JP2008082753A - Photoluminescence measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily evaluate the uniformity/non-uniformity of the distribution of carbon nanotubes (CNT) of a specific structure with respect to a membrane like sample in which carbon nanotubes (CNT) are dispersed. <P>SOLUTION: A sample stage 12 for holding the sample 13 is made movable in two axial directions of an X-axis and a Y-axis and the intensities of the photoluminescence (PL) of respective sections are measured while stepwise altering an exciting light irradiation position over the whole of the sample 13. With respect to one section, data including an exciting wavelength, a PL wavelength and PL intensity as dimensions is collected to preserve the data of all sections by a five-dimensional data collection part 22. A chiral index conversion part 23 converts a combination of the exciting wavelength and the PL wavelength to a chiral index for characterizing CNT. A mapping image forming part 24 forms a mapping image for setting vertical and lateral axes as a measuring position and displaying the PL intensity as a contour line to display it on a display part 27. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photoluminescence measuring apparatus that measures photoluminescence emitted from a sample in response to irradiation of excitation light, and more particularly, a photoluminescence that is particularly useful for evaluating the presence or distribution state of carbon nanotubes in a sample. The present invention relates to a luminescence measuring device.

  Single carbon nanotubes have a structure in which a single net-like sheet (graphene sheet) connected with a carbon six-membered ring structure is rounded into a cylindrical shape, but the physical properties differ greatly depending on the roundness (chirality). For example, when carbon six-membered rings are arranged along the axis of the tube, it shows the characteristics as a metal, and when carbon six-membered rings are arranged in a spiral around the axis, the characteristics as a semiconductor are shown. Show. Therefore, it is important to examine the chirality in evaluating the carbon nanotube, and it is necessary to examine the chirality distribution in order to grasp the characteristics of the sample containing the carbon nanotube. For the purpose of measuring such chirality distribution, a near-infrared photoluminescence measuring device using fluorescence spectroscopy has been developed (see Non-Patent Document 1, for example).

  A conventional fluorescence spectroscopic measurement optical system used for such an apparatus is disclosed in, for example, Patent Document 1. That is, solid light in which white light emitted from a xenon lamp, which is a light source, is extracted by wavelength dispersion using an excitation-side spectroscope and held in a cuvette cell or sample holder containing a liquid sample set in a sample chamber. Irradiate the center of the sample. Photoluminescence by fluorescence, phosphorescence, etc. emitted from the sample by this excitation light irradiation is incident on a fluorescence side spectrograph disposed at a position of about 90 ° with respect to the incident optical axis of the excitation light, and is wavelength-dispersed. The intensity is detected for each wavelength.

  However, in such an optical system, only photoluminescence obtained by exciting only a part of the sample can be measured. In the case of a device such as a thin film prepared by synthesizing or synthesizing carbon nanotubes in a carrier, carbon nanotubes with different structures may be distributed side by side, so only one part of the sample is measured. If the chirality distribution is evaluated based on the result, accuracy will be lost. For these reasons, there is a strong demand for an apparatus that can evaluate and confirm the uneven distribution of dispersed carbon nanotubes on a device.

JP 2001-83093 A Watanabe, Osumi, Ikeda, Sasayama, Nakagawa, “Development of Near-Infrared Photoluminescence Spectrometer”, Fullerene Nanotubes Study Group, 29th Fullerene Nanotubes General Symposium Lecture Proceedings, July 25, 2005

  The present invention has been made in view of these problems, and its main object is to provide a photoluminescence measuring apparatus that can easily evaluate the uniformity / non-uniformity of the distribution of substances contained in a sample. It is in. Another object of the present invention is to provide a photoluminescence measuring apparatus capable of presenting the uniformity / non-uniformity of such a material distribution to a user in an easy-to-understand manner.

In order to solve the above-mentioned problems, the present invention provides an irradiation unit that irradiates a sample with excitation light having a predetermined wavelength, and a detection unit that detects the intensity of photoluminescence emitted from the sample in response to the excitation light irradiation. In a photoluminescence measuring device comprising:
a) sample moving means for moving the sample two-dimensionally so that the irradiation position of the excitation light on the sample can be changed;
b) Based on the photoluminescence intensity detected by the detecting means each time the excitation light irradiation position on the sample is changed by the sample moving means, the uniformity of the two-dimensional presence / absence of the contained substance in the sample / Processing means for creating information reflecting non-uniformity;
It is characterized by having.

