JP2022033489A - Infrared measuring device - Google Patents

Abstract

To provide an infrared measuring device that uses an inexpensive and minute infrared light source and has high spatial resolution and high sensitivity.SOLUTION: An infrared measuring device comprises: a nano-carbon light source; a sample stage that holds a sample; a drive mechanism that changes the distance between the sample and the nano-carbon light source with a first angular frequency; an infrared detector that detects light emitted from the nano-carbon light source and transmitting through or reflected on the sample; a signal measuring instrument that measures a near field component included in output from the infrared detector with an angular frequency N times (N is a natural number) the first angular frequency; and an information processing device that processes a measurement result obtained by the signal measuring instrument.SELECTED DRAWING: Figure 4

Description

The present invention relates to an infrared measuring device, and more particularly to an infrared measuring device using a near field generated by a nanocarbon light source.

Infrared spectroscopy represented by Fourier Transform Infrared Spectroscopy (FT-IR) is highly sensitive to functional groups and can identify substances based on existing spectral databases. It is used for controlling substances at the molecular level and observing biomolecules in cells. However, the spatial resolution of infrared spectroscopic analysis is limited to several microns to several tens of microns due to the diffraction limit that light cannot be focused to a size smaller than the wavelength.

In recent years, a new nanoscale infrared spectroscopy called Atomic Force Microscope based Infrared Spectroscopy (AFM-IR) has been developed. The sample is irradiated with infrared laser pulsed light, and infrared absorption by the sample is detected as a change in thermal expansion of the sample. The spot diameter of the infrared laser beam irradiating the sample is about 50 to 100 μm, but since the thermally expanded region is detected by using an AFM probe having a tip diameter of about 20 nm, spatial resolution exceeding the diffraction limit can be obtained.

An infrared analyzer using a fine light source formed of a nanocarbon material has been proposed (see, for example, Patent Document 1).

International Publication No. 2019/176705

AFM-IR requires a tunable infrared laser light source as an external light source. Infrared laser light sources are expensive, and the wavenumber range covered by one tunable infrared laser light source is narrow. In order to cover the wavenumber range of 400 to 4000 cm ^-1 required for general FT-IR measurement, a plurality of tunable infrared lasers having different wavenumber regions must be prepared.

One aspect of the present invention is to provide an infrared measuring device having high spatial resolution and high sensitivity using an inexpensive and fine infrared light source.

In order to achieve the above object, in the embodiment, the distance between the sample and the nanocarbon light source is changed at high speed, and the infrared near-field component is extracted from the light transmitted or reflected through the sample.

In one aspect of the present disclosure, the infrared measuring device is a device.
With nanocarbon light source,
A sample table for holding the sample and
A drive mechanism that changes the distance between the sample and the nanocarbon light source at the first angular frequency.
An infrared detector that detects light emitted from the nanocarbon light source and transmitted or reflected through the sample.
A signal measuring instrument that measures a near-field component contained in the output of the infrared detector at an angular frequency that is N times (N is a natural number) the first angular frequency.
An information processing device that processes the measurement results obtained by the signal measuring instrument, and
Have.

An infrared analyzer with high spatial resolution and high sensitivity using an inexpensive and fine infrared light source can be obtained.

It is a figure which shows an example of the nanocarbon light source used in infrared measurement. It is a figure which shows an example of the nanocarbon light source used in infrared measurement. It is a figure which shows an example of the nanocarbon light source used in infrared measurement. It is a figure of the electromagnetic field generated by a nanocarbon light source. It is a figure which shows the principle of infrared measurement of an embodiment. It is a schematic diagram of the infrared measuring apparatus of 1st Embodiment. It is a figure explaining the lock-in detection of a close field. It is a schematic diagram of the infrared measuring apparatus of 2nd Embodiment. It is a schematic diagram of the infrared measuring apparatus of 3rd Embodiment. It is a figure explaining the linear dichroism imaging. It is a schematic diagram of the infrared measuring apparatus of 4th Embodiment. It is a figure which shows the other configuration example.

In the embodiment, a nanocarbon light source having a nanocarbon material such as graphene or carbon nanotube as a light emitting layer is used. By changing the distance between the nanocarbon light source and the sample at the first angular frequency ωp and extracting the near-field component, the spatial resolution is improved and high-sensitivity measurement is realized. As a good configuration example, the emission (on / off) of the nanocarbon light source is switched at a second angular frequency ωc different from the first angular frequency ωp to further improve the sensitivity of near field detection.

1A to 1C show a configuration example of a nanocarbon light source used in the infrared measuring device of the embodiment. The nanocarbon light source can be miniaturized by microfabrication technology, and can be formed on an arbitrary substrate such as a silicon substrate or a glass substrate. In the embodiment, in order to bring the nanocarbon light source close to the sample, a nanocarbon light source in which the light emitting layer is exposed to the outermost layer is produced.

