JP4388559B2 - Scanning near-field microscope - Google Patents

Description

  The present invention relates to a scanning near-field microscope that is one of scanning probe microscopes and measures optical characteristics in a fine region of a measurement substance.

  A scanning probe microscope represented by an atomic force microscope (AFM) and a scanning tunneling microscope (STM) is widely used because it can observe a fine shape of a sample surface.

  On the other hand, there have been attempts to measure the optical properties and shape of a sample by bringing a probe made of an optical medium with a sharp tip close to the sample to be measured below the wavelength of light, and several near-field optical microscopes have been proposed. ing. As one of these devices, the tip of the optical fiber probe held perpendicular to the sample is vibrated horizontally with respect to the sample surface, and the change in the amplitude of vibration caused by the friction between the sample surface and the probe tip is irradiated from the tip of the optical fiber probe. By detecting the optical axis misalignment of the laser beam that has passed through the sample and moving the sample with the fine movement mechanism, the distance between the probe tip and the sample surface is kept constant, and the surface shape is detected from the signal intensity input to the fine movement mechanism. An apparatus for measuring the light transmittance of a sample has been proposed.

  In Patent Document 1, an optical fiber probe shaped like a bowl is used as an AFM cantilever, and at the same time as AFM operation is performed, the sample is irradiated with laser light from the tip of the optical fiber probe to detect the surface shape and the optical of the sample. A scanning near-field atomic force microscope for measuring properties is described.

  In scanning probe microscopes that use these light propagator probes, detection of changes in vibration amplitude caused by friction between the sample surface and the probe tip, or detection of atomic force acting on the sample surface and probe tip, is an elastic function of the probe. That is, it is performed by detecting the deflection of the probe. Conventionally, the elasticity of the optical fiber itself has been used as the elastic function.

However, in general, the spring constant of an AFM cantilever is about 1/100 N / m to several N / m, whereas the spring constant of a probe when using the elastic function of the optical fiber itself is several N / m to several 100 N. / M. When the spring constant of the probe is large, not only is there a risk of damage to the sample or the probe tip, but also the detection sensitivity of various physical quantities including atomic force acting between the probe tip and the sample deteriorates. Patent Document 2 describes that a scanning near-field microscope using an optical fiber probe with a small spring constant can be scanned by a contact mode scanning, a scanning friction force microscope, or the like. However, the conventional scanning near-field microscope apparatus cannot measure the potential of the sample surface.
Japanese Patent No. 2704601 JP-A-10-104244

  An object of the present invention is to provide a scanning near-field microscope capable of observing a potential distribution on a sample surface with high resolution in addition to a shape image and a two-dimensional optical characteristic image on the sample surface.

  In order to achieve the above object, a scanning near-field microscope according to the first idea is composed of a light propagating body having a transmission port that transmits light at an end portion, and a conductive metal at a tip portion excluding the transmission port portion. A light propagating probe having a film coating, and the distance between the tip of the light propagating probe and the surface of the sample or medium to be measured between the tip of the light propagating probe and the surface. The surface of the sample is scanned by a two-dimensional scanning unit in a state where the force or other interaction-related force is applied, and the light propagating body is moved along the shape of the surface by a control unit. In a scanning near-field microscope that controls a probe, performs light irradiation or light detection on a minute region of the surface, and simultaneously measures a sample shape and two-dimensional optical information, the tip of the light propagator probe and the Vibration means for vibrating the surface in a relatively vertical direction, displacement detection means for detecting the displacement of the light propagation probe, and a tip of the light propagation probe based on a detection signal output by the displacement detection means; Control means for keeping the surface spacing constant, voltage application means for applying an AC voltage between the tip of the light propagation probe and the sample or medium to be measured, and the light propagation caused by the applied voltage Voltage feedback means for feeding back a voltage so as to eliminate vibration of the body probe.

  According to this invention, the control signal for keeping the distance between the tip of the light propagator probe and the sample surface constant reflects the shape of the sample surface, and the control signal of the light propagator probe caused by the applied voltage is reflected. The signal of the voltage feedback means that feeds back the voltage so as to eliminate vibration reflects the surface potential of the sample surface. Therefore, the optical characteristics of the sample surface, the sample surface shape, and the sample surface potential can be simultaneously measured by inputting and outputting light through the minute opening at the tip of the light propagator probe.

