JP2006242591A - Method and device for measuring outer diameter and refractive index of nano fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for accurately measuring the outer diameter of a nano carbon tube having an outer diameter of several nm to several tens nm and a narrower nano fiber having an outer diameter of 200 nm or smaller. <P>SOLUTION: A deviation index expressed by a function of the outer diameter and the refractive index of the nano fiber is calculated based on the measured scattered light intensity of scattered light of a predetermined scattering angle obtained by projecting perpendicularly polarized light polarized perpendicularly to the length direction of the nano fiber to the nano fiber and the calculated scattered light intensity calculated from the scattering angle. A combination of the outer diameter and refractive index of the nano fiber having a minimum deviation index is determined. Thus, the outer diameter and refractive index of the nano fiber is determined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to both the outer diameter and the refractive index of an extremely thin nanofibrous object such as a nanocarbon tube, an ultrafine fiber knitted fabric, and a metallic superconducting wire knitted fabric, particularly a thin cylindrical body having an outer diameter of 200 nm or less The present invention relates to a method for measuring simultaneously and a measuring apparatus therefor.

It is known that these outer diameters have a great influence on the production of nanocarbon tubes, ultrafine fibers, metallic superconducting wires, etc., or their characteristics. Accordingly, methods for measuring the outer diameter have been developed.
Patent Document 1 shows that a fiber having an outer diameter of about 10 μm can be measured by measuring the outer diameter at the time of fiber production based on a method of obtaining the ratio of the diffraction intensity of laser light.
Patent Documents 2 and 3 disclose that a thin line having an outer diameter of 17.5 μm can be measured by a method of calculating the outer diameter from the diffraction pattern of the Fraunhofer diffraction image of the thin line to be measured by laser light. Yes.

However, there was no effective measurement method for measuring the outer diameter of nanofibers in the order of nm.
Therefore, as shown in Non-Patent Document 1, the present inventors use a laser beam obtained by polarizing a laser beam vertically or horizontally with respect to the object to be measured, and measure the scattering intensity by the object to be measured. We developed a method to measure the outer diameter and refractive index from the deviation from the calculated value based on the base. According to this method, it was shown that a thin cylindrical body having an outer diameter of about 240 nm can be measured.

JP-A-5-45130 JP-A-6-288723 JP-A-6-241733 Fumiaki Tajima, Yoshiro Nishiyama, “Examination of the possibility of measuring the thickness and refractive index of a spider thread with a thickness of about 120 nm”, Proceedings of the 64th Annual Meeting of the Japan Society of Applied Physics, Japan Society of Applied Physics, March 2004

In the outer diameter measuring method by the present inventors, it was possible to measure the outer diameter of a columnar body having a smaller diameter as compared with the measuring method shown in Patent Documents 1 to 3 of 240 nm and earlier. It was difficult to accurately measure the outer diameter of thinner nanofibers of several nanometers to 200 nm, such as carbon tubes.
Therefore, the present invention provides a method and a measuring apparatus for accurately measuring the outer diameter of a nanocarbon tube having an outer diameter of several nanometers to several tens of nanometers or a thinner nanofiber having an outer diameter of 200 nm or less.

  According to the first aspect of the present invention, the measured scattered light intensity by the scattered light having a predetermined scattering angle obtained by projecting the vertically polarized light, which is deflected perpendicularly to the length direction of the nanofiber, onto the nanofiber, and the scattering From the calculated scattered light intensity calculated from the angle, a deviation index represented by a function of the outer diameter and refractive index of the nanofiber is calculated, and the combination of the outer diameter and refractive index of the nanofiber that minimizes the deviation index By determining the outer diameter and refractive index of the nanofiber, the outer diameter and refractive index of the nanofiber are measured.

  According to the second aspect of the present invention, the measured scattered light intensity by the scattered light having a predetermined scattering angle obtained by projecting parallel polarized light deflected parallel to the length direction of the nanofiber onto the nanofiber, and the scattering From the calculated scattered light intensity calculated from the angle, a deviation index represented by a function of the outer diameter and refractive index of the nanofiber is calculated, and the combination of the outer diameter and refractive index of the nanofiber that minimizes the deviation index By determining the outer diameter and refractive index of the nanofiber, the outer diameter and refractive index of the nanofiber are measured.

