected. The scattering near-field microscope according to claim 12, wherein: The scattering near-field microscope according to any one of claims 1 to 12, wherein the detected signal is detected by a photon counting method. 17. The scattering near-field spectroscopy system according to claim 1, wherein a spectrum of the scattered light is measured by a spectrum system including a spectroscope and a photodetector.

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