  Further, the scanning near-field microscope according to the second idea includes a light propagating body having a transmission port that transmits light at an end portion, and has a conductive metal film coating at a tip portion excluding the transmission port portion. A probe, and the distance between the tip of the light propagator probe and the sample or medium surface to be measured is determined by an atomic force or other interaction between the tip of the light propagator probe and the surface. The surface of the sample is scanned by a two-dimensional scanning unit in a state of being close to the operating distance in which the force concerned acts, and the light propagating body probe is controlled by the control unit along the shape of the surface. In a scanning near-field microscope that performs light irradiation or light detection on a minute region of the sample and simultaneously measures a sample shape and two-dimensional optical information, a displacement detection means that detects the displacement of the light propagator probe; Control means for keeping the distance between the tip of the light propagating probe and the surface constant based on a detection signal output from the displacement detecting means, and the distance between the tip of the light propagating probe and the sample or medium surface to be measured And a voltage feedback means for feeding back the voltage so as to remove the vibration of the light propagating probe caused by the applied voltage.

  According to this invention, although the distance control method between the probe tip and the sample surface is different from the invention related to the first idea, the control signal for keeping the distance between the tip of the light propagator probe and the sample surface constant is The signal of the voltage feedback means that reflects the shape of the surface and feeds back the voltage so as to remove the vibration of the light propagating probe due to the applied voltage reflects the surface potential of the sample surface. Therefore, the optical characteristics of the sample surface, the sample surface shape, and the sample surface potential can be simultaneously measured by inputting and outputting light through the minute opening at the tip of the light propagator probe.

  Further, the scanning near-field microscope according to the third idea is composed of a light propagating body having a transmission port that transmits light at an end portion, and has a conductive metal film coating at a tip portion excluding the transmission port portion. A probe, and the distance between the tip of the light propagator probe and the sample or medium surface to be measured is determined by an atomic force or other interaction between the tip of the light propagator probe and the surface. The surface of the sample is scanned by a two-dimensional scanning unit in a state of being close to the operating distance in which the force concerned acts, and the light propagating body probe is controlled by the control unit along the shape of the surface. In a scanning near-field microscope that performs light irradiation or light detection on a minute region of the sample and simultaneously measures a sample shape and two-dimensional optical information, the tip of the light propagator probe and the surface are relatively perpendicular to each other. A vibrating means for vibrating, a displacement detecting means for detecting the displacement of the light propagating body probe, and a distance between the tip of the light propagating body probe and the surface is kept constant based on a detection signal output from the displacement detecting means. Control means, voltage applying means for applying an alternating voltage between the tip of the light propagating probe and the surface of the sample or medium to be measured, and vibration of the light propagating probe caused by the applied voltage is removed. A voltage feedback means for feeding back a voltage to the light source, a modulation means for performing light modulation on a light source for performing light irradiation or light detection on a minute region of the surface, and the light propagating probe caused by the applied voltage. Phase detection means for detecting the phase of the vibration detection signal in correspondence with the modulation signal of the modulation means is provided.

  According to the present invention, the control signal for keeping the distance between the tip of the light propagator probe and the sample surface constant reflects the shape of the sample surface, and the control signal of the light propagator probe caused by the applied voltage is recorded. The signal of the voltage feedback means that feeds back the voltage so as to eliminate vibration reflects the surface potential of the sample surface. Therefore, the optical characteristics of the sample surface, the sample surface shape, and the sample surface potential can be simultaneously measured by inputting and outputting light through the minute opening at the tip of the light propagator probe. Further, by performing light modulation on a light source for light irradiation or light detection, it is possible to simultaneously measure a potential image on the sample surface by light irradiation and non-irradiation.

  Further, the scanning near-field microscope according to the fourth idea is the invention according to the first idea to the third idea, wherein the light propagating probe is a substrate-like base and a laminate of at least one layer on the substrate-like base. An optical waveguide layer having a structure is provided, and the optical waveguide layer protrudes from the base to form a beam-shaped cantilever.

  According to the present invention, the light propagating probe can be configured as a cantilever composed of an optical waveguide layer, and a spring constant equivalent to that of a conventional AFM cantilever can be provided. Therefore, it is possible to configure a scanning near-field microscope having sufficient sensitivity for surface potential measurement.

  Further, in the scanning near-field microscope according to the fifth idea, in the inventions of the first idea to the third idea, the light propagating body probe includes a part having an elastic function and a base part supporting the part having the elastic function. The part having the elastic function is formed integrally with a columnar base part supporting the elastic function part and has at least a columnar part, and the outer shape of the columnar part is formed narrower than the outer shape of the columnar base part. It is characterized by that.

  According to the present invention, the light propagating probe can be constituted by a thinned light propagating body, and a spring constant equivalent to that of a conventional AFM cantilever can be provided. Therefore, it is possible to configure a scanning near-field microscope having sufficient sensitivity for surface potential measurement.

  The scanning near-field microscope according to the sixth idea is characterized in that, in the invention of the fourth idea, the light propagating body is a thin film optical waveguide.