In FIG. 1A, a nanocarbon light emitting device that operates as a nanocarbon light source 10 is formed on a flat substrate 11A. The substrate 11A may be a silicon substrate having a thermal oxide film formed on its surface, or may be an insulating substrate such as a quartz substrate. The nanocarbon material to be the light emitting layer of the nanocarbon light source 10 may be directly grown on the substrate 11A, or the nanocarbon material grown on another substrate is placed on the substrate 11A by a transfer method or the like. You may.

The light emitting layer of the nanocarbon light source 10 may be exposed to the outside or covered with a very thin protective film having a thickness of about 1 nm to several nm. Electrodes 12 and 13 are connected to the nanocarbon light source 10. When the nanocarbon material is energized and heated via the electrodes 12 and 13, the nanocarbon light source 10 emits infrared light due to heat radiation (blackbody radiation) accompanying the temperature rise of the nanocarbon material. By irradiating the sample 20 with the nanocarbon light source 10 and obtaining the absorption spectrum and the reflection spectrum of the sample 20 having sensitivity to infrared light, it is possible to measure the internal structure of the sample 20 and quantitatively measure it. In the embodiment, the distance between the sample 20 and the nanocarbon light source 10 is changed by the angular frequency ωp, and the near-field component appearing at the angular frequency ωp is used.

In FIG. 1B, the nanocarbon light source 10 is arranged on the substrate 11B whose cross-sectional shape is processed into a trapezoid. The substrate 11B is processed into, for example, a truncated cone, a truncated cone, or the like, and a nanocarbon light source 10, electrodes 12, and 13 are formed on a surface facing the sample 20. The light emitting layer of the nanocarbon light source 10 is exposed toward the sample 20. The relative position of the nanocarbon light source 10 with respect to the sample 20 or the distance between the sample 20 and the nanocarbon light source 10 is changed by the angular frequency ωp, and the measurement is performed using the proximity field component modulated by the angular frequency ωp.

In FIG. 1C, the nanocarbon light source 10 is provided at the tip of the probe 15. 1C (A) is a view showing an example of a usage mode, and (B) is a view seen from the direction A of (A). The probe 15 has a cantilever 16 and a protrusion 17 protruding from the first main surface 161 at the end of the cantilever 16. The probe 15 can be made of silicon with an oxide film, silicon nitride, or the like. A nanocarbon light emitting element that operates as a nanocarbon light source 10 is formed at the tip of the protrusion 17. Electrodes 12a and 13a connected to the nanocarbon light source 10 are formed on the protrusions 17.

Electrodes 12b and 13b are formed on the first main surface 161 of the cantilever 16 and are connected to the electrodes 12a and 13a formed on the protrusion 17, respectively. At the time of use, the probe 15 is arranged with the protrusion 17 facing the sample 20. Due to the vibration of the cantilever 16, the position of the nanocarbon light source 10 with respect to the sample 20 changes at the angular frequency ωp. The second main surface 162 of the cantilever 16 may be used to mechanically or optically detect the position of the nanocarbon light source 10 in the vibration direction, as will be described later.

FIG. 2 is a schematic diagram of an electromagnetic field generated by the nanocarbon light source 10. The infrared light generated from the nanocarbon light source 10 formed on the substrate 11 is not only taken out as a remote field FF and used for measurement, but can also be used for measurement as a near field NF. The remote field light is light that propagates in free space, while the near field light is non-propagated light that is generated only near the interface of the medium.

In the example of FIG. 2, the near-field NF is generated only near the interface of the light emitting layer of the nanocarbon light source 10. As long as the light emitting surface of the nanocarbon light source 10 is exposed so that near-field light can be obtained, the shape of the substrate 11 is not limited, and a flat substrate 11A as shown in FIG. 1A may be used. It may be processed into the shape of the probe 15 as shown in FIG. 1C.

The intensity of the near field decays exponentially depending on the distance from the light source. Unlike the remote field, the near field region depends on the size of the light source, regardless of the diffraction limit. Therefore, the spatial resolution SR is determined by the size of the nanocarbon light source 10. The nanocarbon light source 10 can be miniaturized to the nanometer order by a microfabrication technique such as electron beam lithography. Ultimately, a single single-walled carbon nanotube can be used as a light source, and infrared analysis can be performed with a spatial resolution SR that is orders of magnitude higher than the diffraction limit of "several microns" of conventional infrared spectroscopy. It will be possible.

The principle of near-field NF generated by the nanocarbon light source 10 is different from that of the near-field generated by irradiating a minute hole or the tip of a sharp probe with a laser beam from the outside. The near-field NF generated from the nanocarbon light source 10 is directly generated from the light emitting surface itself of the nanocarbon light source 10.

FIG. 3 is a diagram showing the principle of infrared measurement of the embodiment. The near-field NF generated from the nanocarbon light source 10 can be taken out by bringing the sample 20 and the nanocarbon light source 10 close to each other and converting the near-field light into scattered light. In the example of FIG. 3, the scattered light from the sample 20 is drawn as the light L transmitted through the sample 20 by the transmission type optical system. The light L transmitted through the sample 20 includes remote field light in addition to the near field light scattered or absorbed by the sample 20.

Scattering and absorption of near-field light by the sample 20 may be detected by a reflective optical system. For example, by arranging the nanocarbon light source 10 on the tip or side surface of the probe having an inclined surface, the near-field light scattered or absorbed by the sample 20 can be picked up by the reflected optical system.