  In the photoluminescence measuring apparatus according to the present invention, for example, the sample moving means includes a sample holding unit for holding a flat or thin film sample in a biaxial direction (X-axis direction, Y-axis) orthogonal to each other within the spreading surface of the sample. It is possible to provide a moving mechanism that moves each in the direction). When the spot of excitation light irradiated on the sample by the irradiation means has a substantially rectangular shape with predetermined lengths d1 and d2 in the X-axis direction and the Y-axis direction, the moving mechanism moves the sample holder in the X-axis direction and Y If the d1 and d2 can be moved stepwise in the axial direction, the photoluminescence intensity can be measured for the entire two-dimensional surface of the sample without omission.

  For example, when a sample including a single carbon nanotube is used as a measurement object, it is known that carbon nanotubes having different structures and characteristics each have a photoluminescence intensity peak in a combination of a specific excitation wavelength and a photoluminescence wavelength. Therefore, by scanning the wavelength of the excitation light and examining the combination of the excitation wavelength and the photoluminescence wavelength at which a photoluminescence intensity peak occurs, the carbon nanotubes present in the measurement range (excitation light irradiation range) on the sample You can know the kind of. That is, the processing means moves the sample by the sample moving means as described above and, based on the data obtained by repeating the above measurement while scanning the excitation light irradiation position on the sample, the processing means It is possible to create information reflecting the distribution status of the types of carbon nanotubes, that is, uniformity / non-uniformity.

  In general, the structure and characteristics of carbon nanotubes are represented by chiral indices (n, m). Therefore, in one embodiment of the photoluminescence measuring apparatus according to the present invention, the processing means scans the wavelength of the excitation light, thereby measuring position information on the sample (for example, positions in the X-axis direction and the Y-axis direction), Collects data that combines excitation wavelength, photoluminescence wavelength, and photoluminescence intensity, converts the combination of excitation wavelength and photoluminescence wavelength into a chiral index that characterizes carbon nanotubes, and creates a photo on the sample for each chiral index. It can be set as the structure which produces the image information which shows distribution of luminescence intensity | strength.

  In this configuration, the combination of the excitation wavelength and the photoluminescence wavelength is uniquely converted into a corresponding chiral index in the processing means. Then, for each chiral index, that is, for each type of carbon nanotube (difference in structure and characteristics), image information representing the distribution of the photoluminescence intensity on the sample itself or the distribution of the index converted from the intensity is created, This is displayed to the user by displaying it on the screen of the display unit, for example. As described above, since the chiral index indicates the structure of the single carbon nanotube, the user can easily confirm the distribution state of the single carbon nanotube dispersed in the sample based on the display information.

  As described above, according to the photoluminescence measuring apparatus according to the present invention, not only a part of a sample having a certain size and spread, but also the distribution state of contained substances such as carbon nanotubes in the whole or a desired range. It is possible to know, and it is possible to easily evaluate whether the substance is distributed uniformly, whether it is distributed to a specific site, or the like. In particular, according to the configuration of the above-described embodiment of the present invention, the distribution state of each type of single carbon nanotube can be confirmed at a glance, and thus, for example, the fabricated device can be evaluated easily and efficiently.

  Hereinafter, an embodiment of a photoluminescence measuring apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a main part of the photoluminescence measuring apparatus according to the present embodiment. White light emitted from the light source unit 10 including a xenon lamp is wavelength-dispersed by the excitation-side spectroscope 11, and light having a specific wavelength is selected and irradiated to the sample 13 held on the sample stage 12 as excitation light. (Corresponding to the irradiation means in the present invention). The wavelength of the light extracted by the excitation-side spectroscope 11 can be scanned within a predetermined wavelength range λ1 to λ2 in accordance with a command from the control unit 25. Here, the sample 13 is assumed to be a thin film device in which single carbon nanotubes are dispersed, but is not limited thereto.