  According to the present invention, since an optical waveguide with high optical transmission efficiency is used as an optical propagator probe, a scanning near-field microscope with low optical transmission loss to the microscopic aperture or low optical transmission loss from the microscopic aperture is configured. And high-sensitivity optical characteristics can be measured.

  The scanning near-field microscope according to the seventh idea is characterized in that, in the invention of the fifth idea, the light propagating body is an optical fiber.

  According to the present invention, since an optical fiber with high optical transmission efficiency is used as a light propagator probe, a scanning near-field microscope with low optical transmission loss to a microscopic aperture or low optical transmission loss from a microscopic aperture is configured. And high-sensitivity optical characteristics can be measured.

  Further, the scanning near-field microscope according to the eighth idea is the invention according to the first idea to the third idea, wherein the light propagating body probe holding mechanism on which the light propagating body probe is mounted includes a base material, a piezoelectric element, and an insulating material. It is characterized by a structure in which a film and an electrode plate that is electrically grounded are laminated.

  According to the present invention, since the electrical ground potential required for potential measurement can be ensured only by mounting the light propagator probe on the holding mechanism, the scanning-type near field of view allows accurate and easy surface potential measurement. A microscope can be constructed.

  Further, the scanning near-field microscope according to the ninth idea is the invention of the first idea to the third idea, in which the light propagating probe has a conductive metal film coating at a tip part excluding a transmission port part, The metal film is disposed so as to surround the transmission port portion, and the light propagating body is depressed from an end surface of the metal film.

  According to the present invention, since the dielectric is not disposed at the tip portion of the light propagating probe and the tip portion of the probe is only covered with the metal film, the electrical ground potential can be stabilized, and an accurate surface potential can be obtained. A scanning near-field microscope capable of measurement can be configured.

  Embodiments of a scanning near-field microscope according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a schematic configuration of a scanning near-field microscope according to the first embodiment.

  In FIG. 1, the scanning near-field microscope according to Embodiment 1 includes a light propagating probe 1, a piezoelectric element 2 that vibrates the light propagating probe 1, and an AC voltage that supplies an excitation voltage to the piezoelectric element 2. A source 21, a laser light source 5 for measuring the displacement of the light propagator probe 1 and its photodetector 6, a frequency separation circuit 24 for frequency-separating a signal detected by the photodetector 6, and a laser beam applied to the light propagator probe 1. A laser light source 7 and a laser light introducing optical system 8, a sample stage 4 on which the sample 3 is placed, an XYZ moving mechanism 12 for moving the sample three-dimensionally, a condensing optical system 9, and a reflecting mirror 10, a photodetector 11 for detecting signal light from the sample, an AC voltage source for potential measurement 22 for applying a voltage to the sample, and an offset adjustment circuit 23, the overall scanning control and shape, light, surface potential Such as And a control unit 20 for acquiring items, composed.

  FIG. 4 shows an example of the light propagator probe 1. An optical waveguide 101 is attached to the base 104. The optical waveguide 101 is bent downward in the vicinity of the tip in order to perform scanning control using AFM control. The periphery of the optical waveguide 101 is covered with a metal coating 102 except for the rear end, and a minute opening 103 is formed at the tip. The size of the minute aperture 103 is a size equal to or smaller than the wavelength of the laser beam used, for example, several tens of nm. For example, a silica-based optical waveguide is used as the optical waveguide 101. As for the structure of the optical waveguide, FIG. 4 shows a single-layer structure, but a step index type optical waveguide having a shape in which a core layer having a high optical refractive index is sandwiched by a cladding layer having a low refractive index can also be used. . The thickness of the metal coating 102 is several tens nm to several hundreds nm, and a light reflecting material having high conductivity such as aluminum, chromium, gold, platinum or the like is used as the material. The base 104 is, for example, a silicon substrate or a glass substrate that is generally used as a wafer in a thin film process. In the manufacturing process, the optical waveguide is laminated and patterned, and then elements are separated by etching. The probe has a length of several tens of microns to several hundreds of microns, a thickness of several microns, and a width of several tens of microns to 100 microns. At this time, the spring constant when the light propagator probe 1 is a cantilever is several hundredths of N / m to several N / m, which is equivalent to the spring constant of a general AFM cantilever.

  FIG. 5 shows another example of the light propagator probe 1. The optical fiber 111 is thinned in the vicinity of the tip, and the vicinity of the tip is bent downward in order to perform scanning control using AFM control.