The near field NF is a high-intensity electromagnetic field generated at a position sufficiently close to the surface of the nanocarbon light source 10 (usually about a wavelength λ). When the relative position of the nanocarbon light source 10 with respect to the sample 20 is changed with an amplitude of about wavelength λ and an angular frequency ωp, the near-field light converted into scattered light by the sample 20 is also intensity-modulated at the angular frequency ωp. The nanocarbon light source 10 may be vibrated up and down with respect to the sample 20 at an angular frequency ωp, or the sample table holding the sample 20 may be driven with respect to the nanocarbon light source 10 at an angular frequency ωp.

The characteristics and internal structure of the sample 20 can be measured by extracting the near-field light component modulated at the angular frequency ωp from the light transmitted or reflected through the sample 20. A specific configuration example of an infrared measuring device for detecting a near-field component will be described below.

<First Embodiment>
FIG. 4 is a schematic diagram of the infrared measuring device 30A of the first embodiment. The infrared measuring device 30A includes a nanocarbon light source 10, an infrared detector 33, a signal measuring device 34, an information processing device 35, and a drive mechanism 36A. The information processing device 35 is connected to the signal measuring device 34 and the driving mechanism 36A, controls the driving mechanism 36A, analyzes the signal obtained by the signal measuring device 34, and outputs the measurement information.

The nanocarbon light source 10 may be any of the light sources of FIGS. 1A to 1C. The nanocarbon light source 10 is arranged so as to face the sample holding surface (upper surface in FIG. 4) of the sample table 40. An optical path is formed by an optical element 31 between the sample holding surface of the sample table 40 and the infrared detector 33.

In the example of FIG. 4, a parabolic mirror is used as the optical element 31, and a transmission type optical path is formed, but the present invention is not limited to this example. The optical element 31 is not limited to a parabolic mirror, and a plane mirror, an ellipsoidal mirror, or the like may be used, or the optical element 31 may be detected directly by the infrared detector 33 without using a mirror. A reflective optical path may be formed instead of the transmissive optical path. A spectroscope 39 may be provided on the light incident side of the infrared detector 33 to acquire spectral information of the light reflected by the sample 20 directly through the optical element 31 or without using the optical element 31. ..

The infrared detector 33 outputs an electric signal according to the intensity of the received light. The signal measuring device 34 extracts the component of the near field NF from the electric signal input from the infrared detector 33, and supplies the extracted near field component to the information processing apparatus 35. The information processing apparatus 35 analyzes the characteristics, internal configuration, etc. of the sample 20 based on the proximity field component, and outputs the analysis result as measurement information.

The operation of the infrared measuring device 30A at the time of measurement is as follows. Under the control of the information processing apparatus 35, the drive mechanism 36A changes the distance between the nanocarbon light source 10 and the sample 20 at an angular frequency ωp (S1). The plane on which the sample table 40 for holding the sample 20 is arranged is defined as the XY plane, and the height direction orthogonal to the XY plane is defined as the Z direction. The drive mechanism 36A may vibrate the substrate 11 on which the nanocarbon light source 10 is formed in a direction parallel to the Z axis, or may vibrate the sample table 40 in a direction parallel to the Z axis.

When the distance between the nanocarbon light source 10 and the sample 20 changes at an angular frequency ωp, a near-field NF is generated from the nanocarbon light source 10 at an angular frequency ωp (S2). The light L from the sample 20 (transmitted light in the example of FIG. 4) includes near-field light that is modulated by the angular frequency ωp and scattered or absorbed by the sample 20, and remote-field light that has passed through the sample 20. ing.

The light L guided to the infrared detector 33 by the optical element 31 is converted into an electric signal and input to the signal measuring device 34. The signal measuring instrument 34 detects the near-field component contained in the electric signal at an angular frequency N × ωP (N is a natural number) (S3). When the signal measuring instrument 34 is a lock-in amplifier, a signal synchronized with the angular frequency ωP obtained from the drive mechanism 36A or the information processing device 35 may be input to the lock-in amplifier as a reference signal. By locking-in detecting the input electric signal at an angular frequency N × ωp (N is a natural number), only the near-field component can be extracted.

FIG. 5 is a diagram illustrating lock-in detection of a proximity field component. The upper side of FIG. 5 schematically represents the signal input to the signal measuring instrument 34, and the lower side schematically represents the signal for which lock-in is detected. The intensity of the transmitted light signal input to the signal measuring instrument 34 is periodically (at an angular frequency ωp) in the section of only the remote field (FF) and the section of the combined remote field (FF) and near field (NF). )Change. By detecting the lock-in in the cycle of N × ωp (N is a natural number) with the signal measuring instrument 34, only the component of the near field NF can be extracted.

When N is 2 or more, the near field component is detected using a higher frequency. Since the magnitude of the proximity field NF decreases exponentially as the distance from the nanocarbon light source 10 increases, the distance dependence of the scattered light at the angular frequency ωp (dependence on the distance between the nanocarbon light source 10 and the sample 20). G) becomes a non-harmonic vibration. By demodulating the signal from the infrared detector 33 with N × ωp (N = 2, 3, ...) Which is a high-order frequency, the near-field component can be detected with high sensitivity.