  Photoluminescence generated by fluorescence or phosphorescence generated from the sample 13 in response to the excitation light irradiation is introduced into the fluorescence-side spectroscope 14, wavelength-dispersed, and incident on the detector 15. Here, the detector 15 has a structure in which a large number of light receiving elements are arranged in an array. Dispersed light in a predetermined wavelength range derived from photoluminescence is detected all at once, and a detection signal corresponding to the intensity for each wavelength is generated. Is output.

  The sample stage 12 has a structure that can move in two directions, ie, an X axis and a Y axis that are orthogonal to each other. The stage X axis drive unit 16 and the stage Y axis drive unit 17 (including a drive source such as a stepping motor) It corresponds to the sample moving means in the present invention) and is moved according to the command of the control unit 25. Since the position of the excitation side spectroscope 11 is fixed and the irradiation position of the excitation light is determined, there are two regions where the excitation light hits the sample 13 by moving the sample stage 12 in the X-axis and Y-axis directions. Move dimensionally.

  A detection signal from the detector 15 is converted into digital data by the A / D converter 20 and input to the data processing unit 21. The data processing unit 21 includes, as functions, a five-dimensional data collection unit 22, a chiral index conversion unit 23, and a mapping image creation unit 24. Data and results obtained by these units are displayed on the screen of the display unit 27 as necessary. Is displayed. The data processing unit 21 and the control unit 25 that controls the entire system can be realized by a personal computer (PC) 28, and the function is executed by executing dedicated control / processing software installed in the PC 28. Can be realized.

  FIG. 2 is a detailed optical path configuration diagram of the photometry system including the excitation side spectroscope 11 and the fluorescence side spectroscope 14. Light emitted from a xenon lamp (not shown) is collimated by a collimating lens and is introduced from the right side of FIG. 2, collected by the lens 30, passes through the slit 31, passes through the mirror 32, the first diffraction grating 33, and the toroidal. Wavelength dispersion is performed by a double monochromator comprising a mirror 34, a slit 35, and a second diffraction grating 36. Then, light having a specific wavelength passes through the slit 37 and is irradiated as excitation light to the sample 13 set on the sample stage 12 through the mirror 38 and the toroidal mirror 39. An opening image of the slit 37 is projected onto the sample 13, and the irradiation area of the excitation light is rectangular. The second diffraction grating 36 can be rotated, and the wavelength of the light reaching the opening of the slit 37 is changed by this rotation, whereby the wavelength scanning of the excitation light is achieved.

  Photoluminescence emitted from the sample 13 upon irradiation with the excitation light is collected by the toroidal mirror 40, passes through the two mirrors 41 and 42, and then the toroidal mirror 43, mirror 44, slit 45, mirror 46, and diffraction grating 47. And wavelength dispersion by a polychromator comprising a mirror 48. The dispersed light is condensed in a direction orthogonal to the paper surface by the cylindrical lens 49 and is incident on the detector 15 while maintaining the dispersed state. For example, an indium gallium arsenide (InGaAs) array detector can be used as the detector 15.

  FIG. 3 is a schematic perspective view of the sample stage 12. The movable part 121 that holds the sample 13 can move linearly with respect to the fixed part 122 in two axial directions of the X axis and the Y axis along a guide (not shown). The thin film sample 13 is held by being pressed against the movable portion 121 by the urging force of the leaf spring 123, and the surface of the sample 13 is irradiated with excitation light substantially perpendicularly.

  FIG. 4 is a plan view showing the entire measurement range of the sample 13. The excitation light irradiation range on the sample 13 is a rectangular shape of d1 × d2, and the sample 13 is considered to be partitioned in a lattice shape with this d1 × d2 as the size of one partition. That is, the movable part 121 of the sample stage 12 is moved stepwise in the X-axis direction and the Y-axis direction so that excitation light is irradiated for each section, so that the entire measurement range is covered without omission. Photoluminescence can be measured. Each section is expressed by address coordinates [x, y].

  Next, the procedure for measuring the photoluminescence of the entire sample in this apparatus will be described with reference to the flowchart of FIG.