  The periphery of the fiber 111 is covered with a metal coating 112 except for the rear end, and a minute opening 103 is formed at the tip. The size of the minute aperture 103 is a size equal to or smaller than the wavelength of the laser beam used, for example, several tens of nm. As the optical fiber 111, a single mode optical fiber or a multimode optical fiber designed according to the wavelength of the light source to be used is used. The thickness of the metal coating 112 is several tens nm to several hundreds nm, and a light reflecting material having high conductivity such as aluminum, chromium, gold, platinum or the like is used as the material. The diameter of the thinned portion of the optical fiber 111 is about 10 to 60 microns, the length is 0.5 to 3 mm, and the spring constant is several tenths of N / m to several tens of N / m.

  FIG. 7 and FIG. 8 are diagrams showing examples of the light propagating body probe, and show a longitudinal sectional view in the vicinity of the minute opening at the tip. The light propagating body 130 having a large dielectric constant such as an optical waveguide or an optical fiber has a conical shape near the tip. The vicinity of the tip of the light propagating body 130 is covered with a metal film coating 112. A minute opening 103 is formed at the tip. There is no light propagating body 130 at the front end surface where the minute opening 103 is formed, and the light propagating body 130 is depressed from the end surface of the metal film coating 112. That is, there is no dielectric near the minute opening at the tip of the light propagator probe, and only the metal film coating 103 is disposed.

  The light propagator probe shown in FIGS. 7 and 8 is different in the shape of the micro opening 103 at the tip. This difference in shape is caused by a difference in manufacturing method. In the fine aperture shape shown in FIG. 7, the metal film coating 112 is formed on the sharpened light propagating body 130 except for the fine aperture 103 by, for example, rotary vapor deposition, as in the conventional optical fiber probe manufacturing. Thereafter, the metal film coating 112 is used as a mask, and a light propagating body near the tip is isotropically etched through the minute opening 103, whereby a desired shape can be manufactured. In the minute opening shape shown in FIG. 8, the metal film coating 112 is formed on the entire surface including the minute opening near the tip of the sharpened light propagating body 130 by a technique such as vapor deposition, sputtering, or plating. Thereafter, a desired shape can be manufactured by removing the metal film covering of the minute aperture 103 using a focused ion beam.

  According to the structure of the light propagator probe as described above, since the tip of the probe is only coated with a metal film, the electrical ground potential can be stabilized and accurate surface potential measurement can be performed. A microscope can be constructed.

  In FIG. 1, the displacement detection of the light propagator probe 1 shows an optical lever, but other displacement detectors such as a laser interferometer, a piezoelectric sensor, and a capacitance sensor can also be used. The laser light introducing optical system 8 is a lens optical system, an optical fiber optical system, or the like.

  An excitation voltage Vr · sin ωrt corresponding to the resonance frequency of the light propagating probe 1 is applied to the piezoelectric element 2 from the AC voltage source 21. Here, Vr is a voltage amplitude, ωr is a resonance frequency of the light propagating probe, and t is time. The vibration of the light propagator probe 1 is detected by the displacement measurement laser light source 5 constituting the optical lever and its photodetector 6, and using the signal of the frequency ωr component generated by the frequency separation circuit 24, the dynamic mode probe 1. Scanning is controlled by AFM control. The scanning of the sample is performed by the XYZ moving mechanism 12, and the control is performed by the control device 20.

  On the other hand, the light propagating probe 1 is electrically insulated from the piezoelectric element 2 and connected to an electrical ground. That is, the light propagator probe is set to the ground potential. A voltage VACsinωt is applied from the potential measurement AC voltage source 22 to the sample 3 electrically connected to the sample stage 4. At this time, vibration of the frequency ω is generated in the light propagating cantilever according to the potential of the sample surface. The vibration of the frequency ω is separated as a surface potential signal by the frequency separation circuit 24 and transmitted to the control device 20. The control device adjusts the offset voltage of the offset adjustment circuit 23 so that the vibration of the light propagator probe 1 due to the voltage VACsinωt is eliminated. This offset voltage indicates a value obtained by multiplying the potential of the sample surface by -1.

  In the present embodiment, a configuration in which the potential of the light propagating probe 1 is set to an electrical ground potential and an AC voltage for potential measurement is applied to the sample 3 is shown. On the contrary, the potential measurement can be performed even when the sample 3 is set to an electrical ground potential and an AC voltage for potential measurement is applied to the light propagating probe 1.

  Further, the laser beam of the laser light source 7 is applied to the rear end of the light propagator probe 1 using the laser beam introduction optical system 8 while scanning the light propagator probe 1 by dynamic mode AFM control as described above. Introduced. The near-field light is irradiated to the sample from the minute opening at the probe tip, and the laser light transmitted through the sample is detected by the photodetector 11 via the condensing optical system 9 and the reflection mirror 10. FIG. 1 shows a configuration of an illumination mode in which near-field light is irradiated from a minute opening at the tip of the light propagator probe 1, but a structure for detecting near-field light localized on the sample surface through the minute opening (collection mode). It is also possible to employ an illumination / collection mode configuration in which near-field light is irradiated from a minute aperture and signal light from a sample is detected using the same minute aperture.