Using a higher frequency is a near field when the remote field is also detected by lock-in detection, for example, when the vibration of the nanocarbon light source 10 is large and the remote field also changes due to the vibration. It is effective for improving the extraction accuracy of.

When a lock-in amplifier is used as the signal measuring device 34, a spectrum can be obtained by the lock-in amplifier by arranging a spectroscope 39 such as a monochromator or a Michelson interferometer on the incident side of the infrared detector 33. When a Michelson interferometer is used, a spectrum can be obtained by measuring an interferogram (composite waveform spectrum), which is an interference component that fluctuates due to an optical path difference, and performing a Fourier transform.

As the signal measuring instrument 34, a spectrum analyzer, a power meter, a frequency counter, or the like may be used instead of the lock-in amplifier. Since these signal measuring devices can simultaneously measure signals synchronized with various frequencies, the proximity field component of the angular frequency ωp is extracted, and the modulation component of another frequency is used as in the embodiment described later. Can be detected.

The information processing apparatus 35 analyzes the extracted proximity field component, estimates the characteristics of the sample 20, and outputs the characteristics. For example, the infrared wavelength is based on the absorption spectrum of the sample 20 obtained from the difference or ratio between the intensity of the proximity field generated by the nanocarbon light source 10 and the intensity of the proximity field component extracted by the signal measuring instrument 34. The presence or absence, amount, etc. of a specific cell or molecular structure having absorption sensitivity to light may be specified.

<Second Embodiment>
FIG. 6 is a schematic diagram of the infrared measuring device 30B of the second embodiment. In the second embodiment, the nanocarbon light source 10 is scanned relative to the sample 20 in the XY plane to realize infrared imaging.

The infrared measuring device 30B includes a nanocarbon light source 10, an infrared detector 33, a signal measuring device 34, an information processing device 35, and a drive mechanism 36B. Depending on the function of the signal measuring device 34, the spectrometer 39 may be arranged on the incident surface side of the infrared detector 33. Except for the operation of the drive mechanism 36B, the overall configuration of the device is the same as that of the infrared measuring device 30A of the first embodiment.

The operation of the infrared measuring device 30B at the time of measurement is as follows. Under the control of the information processing apparatus 35, the drive mechanism 36B changes the relative position of the nanocarbon light source 10 in the Z direction with respect to the sample 20 at the angular frequency ωp (S1-1), and nanocarbon in the XY plane. The light source 10 is scanned against the sample 20 (S1-2). The vibration at the angular frequency ωp and the scanning in the XY plane may be controlled independently. For example, the substrate 11 on which the nanocarbon light source 10 is formed may be vibrated in the Z direction to drive the sample table 40 holding the sample 20 in the XY plane.

When the distance between the nanocarbon light source 10 and the sample 20 changes at an angular frequency ωp, a near-field NF is generated from the nanocarbon light source 10 at an angular frequency ωp (S2). The light L from the sample 20 (transmitted light in the example of FIG. 6) includes near-field light that is modulated by the angular frequency ωp and scattered or absorbed by the sample 20, and remote-field light that has passed through the sample 20. ing.

The light transmitted through the sample 20 is converted into an electric signal by the infrared detector 33 and input to the signal measuring device 34. The signal measuring instrument 34 detects the near-field component contained in the electric signal at an angular frequency N × ωP (N is a natural number) (S3). The information processing apparatus 35 maps the absorption spectrum of the sample 20 in the XY plane based on the relative position of the nanocarbon light source 10 with respect to the sample 20 in the XY plane. This enables infrared absorption imaging.

By using the close field, infrared absorption imaging becomes possible with high spatial resolution exceeding the diffraction limit. Since the spatial resolution depends on the size of the nanocarbon light source 10, a high-resolution infrared measurement image can be obtained by forming a very small nanocarbon light source 10 by microfabrication.

<Third Embodiment>
FIG. 7 is a schematic diagram of the infrared measuring device 30C of the third embodiment. In the third embodiment, an infrared near field of polarization is obtained by using a nanocarbon light source 10C made of nanocarbon tubes oriented in a predetermined direction.

The infrared measuring device 30C includes a nanocarbon light source 10C, an infrared detector 33, a signal measuring device 34, an information processing device 35, and a drive mechanism 36C. Depending on the function of the signal measuring device 34, the spectrometer 39 may be arranged on the incident surface side of the infrared detector 33. Except for the use of the nanocarbon light source 10C and the operation of the drive mechanism 36C, the overall configuration of the apparatus is the same as that of the first embodiment and the second embodiment.

The nanocarbon light source 10C has an array of carbon nanotubes oriented in a predetermined direction on the surface 11s of the substrate 11 facing the sample table 40. By growing or arranging the carbon nanotubes in the direction parallel to the facing surface 11s, linear polarization that vibrates in the orientation direction of the carbon nanotubes can be obtained. By growing or arranging the carbon nanotubes in the direction perpendicular to the facing surface 11s, circular polarization or elliptically polarized light depending on the direction of the spiral of the carbon nanotubes can be obtained.

