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Rapid optical characterization method for horizontal array density of carbon nanotubes on substrate

A carbon nanotube and horizontal technology, applied in the field of fast optical characterization, can solve the problems of weak optical signal, small optical cross-section, difficult clear acquisition, etc., and achieve the effect of improving the signal level

Inactive Publication Date: 2015-06-10
PEKING UNIV
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  • Application Information

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Problems solved by technology

However, the optical characterization method of carbon nanotube density is still technically a huge challenge
The basic difficulty lies in: due to the complexity of the structure and optical properties of carbon nanotubes, there is no way to directly link the density and optical contrast of carbon nanotubes in theory; at the same time, the diameter of a single carbon nanotube is on the order of 1 nm, and its optical The active cross section is very small, the optical signal is very weak and it is difficult to collect clearly

Method used

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  • Rapid optical characterization method for horizontal array density of carbon nanotubes on substrate
  • Rapid optical characterization method for horizontal array density of carbon nanotubes on substrate
  • Rapid optical characterization method for horizontal array density of carbon nanotubes on substrate

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Effect test

Embodiment 1

[0026] Embodiment 1, optical characterization of carbon nanotube horizontal array density

[0027] The Thomas-Reiche-Kuhn summation rule states that for any particle with the same number of electrons, the sum of the oscillator strengths between its various energy levels is equal. Integrating the absorption spectra of different types of carbon nanotubes, the integral values ​​are basically distributed on the same straight line, which is equivalent to the absorption of graphene. Theoretical analysis of the contrast of graphene and carbon nanotube horizontal arrays indicates that the contrast is proportional to the absorption coefficient. That is, we can derive the absorption coefficient of the sample from the optical contrast of the sample, thereby obtaining the density of the horizontal array of carbon nanotubes. Specific principles such as figure 1 shown.

[0028] The invention takes optical photos of carbon nanotube samples under different polarization angles, and uses mat...

Embodiment 2

[0036] Embodiment 2, optical contrast characterization of carbon nanotube type

[0037] Carbon nanotubes can be seen as coiled graphene. Different coiling directions and tube diameters make carbon nanotubes have different chiral indices (n, m), where n and m are both integers. When the polarization direction of the incident light is parallel to the tube axis, the selection rule requires that electrons can only transition between energy levels with the same symmetry. E. ii (i=1, 2, 3...N, where N is a positive integer) marks the transition energy of electrons at different energy levels with the same symmetry, such as E 11 is the transition between the lowest energy levels of carbon nanotubes, E 22 is the transition before the second energy level. for the same E ii , the transition energy of carbon nanotubes with different chirality is different. If (3n+m) is divisible by 3, then the dividing line of the carbon nanotube passes through the K point, and the carbon nanotube i...

Embodiment 3

[0038] Embodiment 3, using the cross polarization method to improve the optical signal level of the carbon nanotube horizontal array

[0039] The signal level of light scattered by carbon nanotubes is usually very weak (the contrast is on the order of 0.1%), much smaller than the signal level of background light or even noise, which brings great difficulties to the optical characterization of carbon nanotubes. The invention remarkably improves the optical signal level of the carbon nanotube through the method of cross polarization, and remarkably weakens the possible error caused by the optical absorption of interference factors such as dirty spots and catalysts on the sample to the experiment.

[0040] A pair of near-vertical polarizers (deviation from perfect vertical: δ radians) are placed on both sides of the sample, and the carbon nanotube growth direction of the carbon nanotube horizontal array is at an angle of 45° to the first polarizer. The incident light passes throu...

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Abstract

The invention discloses a rapid optical characterization method for the horizontal array density of carbon nanotubes on a substrate. The method comprises the following steps: generalizing the optical absorption properties of a single carbon nanotube into a macroscopic material, introducing an optical characterization method of a two-dimensional material (such as graphene) into the horizontal array field of the carbon nanotubes, establishing a quantitative formula among the optical contrast, the horizontal array density of the carbon nanotubes, and the ratio of different types of the carbon nanotubes, and obviously increasing an optical signal (10-100 times) of the carbon nanotubes by using a cross polarization method, so that the optical characterization of horizontal arrays of the high-density carbon nanotubes is realized. The method provided by the invention can be used for overcoming the defects that traditional characterization methods have time-consuming effect and are complex to operate, and samples are easily damaged, and can be used for achieving the rapid, accurate, noninvasive characterization of the density and type of the carbon nanotubes on the substrate, and therefore, the method can be applied to the growth and test experiments of the carbon nanotubes, and provide essential monitoring and feedback measures for the optimization of carbon nanotube growth methods.

Description

technical field [0001] The invention relates to a fast optical characterization method for the horizontal array density of carbon nanotubes on a substrate. Background technique [0002] The heart of modern information technology is integrated circuit chips, and 90% of these chips are derived from silicon-based complementary metal oxide semiconductor (CMOS) technology. It is predicted that silicon-based CMOS technology will reach its physical limit around 2020. Among the few candidate materials, carbon nanotube materials are the only materials that can continue to improve the overall performance of the system by reducing the device size until the 5nm node, and are the most promising alternative materials for silicon materials. In 2012, scientists at IBM Washington Research Center have used carbon nanotubes instead of semiconductor silicon to realize the construction of 9nm carbon nanotube-based field effect transistors. In the same year, they precisely placed more than 10,0...

Claims

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Application Information

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IPC IPC(8): G01N21/31
Inventor 刘开辉唐静怡邓时滨康黎星胡悦张锦
Owner PEKING UNIV
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