A micro-measurement device for the chiral-related electrical and thermal intrinsic properties of carbon nanotubes

Abstract

The present invention relates to the field of fine measurement of nanomaterials, and in particular, to a micro-measurement device for electrical and thermal intrinsic properties of carbon nanotubes related to chirality. The device is mainly composed of a silicon substrate, a dielectric layer, a metal electrode, etc. The silicon substrate has a certain thickness and has more than two slits and through-hole marks in the central area. The dielectric layer is a silicon nitride layer, which covers the surface of the silicon substrate; the metal electrode is located on the dielectric layer, and more than two metal electrodes are provided. By adopting the device of the present invention, it is possible to quickly locate the carbon nanotube suspended on the slit under a transmission electron microscope, and accurately characterize the chiral structure of the carbon nanotube. With the help of the metal electrodes and slits on the device, the electrical and thermal properties of the same carbon nanotube with a determined chirality can be accurately measured using instruments such as Raman spectroscopy and source meters, thereby establishing the correlation between the chirality of the carbon nanotube and its electrical, thermal and other properties.

Description

Technical Field

[0001] The present invention relates to the field of nano material fine measurement, in particular to a micro-measurement device for chiral-related electrical and thermal intrinsic properties of carbon nanotubes. Background Art

[0002] Carbon nanotubes have excellent electrical and thermal properties, and therefore have attracted widespread attention. They have broad application prospects in nanoelectronic devices and thermal management. Theoretical studies have shown that the intrinsic physical properties of carbon nanotubes are closely related to their chiral structure. Exploring the direct relationship between the chiral structure of carbon nanotubes and their electrical and thermal properties is of great significance for both basic scientific research and application exploration.

[0003] The chiral structure of single-walled carbon nanotubes can be uniquely determined by a pair of indices (n, m). The chirality of carbon nanotubes can be characterized by electron diffraction, Raman spectroscopy, fluorescence spectroscopy, etc., among which electron diffraction is considered to be the most accurate means of characterizing the chirality of carbon nanotubes. Electron diffraction characterization must be carried out under a transmission electron microscope, and commercial transmission electron microscope micro-grids cannot measure the properties of the characterized samples. Researchers have developed a sample stage system (CN101275895A) for in-situ measurement of nanoelectronic device properties in a transmission electron microscope, but this system can only measure the electrical properties of the sample and cannot measure the thermal properties of carbon nanotubes. For the measurement of the intrinsic thermal properties of carbon nanotubes, the use of current self-heating combined with Raman characteristic peak shift is an effective method (Reference 1Li, Q.; Liu, C.; Wang, X.; Fan, S. Measuring the Thermal Conductivity of Individual Carbon Nanotubes by the Raman Shift Method. Nanotechnology 2009, 20 (14), 2–7.). However, the device substrate used in the literature is large in size and cannot pass through the electron beam. Therefore, it cannot be directly used to characterize the chirality of carbon nanotubes under a transmission electron microscope, and it is difficult to measure the intrinsic thermal properties related to the chirality of carbon nanotubes. In addition, there is currently a lack of measurement devices that can simultaneously correlate the chirality of carbon nanotubes with multiple physical properties (such as electrical and thermal properties). The above limitations have greatly restricted the measurement of electrical and thermal properties related to the chirality of carbon nanotubes, and there is currently no good solution. Summary of the invention

[0004] In view of the above background and technical status, the purpose of the present invention is to provide a micro-measurement device for the electrical and thermal intrinsic properties of carbon nanotubes related to chirality. The present invention can directly perform fine chiral structure characterization on a single carbon nanotube on the device, and then accurately measure the electrical and thermal intrinsic properties of the same carbon nanotube, thereby realizing the correlation between the chirality of the carbon nanotube and its electrical and thermal properties.