  The invention according to claim 3 is characterized in that the outer diameter of the nanofiber for measuring the outer diameter and the refractive index is 200 nm or less, and the outer diameter and refractive index of the nanofiber according to claim 1 or 2 This is a measurement method.

  According to a fourth aspect of the present invention, there is provided a light source unit that emits laser light, a light deflecting unit that converts the laser light into vertical polarization or horizontal horizontal polarization perpendicular to the length direction of the object to be measured, and light of the laser light. On the shaft, there is a support base for supporting and fixing the object to be measured provided in a fixed state, and a detector for detecting the scattered light intensity of the laser light scattered by the object to be measured and outputting it to the outside. A detection unit that rotates to a predetermined scattering angle and outputs the scattering angle to the outside, and calculates the scattered light intensity and deviation index from the scattering angle and scattered light intensity output from the detection unit, and the object to be measured It is the measuring part comprised by the calculating part which calculates the outer diameter and refractive index of nanofiber, It is the measuring apparatus of the outer diameter and refractive index of nanofiber characterized by the above-mentioned.

  According to a fifth aspect of the present invention, there is provided a light source unit that emits laser light, a light deflecting unit that converts the laser light into vertical polarization or horizontal horizontal polarization perpendicular to the length direction of the object to be measured, and light of the laser light. A support base for supporting and fixing the measurement object provided in a fixed state on the axis, and a detector for detecting the scattered light intensity of the laser light scattered by the measurement object and outputting it to the outside are circled around the support base. On the circumference, at least two detection units provided at a predetermined angle as the scattering angle, and the calculated scattered light intensity and deviation index are calculated from the scattering angle and scattered light intensity output from the detection unit, and the measured object An apparatus for measuring an outer diameter and a refractive index of a nanofiber, characterized in that it is configured with a calculation unit that calculates an outer diameter and a refractive index.

  According to the present invention, it is possible to efficiently and accurately measure the outer diameter of a nanofiber having an outer diameter of 200 nm or less and its refractive index, and this has a remarkable industrial effect.

The outer diameter and refractive index measurement method according to the present invention proceeds as shown in the flowchart of FIG.
First, the outer diameter / refractive index measuring apparatus 1 shown in FIG. 2 emits laser light 3a having a wavelength of λ nm (543.5 nm) from the light source 3 to the object to be measured 2, and the laser light 3a is deflected by the deflecting device 4. Thus, the polarized light or the horizontally polarized light is applied to the object to be measured and is projected onto the object to be measured 2 supported on the upper surface of the detection unit 5 by the support base 5b. A part of the laser beam 3a is reflected by the object to be measured 2, and the measured scattered light intensity I is measured by the detector 6 disposed at the scattering angle θ with respect to the optical axis of the laser beam 3a. In this procedure, the scattering angle θ _i (i = 0... N) is changed, and the measured scattered light intensity I _i (i = 0... N) at that time is sequentially measured.
Alternatively, as shown in FIG. 3, a plurality of detectors 6 (28 in the case of FIG. 3) are arranged on the circumference of the support 5 b that supports the DUT 2, and the scattering angle θ of each detector 6. _i in may be to measure the measuring scattered light intensity i _i.

These detection angles θ _i and measured scattered light intensity I _i are sent to a calculation unit 7 such as a personal computer equipped with the simultaneous outer diameter / refractive index analysis program shown in FIG.
The calculated scattered light intensity σ _i is calculated in the calculation unit 7.
In the present invention, as a result of various studies as a formula for calculating the calculated scattered light intensity, by using the first type and the third type Bessel function, the accuracy of the calculation of the outer diameter and the refractive index can be improved. It has been found that a good value can be obtained.
When calculating the calculated scattered light intensity σ _i , calculation is performed using Equation 1 when scattered by vertically polarized light, and calculation is performed using Equation 2 when scattered horizontally polarized light.