  When the measurement is started, the control unit 25 sends a command to the drive units 16 and 17 so that the sample 13 is set at the initial position, and in response to this, the excitation light is sent to the section [0, 0] on the sample 13. The movable part 121 of the sample stage 12 is moved so as to hit (step S1). In this state, the excitation-side spectroscope 11 is set so that light of the lower limit wavelength λ1 (or may be the upper limit wavelength λ2) of the excitation wavelength range λ1 to λ2 is extracted based on the command of the control unit 25 and the excitation light is sampled. 13 is irradiated (step S2). The excitation light hits the section [0, 0] on the sample 13 (see FIG. 4), and photoluminescence is emitted from the range, and its intensity spectrum (photoluminescence wavelength (hereinafter referred to as PL wavelength) -photoluminescence intensity (hereinafter referred to as PL intensity). Is detected by the detector 15. In practice, the PL intensity is obtained by continuing to apply excitation light for the integration time designated for each excitation wavelength and accumulating charge signals by photoluminescence obtained correspondingly (step S3).

  When the measurement for one excitation wavelength is completed, it is determined whether or not the excitation wavelength is the upper limit wavelength λ2 (the lower limit wavelength λ1 when the upper limit wavelength λ2 is set in step S2) (step S4), and the upper limit wavelength λ2 is set. If not, the excitation wavelength is changed by a predetermined wavelength step width Δλ (step S5), and the process returns to step S3. Then, as described above, the section [0, 0] on the sample 13 is irradiated with excitation light, and the PL intensity after changing the excitation wavelength is measured. Steps S3 → S4 → S5 are repeated, and when the excitation wavelength reaches the upper limit wavelength λ2, the process proceeds from step S4 to S5, and it is determined whether or not the sample 13 is at the final position.

  Here, the section [xp, yq] on the sample 13 in FIG. 4 is set as the final position, and when the measurement of the photoluminescence in this section is completed, the entire measurement is completed. If the measurement position on the sample 13 has not reached the final position, the movable unit 121 of the sample stage 12 is moved in the X-axis direction, the Y-axis direction, or both by giving commands to the drive units 16 and 17 as described above. By moving, the excitation light irradiation position on the sample 13 is moved to the next section (step S7), and the process returns to step S2. As long as the photoluminescence measurement is performed for all the sections shown in FIG. 4, the moving procedure of each section is arbitrary. In any case, by repeating the processes of steps S2 to S7, the photoluminescence as described above can be measured in each section.

  Data obtained by repeating steps S3 to S5 described above is data having three dimensions of an excitation wavelength, a PL wavelength, and a PL intensity. Since Y-axis direction addresses 0 to yq (or X-axis coordinates, Y-axis coordinates) are added, the data has five dimensions. That is, by the photoluminescence measurement as described above, the data processing unit 21 collects and stores data having these five dimensions by the five-dimensional data collection unit 22.

  It is known that there are several types of single carbon nanotubes included in the sample 13 to be measured, which have different chiralities, and a PL intensity peak can be observed in each combination of a specific excitation wavelength and a PL wavelength. Therefore, for example, as shown in FIG. 6 (a), a three-dimensional graph having the excitation wavelength on the vertical axis, the PL wavelength on the horizontal axis, and the PL intensity on the axis perpendicular to the paper surface can be created for each section. . Further, focusing on a specific excitation wavelength, as shown in FIG. 6B, a two-dimensional graph can be created with the PL intensity on the vertical axis and the PL wavelength on the horizontal axis.

  The difference in structure and characteristics of single carbon nanotubes is defined by the chiral index (n, m) which is an index of chirality. That is, the combination of the excitation wavelength and the PL wavelength and the chiral index have a one-to-one correspondence. For example, FIG. 7 shows a three-dimensional graph as shown in FIG. 6 (a) created based on the actual measurement results. When a specific single carbon nanotube is present in the figure, the PL intensity peak is indicated at the coordinates indicated by a circle. Indicates that exists. For this reason, the combination of the excitation wavelength and the PL wavelength can be replaced with a chiral index, and the chiral index conversion unit 23 performs such conversion to obtain the chiral index, the X-axis direction address, the Y-axis direction address, and the PL intensity. , It is converted to data with the dimension. In the case of evaluation of single carbon nanotubes, it is easier to handle the data using the chiral index, so it is preferable to store the converted data again.