[0005] The technical solution of the present invention is:

[0006] A micro-measurement device for the chirality-related electrical and thermal intrinsic properties of carbon nanotubes, comprising: a silicon substrate, a dielectric layer and a metal electrode, wherein the dielectric layer is a silicon nitride layer covering the surface of the silicon substrate; more than two slits and through-hole marks are provided in the central area of ​​the silicon substrate, and the metal electrode is located on the dielectric layer on the upper surface of the silicon substrate, and more than two metal electrodes are provided.

[0007] The micro-measurement device for the chirality-related electrical and thermal intrinsic properties of carbon nanotubes has a silicon substrate thickness of 100 to 200 μm, a square, polygonal or circular shape, and a maximum diagonal length of no more than 3 mm, so that it can be placed in a transmission electron microscope sample rod to characterize the chirality of the carbon nanotubes.

[0008] In the micro-measurement device for the chiral-related electrical and thermal intrinsic properties of carbon nanotubes, the slits include a wide slit and more than two narrow slits, and the wide slit is parallel to the narrow slits.

[0009] The micro-measurement device for the chiral-related electrical and thermal intrinsic properties of carbon nanotubes has a wide slit width of 10-100 μm, a narrow slit width of 2-5 μm, and two or more protrusions evenly arranged in the middle of the narrow slit; the wide slit and the narrow slit have the same length, which is 100-500 μm.

[0010] In the micro-measurement device for measuring the electrical and thermal intrinsic properties of carbon nanotube chirality, metal electrodes are distributed on both sides of the wide slit, and the number of the metal electrodes is at least four.

[0011] In the micro-measurement device for the chiral-related electrical and thermal intrinsic properties of carbon nanotubes, the through-hole marks are a series of numerical or alphabetical through-holes arranged at equal intervals, and the through-hole marks are arranged near the narrow slits.

[0012] The design idea of ​​the present invention is:

[0013] The present invention designs slits, through-hole marks and metal electrodes on the same silicon substrate with a dielectric layer, and the size of the silicon substrate is compatible with a common transmission electron microscope sample rod. A single carbon nanotube can be directly grown on the surface of the device by chemical vapor deposition, and the carbon nanotube spans the slit and is connected to the metal electrode. The narrow slit and the through-hole mark nearby can achieve efficient and accurate characterization of the chiral structure of the carbon nanotube, and the design of a narrow slit width can reduce the vibration amplitude of the sample under electron beam irradiation. The carbon nanotube on the wide slit can be measured by the Raman peak shift method under electric heating to obtain the thermal conductivity value of the single carbon nanotube. In addition, the metal electrodes on both sides of the wide slit can measure the electrical properties of the suspended carbon nanotube.

[0014] The advantages and beneficial effects of the present invention are:

[0015] The device of the present invention can be directly used for the fine characterization of the chiral structure of carbon nanotubes. The through-hole marks on the device and the protrusions on the narrow slits can be used to quickly locate the carbon nanotubes under a transmission electron microscope, thereby improving the characterization efficiency and the accuracy of the correlation structure-property relationship. With the help of the metal electrodes and slits on the device, the electrical and thermal properties of the same carbon nanotube with a determined chirality can be measured using instruments such as Raman spectroscopy and source meters. The sample test area is a wide slit, and the chiral characterization area is a narrow slit, which can avoid the influence of electron beam irradiation on the structure and performance of the carbon nanotubes during characterization. Thereby, the chirality of the carbon nanotubes is associated with intrinsic properties such as electrical and thermal properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 .Schematic diagram of the front structure of the device of the present invention; in the figure, 1 is a metal electrode, 2 is a wide slit, 3 is a narrow slit, 4 is a through-hole mark, 5 is a silicon substrate, and 6 is a dielectric layer.

[0017] Figure 2 . Figure 1 A local enlarged view of the central area; in the figure, 1 is a metal electrode, 2 is a wide slit, 3 is a narrow slit, 4 is a through-hole mark, 5 is a silicon substrate, 6 is a dielectric layer, and 7 is a protrusion.