In the example of FIG. 7, the nanocarbon light source 10C that outputs linearly polarized light is used, and the sample 20C having optical anisotropy is measured infraredly by utilizing the near field of linearly polarized light. When the nanocarbon light source 10C emits linearly polarized light, the vibration of linearly polarized light with respect to the sample 20 is generated by rotating the substrate 11 on which the nanocarbon light source 10 is formed or the sample table 40 holding the sample 20 around the Z axis. The direction, that is, the direction of the plane of polarization, can be changed.

The sample 20 having optical anisotropy has a different absorptivity depending on the vibration direction of the incident linearly polarized light. The nanocarbon light source 10 is scanned relative to the sample 20 in the XY plane while the near field of the linear polarization is modulated by the angular frequency ωp, and the sample 20 is scanned again by changing the direction of the linear polarization. Therefore, the anisotropy distribution of the sample 20 can be obtained.

The operation of the infrared measuring device 30C at the time of measurement is as follows. Under the control of the information processing apparatus 35, the drive mechanism 36C changes the relative position of the nanocarbon light source 10C with respect to the sample 20 in the Z direction at the angular frequency ωp (S1-1), and the nanocarbon in the XY plane. The light source 10C is scanned against the sample 20 (S1-2). The vibration at the angular frequency ωp and the scanning in the XY plane may be controlled independently. For example, the substrate 11 on which the nanocarbon light source 10 is formed may be vibrated in the Z direction to drive the sample table 40 holding the sample 20 in the XY plane.

When the distance between the nanocarbon light source 10 and the sample 20 changes at an angular frequency ωp, a linearly polarized near-field NF is generated from the nanocarbon light source 10 at an angular frequency ωp (S2). The light L from the sample 20 (transmitted light in the example of FIG. 7) is linearly polarized near-field light modulated or absorbed by the sample 20 at an angular frequency ωp, and linearly polarized remote light transmitted through the sample 20. Includes field light.

The light transmitted through the sample 20 is converted into an electric signal by the infrared detector 33 and input to the signal measuring device 34. The signal measuring instrument 34 detects the near-field component of linearly polarized light contained in the electric signal at an angular frequency N × ωP (N is a natural number) (S3). The information processing apparatus 35 stores the measurement result in association with the relative position of the nanocarbon light source 10 with respect to the sample 20 in the XY plane.

Next, the drive mechanism 36C rotates the direction or orientation of the nanocarbon light source 10 with respect to the sample 20 by 90 ° under the control of the information processing device 35 (S1-3). The substrate 11 on which the nanocarbon light source 10 is formed may be rotated by 90 ° around the optical axis, or the sample table 40 holding the sample 20 may be rotated by 90 ° around the Z axis.

After rotating the azimuth by 90 °, the drive mechanism 36C changes the relative position of the nanocarbon light source 10C in the Z direction with respect to the sample 20 at the angular frequency ωp (S1-1), while the sample 20 is in the XY plane. The nanocarbon light source 10C is relatively scanned with respect to the above (S1-2). Since the directions of the polarizations of the near-field light incident on the sample 20 are different, an absorption spectrum different from that before the rotation can be obtained. By calculating the difference between the two absorption spectra with the information processing apparatus 35, it is possible to evaluate the positive / negative and magnitude of the linear dichroism and estimate the orientation of the sample 20.

FIG. 8 is a schematic diagram illustrating linear dichroism imaging. The linear dichroism is an optical characteristic caused by the difference in the absorption of a substance with respect to two linear polarizations in which the vibration directions of the electric field vector (or magnetic field vector) of the polarization differ by 90 degrees. As described above, when the sample 20 has optical anisotropy, the absorption rate differs depending on the vibration direction of the incident linearly polarized light.

The signal measuring instrument 34 measures the absorptance rate (m _// , m _⊥ ) of two orthogonal linearly polarized lines with respect to the adjacent field at an angular frequency of N × ωp (N is a natural number). As explained with reference to FIG. 7, the vibration direction of the linearly polarized light is rotated by 90 °, and the vibration is vibrated in the Z direction at the same angular frequency ωp, and the linearly polarized light is applied relative to the sample 20 at the same scanning locus and the same timing. To measure the absorption rates m _// and m _⊥ .

The information processing apparatus 35 calculates the difference (m _// −m _⊥ ) between the two absorption rates at each scanning point. The optical anisotropy of the sample 20 and its distribution can be evaluated depending on whether the magnitude of the difference becomes positive or negative. When the information processing apparatus 35 has a digital image processing function including conversion to an image signal, quantitative and high-resolution linear bicolor imaging is realized by imaging the distribution of measured values. The infrared measuring device 30C can be applied to the evaluation of polymer films and fibers oriented by stretching or the like, the functional evaluation of biological tissues having orientation, and the like.