  According to the configuration of the scanning near-field microscope as described above, it is possible to simultaneously measure the surface potential of the sample in addition to the shape and optical characteristics of the sample surface. It is also possible to measure changes in the sample surface potential due to light irradiation (photostimulation) by comparing scanning data with light irradiation and scanning data without light irradiation.

(Embodiment 2)
FIG. 2 is a block diagram showing a schematic configuration of a scanning near-field microscope according to the second embodiment.

  2, the same components as those in FIG. 1 are denoted by the same reference numerals. The scanning near-field microscope according to the second embodiment includes a light propagating probe 1, a laser light source 5 for measuring displacement of the light propagating probe 1, its photodetector 6, and a signal detected by the photodetector 6 with a frequency. A frequency separation circuit 24 for separating, a laser light source 7 and a laser light introducing optical system 8 for introducing laser light into the light propagating body probe 1, a sample 3 and a sample stage 4 on which the sample is placed, and a sample are moved three-dimensionally. An XYZ moving mechanism 12, a condensing optical system 9, a reflecting mirror 10, a photodetector 11 for detecting signal light from the sample, an AC voltage source for potential measurement 22 for applying a voltage to the sample, and an offset The adjustment circuit 23 includes the entire scanning control and a control device 20 that acquires signals such as shape, light, and surface potential. This embodiment is different from the first embodiment shown in FIG. 1 in that the piezoelectric element 2 is not installed.

  A bias voltage is applied between the light propagator probe 1 and the sample 3 which are electrically grounded. That is, when an AC voltage represented by VAC sin ωt is applied to the sample, the light propagating probe 1 is excited by electrostatic coupling between the tip of the light propagating probe 1 and the surface of the sample 3. The vibration of the light propagator probe 1 detected by the optical lever is frequency separated by the frequency separation circuit 24.

  Here, the term 2ω is the term of the distance between the tip of the light propagator probe 1 and the surface of the sample 3, and the surface of the sample 3 is scanned by controlling the height with an XYZ moving mechanism so that this value is constant. Shape can be obtained.

  On the other hand, the term of frequency ω is a term of the surface potential of the sample. The signal of the frequency ω is separated as a surface potential signal by the frequency separation circuit 24 and transmitted to the control device 20. The control device adjusts the offset voltage of the offset adjustment circuit 23 so that the vibration at the frequency ω is eliminated. This offset voltage indicates a value obtained by multiplying the potential of the sample surface by -1.

  Further, the laser beam of the laser light source 7 is introduced into the rear end of the light propagating probe 1 using the laser beam introducing optical system 8 while scanning the light propagating probe 1 as described above.

  The near-field light is irradiated to the sample from the minute opening at the probe tip, and the laser light transmitted through the sample is detected by the photodetector 11 via the condensing optical system 9 and the reflection mirror 10. FIG. 2 shows an illumination mode configuration that irradiates near-field light from a minute aperture at the tip of the light propagator probe 1, but a configuration that detects near-field light localized on the sample surface through the minute aperture (collection mode). It is also possible to employ an illumination / collection mode configuration in which near-field light is irradiated from a minute aperture and signal light from a sample is detected using the same minute aperture.

  According to the configuration of the scanning near-field microscope as described above, it is possible to simultaneously measure the surface potential of the sample in addition to the shape and optical characteristics of the sample surface. It is also possible to measure changes in the sample surface potential due to light irradiation (photostimulation) by comparing scanning data with light irradiation and scanning data without light irradiation.

(Embodiment 3)
FIG. 3 is a block diagram showing a schematic configuration of a scanning near-field microscope according to the third embodiment.

  In FIG. 3, the same components as those in FIG. A scanning near-field microscope according to Embodiment 3 includes a light propagating probe 1, a piezoelectric element 2 that vibrates the light propagating probe 1, an AC voltage source 21 that supplies an excitation voltage to the piezoelectric element 2, In order to introduce laser light into the optical propagator probe 1, the laser light source 5 for measuring the displacement of the optical propagator probe 1 and its photodetector 6, the frequency separation circuit 24 that frequency-separates the signal detected by the photodetector 6. Laser light source 7 and laser light introducing optical system 8, a modulation device 13 for amplitude-modulating the laser light, a modulation signal generator 15 for giving a modulation signal to the modulation device 13, and a surface using the modulation signal of the laser as a reference signal A phase detector 14 for phase detection of a potential signal, a sample 3 and a sample stage 4 on which the sample is placed, an XYZ moving mechanism 12 for moving the sample in three dimensions, a condensing optical system 9, and a reflecting mirror 10 , A photodetector 11 for detecting signal light from the sample, an AC voltage source for potential measurement 22 for applying a voltage to the sample, and an offset adjustment circuit 23, and the overall scanning control and shape, light, surface potential, etc. And a control device 20 for acquiring a signal. 1 differs from the first embodiment shown in FIG. 1 in that the modulation of the laser beam is performed and the phase detection of the surface potential signal corresponding to the modulation of the laser beam.