[0018] Figure 3 .Structural characterization data of a single-walled carbon nanotube; where (a) is a scanning electron microscope (SEM) photo at low magnification, (b) is a SEM photo at a wide slit position at high magnification, (c) is a transmission electron microscope photo of the carbon nanotube, and (d) is an electron diffraction pattern of the single-walled carbon nanotube.

[0019] Figure 4. The electrical properties and Raman spectrum test results of carbon nanotubes; (a) is the electrical properties test result diagram, the horizontal axis V represents the voltage (v), and the vertical axis I represents the current (A); (b) is the Raman spectrum test result diagram, the horizontal axis Raman shift represents the Raman shift (cm -1 ), the vertical axis Raman intensity represents the intensity (au).

[0020] Figure 5 A set of typical test data of thermal properties of carbon nanotubes; (a) is the relationship between temperature and Raman peak position, the horizontal axis Temperature represents temperature (K), and the vertical axis G band frequency represents the Raman peak position of G peak (cm -1 ); (b) is the relationship between heating power and Raman peak position, the horizontal axis Heating power represents the current heating power (nW), and the vertical axis Gband frequency represents the Raman peak position of G peak (cm -1 ). DETAILED DESCRIPTION

[0021] In order to further understand the content of the present invention, the present invention is described in detail below with reference to the accompanying drawings and examples.

[0022] See also Figure 1 , Figure 2 This embodiment provides a micro-measurement device for measuring the chiral-related electrical and thermal intrinsic properties of carbon nanotubes, including a silicon substrate 5, a dielectric layer 6 and a metal electrode 1, and the specific structure is as follows:

[0023] The silicon substrate 5 is a square thin sheet with a thickness of 200 μm and a side length of 2.1 mm. The surface of the silicon substrate 5 is covered with a silicon nitride dielectric layer 6, and the thickness of the silicon nitride dielectric layer 6 is 100 nm. The size of the silicon substrate 5 is compatible with the sample rod of a common transmission electron microscope. The silicon substrate 5 and the dielectric layer 6 are partially etched by deep silicon etching and wet etching processes, so that more than two slits and through-hole marks 4 are formed in the central area of ​​the silicon substrate 5, and the slits include a wide slit 2 and more than two narrow slits 3.

[0024] Among them, the wide slit 2 is rectangular, with a width of 30μm and a length of 300μm. It is mainly used for measuring the properties of the sample. The wider slit is conducive to generating a sufficiently large temperature gradient, which is convenient for measuring the thermal properties of carbon nanotubes. The narrow slit 3 has a width of 4μm and a length of 300μm. Two or more protrusions 7 are evenly arranged in the middle to form a wave shape. It is mainly used for positioning carbon nanotubes under a transmission electron microscope and fine characterization of the chiral structure. The narrower slit width can reduce the vibration amplitude of the sample under electron beam irradiation. Separating the sample test area from the characterization area can avoid the influence of electron beam irradiation on the sample structure and performance during characterization. There are a series of equally spaced digital through-hole marks 4 near the narrow slit 3, which is convenient for rapid positioning of carbon nanotubes under a transmission electron microscope. A metal electrode 1 is set on the dielectric layer 6 on the front of the silicon substrate 5, and the number of metal electrodes 1 is five. The metal electrodes 1 are distributed on both sides of the wide slit 2, and can electrically connect and test the suspended carbon nanotubes on the wide slit 2. The use of a four-wire method for testing can greatly reduce the impact of contact resistance.