ここで、添字‖は水平偏光によるものを表し、ｋは波数、ｒ_０は被測定物の半径（Ｄ_０／２）、Ｊ_ｍ（ｘ）は第一種ベッセル関数、Ｈ_ｍ ^（１）（＝Ｊ_ｍ（ｘ）+ｉＹ_ｍ（ｘ））は第三種ベッセル関数を表し、ｍは次数である。

Here, the subscript 表 し represents horizontal polarization, k is the wave number, r ₀ is the radius of the object to be measured (D _0/2 ), J _m (x) is the first-type Bessel function, and H _m ⁽¹⁾ ( = J _m (x) + iY _m (x)) represents a Bessel function of the third kind, and m is an order.

ここで、添字⊥は垂直偏光によるものを表し、Ｊ_ｍ ^‘（ｘ）は第一種ベッセル関数を表し、Ｈ_ｍ ^’（１）（＝Ｊ_ｍ（ｘ）+ｉＹ_ｍ（ｘ））は第三種ベッセル関数を表し、ｍは次数である。

Here, the subscript ⊥ represents vertical polarization, J _m ^′ (x) represents a first-class Bessel function, and H _m ^{′ (1)} (= J _m (x) + iY _m (x)) Represents a triple Bessel function, where m is the order.

  By the way, the calculated scattered light intensity formulas shown in Equations 1 and 2 are effective for measuring the outer diameter and refractive index of highly transparent materials such as fiber knitted fabrics and yarns. In the case of a highly reflective metal such as a conductive wire or a hollow sample such as a carbon nanotube, the calculated scattered light intensity formula can be changed to a more suitable formula, so that the outer diameter and the refractive index of the present invention can be adjusted simultaneously. Measurements can be made.

Next, using the measured scattered light intensity calculation σ _i calculated from the measured measured scattered light intensity I _i and the detected angle θ _i , the deviation index U (including the outer diameter D and the refractive index n shown in Equation 3 is used. n, D). Using this deviation index as a function of the outer diameter D and the refractive index n, a point (n ₀ , D ₀ ) at which the deviation index is minimum is obtained, and the combination of the outer diameter D and the refractive index n in that case is determined from the outside of the object to be measured. Diameter and refractive index.

First, this calculation shows an optimal distribution when I _i ^(opt) = bσ _i (n ₀ , D ₀ ) when the deviation index is the outer diameter D ₀ and the refractive index n ₀ , and the optimal deviation in this optimal distribution The index U _T ^(opt) (n, D) is expressed as in Equation 3.

ここで、Ｎは測定数、ｂは入射波強度を表す。

Here, N represents the number of measurements, and b represents the incident wave intensity.

Then, a set G of deviation indices as a function of the outer diameter D and the refractive index n is set as G = {n, D | U _T ^(opt) (n, D) ≦ U _T (n ₀ , D ₀ )}. Within that range, n _min , n _max , D _min , and D _max are determined from _Equation 4. The difference between the obtained values and n ₀ , D ₀ , the outer diameter is (D _min −D ₀ , D ₀ −D ₀ ), and the refractive index is (n _min −n ₀ , n _max −n _0). ) Is defined as uncertain, and the point (n ₀ , D ₀ ) that minimizes this value is calculated to calculate the outer diameter and refractive index of the object to be measured.

As an example calculated in this manner, a deviation index U (n, D) of a fiber braid having an outer diameter of 500 nm.
) Are shown as a function of the outer diameter D and the refractive index n in FIGS. 4 (a) and 4 (b). FIG. 4A shows the global coordinates, and FIG. 4B shows an enlarged view of the vicinity of coordinates (n ₀ , D ₀ ) where U (n, D) indicates the minimum point. is there.

Hereinafter, the present invention will be described using examples.
First, fiber knitting elements having outer diameters of 250 nm and 200 nm, and warp yarns having outer diameters of 150 nm, 100 nm, and 90 nm were used as objects to be measured. These outer diameters are measured in advance using a scanning electron microscope (SEM).
These samples are set on the support 5b of the outer diameter / refractive index measuring apparatus 1 of FIG. 2, and a laser beam having a wavelength λ = 534.5 nm is projected, and the scattering angle θ _i is between 0 ° and 150 °. The scattering intensity was measured in order of 2 degrees, and the scattering intensity was measured to obtain the measured scattered light intensity I _i .