  An excitation voltage Vr · sin ωrt corresponding to the resonance frequency of the light propagating probe 1 is applied to the piezoelectric element 2 from the AC voltage source 21. Here, Vr is a voltage amplitude, ωr is a resonance frequency of the light propagating probe, and t is time. The vibration of the light propagator probe 1 is detected by the displacement measurement laser light source 5 constituting the optical lever and its photodetector 6, and using the signal of the frequency ωr component generated by the frequency separation circuit 24, the dynamic mode probe 1. Scanning is controlled by AFM control. The scanning of the sample is performed by the XYZ moving mechanism 12, and the control is performed by the control device 20.

  On the other hand, the light propagating probe 1 is electrically insulated from the piezoelectric element 2 and connected to an electrical ground. That is, the light propagator probe is set to the ground potential. A voltage VACsinωt is applied from the potential measurement AC voltage source 22 to the sample 3 electrically connected to the sample stage 4. At this time, vibration of the frequency ω is generated in the light propagating cantilever according to the potential of the sample surface. The vibration of the frequency ω is separated as a surface potential signal by the frequency separation circuit 24 and transmitted to the control device 20. The control device adjusts the offset voltage of the offset adjustment circuit 23 so that the vibration of the light propagator probe 1 due to the voltage VACsinωt is eliminated. This offset voltage indicates a value obtained by multiplying the potential of the sample surface by -1.

  Further, while the light propagating probe 1 is controlled to be scanned by dynamic mode AFM control as described above, the laser beam of the laser light source 7 is applied to the rear end of the light propagating probe 1 and the modulator 13 and the laser beam introducing optics. Introduced using system 8. The modulation device 13 performs amplitude modulation of the laser beam based on the signal Vo · sinωot from the modulation signal generator 15. The near-field light is irradiated to the sample from the minute opening at the probe tip, and the laser light transmitted through the sample is detected by the photodetector 11 via the condensing optical system 9 and the reflection mirror 10. Since the signal detected by the photodetector 11 is modulated by the modulator 13, the S / N ratio of the signal can be increased by phase detection. FIG. 1 shows a configuration of an illumination mode in which near-field light is irradiated from a minute opening at the tip of the light propagator probe 1, but a structure for detecting near-field light localized on the sample surface through the minute opening (collection mode). It is also possible to employ an illumination / collection mode configuration in which near-field light is irradiated from a minute aperture and signal light from a sample is detected using the same minute aperture.

  On the other hand, the surface potential signal of the frequency separation circuit 24 is divided by the phase detector 14 into a signal at the time of light irradiation and a signal at the time of no light irradiation in the light modulation. Thereby, it is possible to perform surface potential measurement at the time of light irradiation and non-irradiation by one scanning.

  According to the configuration of the scanning near-field microscope as described above, it is possible to simultaneously measure the surface potential of the sample in addition to the shape and optical characteristics of the sample surface. Further, by performing light modulation on a light source for performing light irradiation or light detection, it is possible to simultaneously measure a potential image on the sample surface by light irradiation and non-irradiation.

(Embodiment 4)
FIG. 6 is a diagram showing a schematic configuration of a light propagator probe holding mechanism of the scanning near-field microscope according to the fourth embodiment. In FIG. 6, the light propagator probe holding mechanism of the scanning near-field microscope according to the fourth embodiment includes a substrate 121, a piezoelectric element 2, an insulating film 122, and an electrode plate 123 that is electrically grounded. The light propagation probe 1 is mounted so as to be in contact with the electrode plate 123.

  As the piezoelectric element 2, piezoelectric ceramics generally called bimorph is used. This bimorph has a structure in which a piezoelectric plate is sandwiched between positive and negative electrodes. When the light propagating probe 1 is directly mounted on the bimorph, the potential of the light propagating probe 1 becomes the electrode potential of the bimorph, and accurate surface potential measurement is performed. I can't. In the configuration of FIG. 6, the electrode plate 123 that is electrically grounded through the insulating film 122 is grounded, so that the ground potential can be reliably set just by attaching the light propagating probe.

  According to the light propagator probe holding mechanism of the scanning near-field microscope as described above, it is possible to ensure an electrical ground potential necessary for potential measurement only by mounting the light propagator probe on the holding mechanism. It is possible to construct a scanning near-field microscope in which surface potential measurement is accurate and easy.