<Fourth Embodiment>
FIG. 9 is a schematic diagram of the infrared measuring device 30D of the fourth embodiment. In the fourth embodiment, in addition to the vibration of the nanocarbon light source 10 or the sample table 40 at the angular frequency ωp, the nanocarbon light source 10 is switched on and off at a second angular frequency ωc different from ωp.

The infrared measuring device 30D includes a nanocarbon light source 10, an infrared detector 33, a dual mode lock-in amplifier 37 as a signal measuring device, an information processing device 35, and a drive mechanism 36B. Further, the feedback circuit 38 may be provided. The feedback circuit 38 and the information processing device 35 may be integrally configured, or the feedback circuit 38 may be incorporated in the information processing device 35. The spectrometer 39 may be arranged on the incident side of the infrared detector 33. The positional relationship between the nanocarbon light source 10 and the sample 20 and the configuration of the optical path and the like are the same as those in the second embodiment.

In optical measurements such as absorption measurement and spectrum measurement, the measurement intensity and spectrum may drift due to fluctuations in the light source. The nanocarbon light source 10 can be modulated at an ultra-high speed of about 10 GHz, and can modulate the light emission itself at an angular frequency ωc higher than the angular frequency ωp generated in the near field. By arranging the nanocarbon light source 10 and the sample 20 in close proximity, the generation of the near field NF is modulated by the angular frequency ωp, and the emission is modulated by the angular frequency ωc, the light transmitted (or reflected) through the sample 20 is obtained. It contains modulation components at two angular frequencies.

In the configuration example of FIG. 9, the transmitted light of the sample 20 is received by the infrared detector 33, and the signal is measured at the angular frequencies ωp and ωc by the dual mode lock-in amplifier 37 equipped with the dual reference mode. Instead of the dual mode lock-in amplifier 37, a signal measuring instrument such as a spectrum analyzer, a power meter, or a frequency counter may be used. When these signal measuring instruments are used, signals synchronized with a plurality of frequencies can be measured at the same time, so that the near-field component having an angular frequency ωp and the remote field component having an angular frequency ωc can be measured at the same time.

By correcting the drift caused by the fluctuation of the nanocarbon light source 10 with the reference light (remote field light) having an angular frequency ωc, highly sensitive measurement in which the influence of the fluctuation is suppressed becomes possible. By modulating the light emission itself of the nanocarbon light source 10 with the angular frequency ωc, the modulation near field of ωc that appears in the period of ωp and the modulation remote field light of ωc (reference light), or the ratio or difference between these two is highly sensitive. It can be measured with.

In order to realize the function of the infrared measuring device 30D in a general optical system, the light emitted from the light source is split by a beam splitter, and each light is separately modulated by two light choppers having different periods. A complicated optical system is required in which two lights are recombined by a beam splitter. In addition, it is difficult to perform ultra-high-speed on / off modulation and on / off modulation at an arbitrary frequency with a normal infrared laser light source. By using the nanocarbon light source 10, a near field is generated from the light source itself at an angular frequency ωp, and high-speed on / off modulation is applied to perform synchronous detection on one optical axis without optical branching or combined wave. It will be possible.

In order to measure the ratio of the ωp component and the ωc component at the same time with the dual mode lock-in amplifier 37 and other signal measuring instruments, the signal representing the fractional ratio of the two angular frequency components, the difference frequency, and the sum frequency The signal may be measured. The information processing apparatus 35 may correct the intensity change of the nanocarbon light source based on the measurement results at the angular frequencies ωp and ωc to increase the measurement sensitivity. Alternatively, the intensity of the nanocarbon light source 10 may be stabilized by negatively feeding back a signal having an angular frequency ωc by the feedback circuit 38. Harmonics of angular frequencies ωc and ωp (N × ωc and N × ωp, N is an integer of 2 or more) may be used to further improve the sensitivity.

The operation of the infrared measuring device 30D at the time of measurement is as follows. Under the control of the information processing apparatus 35, the drive mechanism 36B changes the relative position of the nanocarbon light source 10 in the Z direction with respect to the sample 20 at the angular frequency ωp (S1-1), and nanocarbon in the XY plane. The light source 10C is scanned against the sample 20 (S1-2). At this time, the nanocarbon light source 10 emits light at an angular frequency ωc different from ωp (S2-1), and a near field modulated by ωc is generated at an angular frequency ωp (S2-2).

The light L from the sample 20 (transmitted light in the example of FIG. 9) includes ωc-modulated near-field light scattered or absorbed by the sample 20 and ωc-modulated remote-field light transmitted through the sample 20. There is. Of these, the modulated near-field light of ωc is generated at the angular frequency ωp.

The light transmitted through the sample 20 is converted into an electric signal by the infrared detector 33 and input to the dual mode lock-in amplifier 37. The dual mode lock-in amplifier 37 measures near-field light at angular frequencies ωc and ωp with respect to the input electric signal (S3D). Alternatively, the ratio of ωc to ωp, the sum frequency, and the difference frequency may be measured. Modulated remote field light of ωc may be used as reference light. The information processing apparatus 35 stores the measurement result of the dual mode lock-in amplifier 37 in association with the XY coordinates on the sample 20. In the feedback circuit 38, the intensity of the measured near-field light of modulation of ωc may be negatively fed back to the nanocarbon light source 10 to stabilize the intensity of the nanocarbon light source 10 (S4).