Next, the previous scattering angle θ _i and the measured scattered light intensity I _i are input to a personal computer, the calculated scattered light intensity σ _i is obtained from the scattered angle θ _i, and the calculated scattered light intensity I _i is obtained as the calculated scattered light intensity σ. _A deviation index U (n, D) is calculated from _i , a value that minimizes U (n, D) is obtained as an optimum value, and D and n at that time are taken as an outer diameter and a refractive index, respectively. The results are shown in Table 1 together with the actual measurement values. The measurement was performed with both vertically polarized light and horizontally polarized light.

  As is apparent from Table 1, it can be seen that the outer diameter obtained by the present invention is a value measured by a scanning electron microscope and a value within several percent even in a nanofiber having a small diameter of 90 nm.

Measuring method flowchart according to the present invention Example of outer diameter / refractive index measuring device Another example of outer diameter / refractive index measuring device Change of deviation index by outer diameter D and refractive index n of sample with outer diameter of 500 nm

Explanation of symbols

1 Outer diameter / refractive index measuring device 2 Object to be measured (nanofiber)
DESCRIPTION OF SYMBOLS 3 Light source 3a Laser beam 3b Scattered light 4 Deflector 5a Detection part 5b Support stand 6 Detector 7 Calculation part (theta) _i Scattering angle I _i Measurement light scattering intensity (sigma) _i Calculation scattered light intensity D Outer diameter n Refractive index

Claims (5)

The measured scattered light intensity by the scattered light at a predetermined scattering angle obtained by projecting the vertically polarized light, which is deflected perpendicularly to the length direction of the nanofiber, onto the nanofiber, and
From the calculated scattered light intensity calculated from the scattering angle,
By calculating a deviation index represented by a function of the outer diameter and refractive index of the nanofiber, and obtaining a combination of the outer diameter and refractive index of the nanofiber that minimizes the deviation index, the outer diameter of the nanofiber And a method of measuring the outer diameter and refractive index of the nanofiber, wherein the refractive index is obtained. Measured scattered light intensity by scattered light of a predetermined scattering angle obtained by projecting parallel polarized light deflected parallel to the length direction of the nanofiber onto the nanofiber, and
From the calculated scattered light intensity calculated from the scattering angle,
By calculating a deviation index represented by a function of the outer diameter and refractive index of the nanofiber, and obtaining a combination of the outer diameter and refractive index of the nanofiber that minimizes the deviation index, the outer diameter of the nanofiber And a method of measuring the outer diameter and refractive index of the nanofiber, wherein the refractive index is obtained. The method for measuring the outer diameter and refractive index of a nanofiber according to claim 1 or 2, wherein the outer diameter of the nanofiber for measuring the outer diameter and the refractive index is 200 nm or less. A light source that emits laser light;
An optical deflector that converts laser light into vertical polarization or horizontal horizontal polarization perpendicular to the length direction of the object to be measured;
A support base for supporting and fixing a measurement object provided in a fixed state on the optical axis of the laser beam;
A detector that detects the scattered light intensity of the laser light scattered by the object to be measured and outputs it to the outside. The detector rotates to reach a predetermined scattering angle, and the scattering angle is output to the outside. And
With the calculation unit that calculates the calculated scattered light intensity and deviation index from the scattering angle and scattered light intensity output from the sample rotation stage and the detector, and calculates the outer diameter and refractive index of the object to be measured,
An apparatus for measuring the outer diameter and refractive index of a nanofiber, characterized in that it is configured. A light source that emits laser light;
An optical deflector that converts laser light into vertical polarization or horizontal horizontal polarization perpendicular to the length direction of the object to be measured;
A support base for supporting and fixing a measurement object provided in a fixed state on the optical axis of the laser beam;
At least two detectors that detect the scattered light intensity of the laser light scattered by the object to be measured and output it to the outside are provided around the support base on the circumference at a predetermined angle as a scattering angle. When,
With a calculation unit that calculates the calculated scattered light intensity and deviation index from the scattering angle and scattered light intensity output from the detector to calculate the outer diameter and refractive index of the object to be measured,
An apparatus for measuring the outer diameter and refractive index of a nanofiber, characterized in that it is configured.

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