  As described above, according to the scanning near-field microscope according to the first concept, the front surface of the light propagating probe and the sample are controlled using the light propagating probe while scanning the sample surface by the dynamic mode AFM technique. In addition to measuring the surface potential from the frequency component by applying a bias voltage between the surfaces, and irradiating near-field light from the minute aperture formed at the tip of the light propagator probe, in addition to the shape and optical characteristics of the sample surface Thus, the surface potential of the sample can be measured simultaneously. It is also possible to measure changes in the sample surface potential due to light irradiation (photostimulation) by comparing scanning data with light irradiation and scanning data without light irradiation.

  Further, according to the scanning near-field microscope according to the second idea, a bias voltage is applied between the tip of the light propagating probe and the sample surface to excite the light propagating probe, and the light propagating probe is calculated from the frequency component of the vibration. By controlling the distance between the tip and the sample surface to obtain the surface shape, measuring the surface potential from another frequency component, and further irradiating near-field light from the microscopic aperture formed at the tip of the light propagator probe, In addition to the shape and optical properties of the sample surface, the surface potential of the sample can be measured simultaneously. It is also possible to measure changes in the sample surface potential due to light irradiation (photostimulation) by comparing scanning data with light irradiation and scanning data without light irradiation.

  Further, according to the scanning near-field microscope according to the third concept, the bias between the tip of the light propagating probe and the sample surface is controlled using the light propagating probe while scanning the sample surface by the dynamic mode AFM technique. In addition to measuring the surface potential from the frequency component by applying a voltage and irradiating near-field light from the microscopic aperture formed at the tip of the light propagator probe, in addition to the shape and optical characteristics of the sample surface, It is possible to measure the surface potential simultaneously. Further, by performing light modulation on a light source for light irradiation or light detection, it is possible to simultaneously measure a potential image on the sample surface by light irradiation and non-irradiation.

  Further, according to the scanning near-field microscope according to the fourth idea, in the invention of the first idea to the third idea, the light propagating probe can be configured as a cantilever made of an optical waveguide layer, and a conventional AFM cantilever is provided. It is possible to give a spring constant equivalent to. Therefore, it is possible to configure a scanning near-field microscope having sufficient sensitivity for surface potential measurement.

  Further, according to the scanning near-field microscope according to the fifth idea, in the inventions of the first idea to the third idea, the light propagating body probe can be composed of a thinned light propagating body, and a conventional AFM cantilever It is possible to give a spring constant equivalent to. Therefore, it is possible to configure a scanning near-field microscope having sufficient sensitivity for surface potential measurement.

  Further, according to the scanning near-field microscope according to the sixth idea, in the invention of the fourth idea, the light propagating body is constituted by a thin film optical waveguide, so that the optical transmission loss to the minute aperture is small or the minute aperture is reduced. Thus, a scanning near-field microscope with low optical transmission loss can be configured, and high-sensitivity optical characteristics can be measured.

  Further, according to the scanning near-field microscope according to the seventh idea, in the invention of the fifth idea, the light propagating body is made of an optical fiber, so that light transmission loss to the minute aperture is small or light from the minute aperture is obtained. A scanning near-field microscope with little transmission loss can be configured, and optical characteristics can be measured.

  Also, according to the scanning near-field microscope according to the eighth idea, in the inventions of the first idea to the third idea, the electric propagator probe is simply mounted on the holding mechanism, and the electrical necessary for potential measurement is obtained. Since the ground potential can be ensured, a scanning near-field microscope can be configured with accurate and easy surface potential measurement.

  Further, according to the scanning near-field microscope according to the ninth idea, in the inventions of the first idea to the third idea, the tip of the light propagating probe is not disposed with a dielectric, and the probe tip is only covered with a metal film. Therefore, it is possible to configure a scanning near-field microscope that can stabilize the electrical ground potential and perform accurate surface potential measurement.

It is a block diagram which shows schematic structure of the scanning near-field microscope which concerns on Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the scanning near-field microscope which concerns on Embodiment 2 of this invention. It is a block diagram which shows schematic structure of the scanning near-field microscope which concerns on Embodiment 3 of this invention. It is a block diagram of the light propagation body probe which concerns on embodiment of this invention. It is a block diagram of the light propagation body probe which concerns on embodiment of this invention. It is a figure which shows schematic structure of the light propagating body probe holding mechanism of the scanning near-field microscope which concerns on Embodiment 4 of this invention. It is a block diagram of the light propagation body probe which concerns on embodiment of this invention. It is a block diagram of the light propagation body probe which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light propagator probe 2 Piezoelectric element 3 Sample 4 Sample stand 5 Displacement measurement laser light source 6 Photo detector 7 Laser light source 8 Laser light introducing optical system 9 Condensing optical system 10 Reflecting mirror 11 Photo detector 12 XYZ moving mechanism 13 Modulation Device 14 Phase detector 15 Modulation signal generator 20 Control device 21 AC voltage source 22 AC voltage source for potential measurement 23 Offset adjustment circuit 24 Frequency separation circuit 101 Optical waveguide 102 Metal coating 103 Micro aperture 104 Base 111 Optical fiber 112 Metal coating 121 Base Material 122 Insulating film 123 Electrode plate 130 Light propagating body