  The mapping image creation unit 24 organizes data having dimensions of the X-axis direction address, the Y-axis direction address, and the PL intensity for each chiral index, and the horizontal axis indicates the X-axis direction address and the vertical axis indicates the Y-axis direction address. Then, a mapping image corresponding to the measurement range of the sample 13 is created so that the PL intensity is displayed in contour lines, shades, or different colors. FIG. 8 is an example of the mapping image created in this way. According to this mapping image, it is possible to confirm at a glance how single carbon nanotubes having an arbitrary chiral index are distributed over the entire measurement range of the sample 13, and single carbon nanotubes having a specific structure can be confirmed. Can be easily evaluated.

  Specifically, an operator that can input or select a chiral index to be displayed is provided on an operation window displayed on the screen of the display unit 27, and when the user sets a chiral index from the operation unit 26, a mapping image is created. The unit 24 creates a mapping image of the designated chiral index based on the data converted by the chiral index conversion unit 23. At that time, the PL intensity is normalized, and the maximum value of the intensity is set to red, the minimum value is set to blue, and the intermediate value of the intensity is displayed in a contour line with an intermediate color between red and blue. In this case, if the whole is displayed in the same color, the dispersion of the single carbon nanotubes is uniform, and if the colors are partially different, it can be seen that the dispersion is uneven. In particular, when evaluating a defect of a device such as a thin film, the above display is very useful because it can be confirmed at a glance.

  The above-described embodiment is merely an example of the present invention, and it is apparent that changes, modifications, and additions can be made as appropriate within the scope of the present invention.

The schematic block diagram of the principal part of the photo-luminescence measuring apparatus by one Example of this invention. The detailed optical path block diagram of the photometry system containing an excitation side spectroscope and a fluorescence side spectroscope. The schematic perspective view of a sample stage. The top view which shows the whole measurement range of a sample. The flowchart which shows the procedure of the measurement of the photoluminescence of the whole sample. A three-dimensional graph (a) with dimensions of excitation wavelength, PL wavelength, and PL intensity, and a two-dimensional graph (b) with dimensions of PL wavelength and PL intensity at a specific excitation wavelength. The figure which shows an example of the three-dimensional graph of the excitation wavelength, PL wavelength, and PL intensity based on a measurement result. The figure which shows an example of the mapping image which shows intensity distribution in a certain chiral index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source part 11 ... Excitation side spectroscope 12 ... Sample stage 121 ... Movable part 122 ... Fixed part 123 ... Plate spring 13 ... Sample 14 ... Fluorescence side spectroscope 15 ... Detector 16 ... Stage X-axis drive part 17 ... Stage Y Axis drive unit 20 ... A / D converter 21 ... data processing unit 22 ... 5-dimensional data collection unit 23 ... chiral index conversion unit 24 ... mapping image creation unit 25 ... control unit 26 ... operation unit 27 ... display unit 28 ... personal computer (PC)
30 ... Lens 31, 35, 37, 45 ... Slit 32, 38, 41, 44, 46, 48 ... Mirror 33, 36, 47 ... Diffraction grating 34, 39, 40, 43 ... Toroidal mirror 49 ... Cylindrical lens

Claims (2)

In a photoluminescence measuring apparatus comprising: an irradiating unit that irradiates a sample with excitation light of a predetermined wavelength; and a detecting unit that detects the intensity of photoluminescence emitted from the sample in response to the irradiation of the excitation light.
a) sample moving means for moving the sample two-dimensionally so that the irradiation position of the excitation light on the sample can be changed;
b) Based on the photoluminescence intensity detected by the detecting means each time the excitation light irradiation position on the sample is changed by the sample moving means, the uniformity of the two-dimensional presence / absence of the contained substance in the sample / Processing means for creating information reflecting non-uniformity;
A photoluminescence measuring device comprising:   A sample containing carbon nanotubes is a measurement target, and the processing means collects data including a set of measurement position information, excitation wavelength, photoluminescence wavelength, and photoluminescence intensity on the sample by scanning the wavelength of excitation light. The combination of the excitation wavelength and the photoluminescence wavelength is converted into a chiral index characterizing the carbon nanotube, and image information indicating the distribution of the photoluminescence intensity on the sample is created for each chiral index. The photoluminescence measuring device according to 1.