When the information processing apparatus 35 has a digital image processing function including conversion into an image signal, imaging of the sample 20 becomes possible. By imaging the distribution of the absorbance and the difference in absorbance of the sample 20, quantitative and high-resolution linear dichroic imaging is realized. In the fourth embodiment, since the intensity of the nanocarbon light source 10 is stable, high-resolution and high-precision infrared measurement of the sample 20 becomes possible by utilizing the near field.

<Fifth Embodiment>
FIG. 10 is a schematic diagram of the infrared measuring device 30E according to the fifth embodiment. In the fifth embodiment, AFM-IR is combined with the measurement of the sample 20 using the near-field light to improve the measurement accuracy of the sample 20.

In AFM-IR, the thermal expansion of the sample 20 due to infrared absorption is observed by AFM, and a two-dimensional image corresponding to infrared absorption is obtained. The distribution of the infrared absorption characteristics by the sample 20 is imaged by using the deflection of the cantilever due to the van der Waals force acting between atoms or molecules.

The infrared measuring device 30E includes a nanocarbon light source 10, an infrared detector 33, a signal measuring device 34, an information processing device 35, a drive mechanism 36B, a position measuring optical system 51, and a position measuring device 55. .. As the nanocarbon light source 10, a probe light source provided at the tip of the probe 15 is used as shown in FIG. 1C. Except for the position measuring optical system 51 and the position measuring device 55, the configuration and method of infrared measurement using near-field light are the same as those of the infrared measuring device 30B of the second embodiment. The measurement of the surface shape of the sample 20 by AFM-IR may be combined with the infrared measuring device 30C of the third embodiment or the infrared measuring device 30D of the fourth embodiment.

The position measurement optical system 51 includes an external laser light source (denoted as “LD” in the figure) 511, optical elements 512 and 513, and a photodetector 514. The sample 20 absorbs infrared light when irradiated with the nanocarbon light source 10 at the tip of the probe 15. The absorbed light energy is converted into heat energy, and the sample 20 thermally expands. As a result, the cantilever 16 bends, and the height position (position in the Z direction) of the probe 15 with respect to the sample 20 changes. The displacement of the probe 15 in the Z direction correlates with the amount of infrared light absorbed. Due to the thermal expansion of the sample 20, the center position of the vibration of the probe vibrating at ωp changes, and the displacement in the height direction can be detected, so that the infrared absorption that correlates with the thermal expansion can be measured. In addition to directly measuring the height change due to thermal expansion, thermal expansion may be detected and infrared absorption may be measured by measuring the phase change or the resonance frequency change of the vibrating probe.

The position measurement optical system 51 detects the displacement of the probe 15 in the Z direction by utilizing the light reflection on the second main surface 162 of the cantilever 16 of the probe 15. The detection result, i.e. the output of the photodetector 514, is connected to the input of the position measuring instrument 55. The position measuring instrument 55 is composed of, for example, a preamplifier and a lock-in amplifier, and measures the amount of displacement in the Z direction from the detection result of the photodetector 514 (S5). The measured displacement in the Z direction is supplied to the information processing apparatus 35 and used for analysis and imaging corresponding to infrared absorption.

In FIG. 10, the deflection (displacement) of the probe 15 is detected by the optical lever method, but it may be detected by the self-detection method using the piezo strain resistance. When the nanocarbon light source 10 is arranged at the tip of the protrusion 17 of the probe 15 as shown in FIG. 1C, the probe 15 is operated in a non-contact mode in which a constant distance is maintained between the surface of the sample 20 and the tip of the probe 15. Displacement in the Z direction may be detected. When the nanocarbon light source 10 is formed on the side surface of the protrusion 17, a contact mode or a tapping mode may be used.

As shown in FIG. 10, instead of directly measuring the displacement of the probe 15, information such as the amplitude, phase, and frequency due to the deflection of the probe 15 may be detected. These information may be converted into height information by the information processing apparatus 35 to generate an infrared absorption image.

The final infrared absorption distribution may be generated by averaging the infrared measurement result by the signal measuring device 34 and the infrared measurement result by the position measuring device 55, or one measurement data may be used as the measurement data of the other. It may be used for correction.

By using the probe-type nanocarbon light source 10, the thermal expansion due to the absorption of infrared light and the displacement of the probe 15 in the Z direction are directly linked, and high-precision measurement and imaging are realized. When the displacement of the cantilever 16 due to the thermal expansion of the sample 20 is combined with the fourth embodiment, the nanocarbon light source 10 is on / off-modulated at the angular frequency ωc, and the position measuring instrument 55 thermally expands in synchronization with the ωc. The signal may be measured.

Although the present invention has been described above based on the specific embodiment, the present invention is not limited to the above-mentioned configuration example. An infrared measurement result may be transmitted to a server or the cloud by using a mobile terminal such as a smartphone as the information processing device 35. Since the intensity of the nanocarbon light source 10 can be adjusted by voltage control, infrared light having an appropriate intensity may be irradiated depending on the type of the sample 20.