Claims (5)

Comprising a light propagating body probe having a cantilever formed of a dielectric, the distance between the surface or medium surface of the sample to be measured and the tip portion of the optical propagating body probe, the distal end portion of the light propagating body probe to the surface In contrast, the surface is scanned by a two-dimensional scanning means while being vibrated in the vertical direction and brought close to an operating distance where an interatomic force or other interaction force acts, and the surface is scanned by a control means. In the scanning near-field microscope which controls the light propagating body probe along the shape of the surface and performs light irradiation or light detection on the minute region of the surface,
Displacement detecting means for detecting the displacement of the cantilever;
A frequency separation circuit connected to the displacement detection means;
(1) A vibrator composed of a piezoelectric element that vibrates the light propagator probe in a direction perpendicular to the surface, and the vibrator using an AC voltage having a frequency substantially equal to the resonance frequency of the light propagator probe. Voltage application means of the vibrator to be driven;
Electrostatic vibrating means for applying an alternating voltage between the probe tip and the surface in a direction perpendicular to the surface and vibrating the light propagating body probe using an electrostatic force acting on the probe, and the electrostatic Voltage application means of electrostatic vibration means for driving the vibration means with an alternating voltage of a predetermined frequency, or
(2) electrostatic vibrating means for applying an alternating voltage between the probe tip and the surface in a direction perpendicular to the surface and vibrating the light propagating probe by utilizing electrostatic force acting on the probe, and Voltage applying means for electrostatic vibration means for driving the electrostatic vibration means with an alternating voltage of a predetermined frequency,
The displacement detection means separates and outputs the displacement detection signal of the light propagator probe by the frequency separation circuit.
The component detection signal of the frequency of the drive AC voltage of the vibrator in the case of (1), or
A detection signal of a component of a second harmonic of the frequency of the drive AC voltage of the electrostatic vibration means in the case of (2),
Control means for keeping the distance between the tip of the light propagator probe and the surface constant based on:
Based on the frequency component detection signal of the drive AC voltage of the electrostatic vibration means that is separated and output by the frequency separation circuit, the cantilever of the cantilever caused by the AC voltage applied by the voltage application means of the electrostatic vibration means Voltage feedback means for feeding back the voltage so as to eliminate vibration, and
The light propagating probe is bent downward with respect to the cantilever, has a transmission port at a tip portion of the light propagation probe, and a conductive metal film coating at a tip portion excluding the transmission port, The film surrounds the transmission opening and the light propagating body is recessed from the end surface of the metal film,
The light feedback probe tip and either the sample to be measured or the surface of the medium are connected to the ground potential, and the other is connected to the voltage application means, and the voltage feedback means while performing light irradiation or light detection. A scanning near-field microscope, which simultaneously measures the surface potential of a sample based on the voltage fed back in step 1 . The scanning near-field microscope according to claim 1 ,
Modulation means for performing light modulation on a light source for performing light irradiation or light detection on a minute region of the surface;
The vibration detection signal of the cantilever caused by the AC voltage applied by the voltage application means of the vibrator in the case of (1) or the voltage application means of the electrostatic vibration means in the case of (2) , A scanning near-field microscope comprising: phase detection means for detecting a phase corresponding to a modulation signal of the modulation means. The scanning near-field microscope according to claim 1 or 2 ,
After the metal film is formed, the light propagator probe removes the dielectric at the tip of the light propagator probe so that the light propagator is depressed from the end surface of the metal film. Field microscope. The scanning near-field microscope according to claim 3 ,
The light propagator probe is formed by coating a metal film except for the transmission port, the metal film coating is used as a mask, and the light propagator is isotropically etched through the transmission port. A scanning near-field microscope recessed from an end face of the metal film. In the scanning near-field microscope according to any one of claims 1 to 4 ,
The light propagator probe has a portion having an elastic function and a base portion supporting the portion having the elastic function,
A scanning near-field microscope in which the portion having the elastic function is integrally formed with the columnar base portion that supports the portion and has at least a columnar portion, and the outer shape of the columnar portion is narrower than the outer shape of the columnar base portion.

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