Vibration of the nanocarbon light source at the angular frequency ωp, on / off modulation at the angular frequency ωc, emission intensity of the light source, etc. may be controlled by an integrated circuit for light source control provided separately from the information processing apparatus 35. ..

Instead of the linearly polarized nanocarbon light source 10C, a nanocarbon light source that emits circularly polarized light or elliptically polarized light may be used. Circularly polarized light corresponds to a special case of elliptically polarized light (circularly polarized light having the same amplitude in each direction). Therefore, the term elliptically polarized light below includes circularly polarized light. A nanocarbon light source (first light source) that emits left elliptically polarized light and a nanocarbon light source (second light source) that emits right elliptically polarized light may be arranged adjacent to each other. A first light source and a second light source can be obtained by producing nanocarbon light sources from carbon nanotubes having a clockwise spiral structure and carbon nanotubes having a counterclockwise spiral structure, respectively.

After turning on one light source and scanning the sample 20, the other light source is turned on and the sample 20 is rescanned with the same trajectory. The signal measuring instrument 34, for example, measures the first proximity field component from the irradiation result of the sample by the first light source, and then measures the second proximity field component from the irradiation result of the sample by the second light source. You may. For example, the signal measuring instrument 34 may measure the absorption rate mL of the sample 20 with respect to the left circular polarization, and then measure the _absorption rate _mL of the sample 20 with respect to the right circular polarization. The information processing apparatus 35 may calculate the difference in absorption rate ( _mL −m _R ) and specify the distribution of chirality of the molecule by the positive or negative of the difference.

In either case, since the sample 20 can be directly irradiated with infrared light from the nanocarbon light source 10, the near field can be measured with high sensitivity as compared with the case where an external infrared laser is used.

10, 10C Nanocarbon light source 11, 11A, 11B Substrate 12, 13 Electrode 15 Probe 16 Cantilever 161 First main surface 162 Second main surface 17 Protrusion 20 Sample 30A, 30B, 30C, 30D, 30E Infrared measuring device 31 Optical element 33 Infrared detector 34 Signal measuring instrument 35 Information processing device 36, 36A, 36B Drive mechanism 37 Dual mode lock-in amplifier 38 Feedback circuit 39 Spectrometer 40 Sample stand 51 Position measuring optical system 55 Position measuring instrument (second measurement) vessel)
FF Remote field NF Proximity field L Light (from sample)

Claims (9)

With nanocarbon light source,
A sample table for holding the sample and
A drive mechanism that changes the distance between the sample and the nanocarbon light source at the first angular frequency.
An infrared detector that detects light emitted from the nanocarbon light source and transmitted or reflected through the sample.
A signal measuring instrument that measures a near-field component contained in the output of the infrared detector at an angular frequency that is N times (N is a natural number) the first angular frequency.
An information processing device that processes the measurement results obtained by the signal measuring instrument, and
Infrared measuring device with. The infrared measuring device according to claim 1, wherein the signal measuring device uses a signal synchronized with the drive signal of the drive mechanism as a reference signal. The nanocarbon light source emits linearly polarized light and emits linearly polarized light.
The drive mechanism is such that after the sample is irradiated by the nanocarbon light source and the proximity field component is measured by the signal measuring instrument, the sample table or the nanocarbon light source is placed around an axis perpendicular to the sample table 90. ° Rotate,
The nanocarbon light source re-irradiates the sample in the state after rotation.
The infrared measuring device according to claim 1 or 2. The nanocarbon light source includes a first light source that emits right elliptically polarized light and a second light source that emits left elliptically polarized light.
The signal measuring instrument measures the first proximity field component from the irradiation result of the sample by the first light source, and measures the second proximity field component from the irradiation result of the sample by the second light source.
The infrared measuring device according to claim 1 or 2. The nanocarbon light source is on / off modulated at a second angular frequency different from the first angular frequency.
The signal measuring instrument has an angular frequency (N is a natural number) that is N times the first angular frequency and an angular frequency that is N times (N is a natural number) the second angular frequency. Measure,
The infrared measuring device according to any one of claims 1 to 4. The information processing apparatus has a measurement result at an angular frequency N times the first angular frequency (N is a natural number) and a measurement result at an angular frequency N times the second angular frequency (N is a natural number). To correct the intensity change of the nanocarbon light source based on
The infrared measuring device according to claim 5. A feedback circuit that negatively feeds back the measurement result at an angular frequency N times the second angular frequency (N is a natural number) to the nanocarbon light source.
Further, the intensity of the nanocarbon light source is maintained by the negative feedback.
The infrared measuring device according to claim 5. The drive mechanism scans the nanocarbon light source relative to the sample.
The information processing apparatus produces an infrared absorption distribution of the sample.
The infrared measuring device according to any one of claims 1 to 7. A second measuring instrument that measures the thermal expansion generated in the sample by irradiation with the nanocarbon light source,
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The information processing apparatus analyzes the characteristics of the sample based on the measurement result of the signal measuring device and the measurement result of the second measuring device.
The infrared measuring device according to any one of claims 1 to 7.

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