[0025] like Figure 3 The data shown are the data of the structural characterization of a single-walled carbon nanotube. Figure a is a scanning electron microscope (SEM) photo taken at low magnification. It can be seen that there is a carbon nanotube in the upper part of the figure that crosses all electrodes and wide and narrow slits. It is generally believed that the same carbon nanotube maintains uniform structure at different positions. Figure b is a SEM photo of the wide slit position at high magnification. The suspended carbon nanotube can be seen, indicating that the carbon nanotube can be stably placed on both ends of the slit. The device is placed in a transmission electron microscope for chiral structural characterization. The position of the carbon nanotube on the narrow slit can be easily located through the through-hole mark 4, and a transmission electron microscope photo of the carbon nanotube is obtained (Figure c). Through the transmission electron microscope photo, the number of walls and diameter of the carbon nanotube can be clearly distinguished. Figure d is the electron diffraction pattern of this single-walled carbon nanotube. Using the information of the upper line of the diffraction pattern, it can be obtained that the chiral index of the carbon nanotube is (16, 34) and its diameter is 3.46nm.

[0026] After the chiral structure characterization of the carbon nanotubes is completed, they are taken out for measurement of electrical and thermal properties. Figure 4 The following are the experimental results of measuring the electrical properties and Raman spectrum of carbon nanotubes. Figure a is the IV curve of a single carbon nanotube sample measured by a semiconductor analysis tester. The curve has good linearity, indicating that a good ohmic contact is formed between the carbon nanotube and the electrode. The resistance of the sample is about 126 kΩ. Figure b is the Raman spectrum of the single-walled carbon nanotube. It can be seen that at 1580 cm -1 There is an obvious peak near it, and no obvious defect peak (~1350cm -1 ), indicating that the carbon nanotube sample has good crystallinity.

[0027] like Figure 5 The figure shows a set of typical data for measuring the thermal properties of carbon nanotubes. Figure a shows the Raman peak position of carbon nanotubes at different temperatures. The temperature increase of carbon nanotubes under electric heating can be obtained through the change of peak position in the Raman spectrum. Figure b shows the change of Raman peak position of the center point of the suspended carbon nanotube with the electric heating power. The suspended carbon nanotubes are heated by electric current. Under different heating powers, the Raman peak position of the sample will produce different degrees of deviation. After obtaining the Raman peak-temperature coefficient, Raman peak-heating power coefficient, and structural information of the carbon nanotubes, the thermal conductivity of the carbon nanotubes is calculated to be 2625.9Wm through the Fourier heat transfer formula. -1 K -1 .

[0028] The results of the embodiment show that the device of the present invention can realize the rapid positioning of the carbon nanotube suspended on the slit under the transmission electron microscope, and accurately characterize the chiral structure of the carbon nanotube. With the help of the metal electrodes and slits on the device, the electrical and thermal properties of the same carbon nanotube with a determined chirality can be accurately measured by using instruments such as Raman spectroscopy and source meter, so as to establish the correlation between the chirality of the carbon nanotube and its electrical, thermal and other properties.

[0029] The above embodiments of the present invention are only used as examples for reference and are not intended to limit the scope of the present invention. We may modify and change the above embodiments, but these shall not deviate from the spirit of the present invention and the scope of the appended claims.

Claims

1. A micro-measurement device for measuring the chiral-related electrical and thermal intrinsic properties of carbon nanotubes, characterized in that: The device comprises: a silicon substrate, a dielectric layer and a metal electrode, wherein the dielectric layer is a silicon nitride layer covering the surface of the silicon substrate; the central area of ​​the silicon substrate is provided with more than two slits and through hole marks, and the metal electrode is located on the dielectric layer on the upper surface of the silicon substrate, and more than two metal electrodes are provided; The slits include a wide slit and two or more narrow slits, the wide slit is parallel to the narrow slits; the width of the wide slit is 10 to 100 μm, the width of the narrow slit is 2 to 5 μm, and two or more protrusions are evenly arranged in the middle of the narrow slits; the length of the wide slit is the same as that of the narrow slit, which is 100 to 500 μm.

2. The micro-measurement device for measuring the chiral-related electrical and thermal intrinsic properties of carbon nanotubes according to claim 1, characterized in that: The thickness of the silicon substrate is 100-200 μm, and the shape of the silicon substrate is square, polygonal or circular. The maximum diagonal length of the silicon substrate does not exceed 3 mm, so that it can be placed in a transmission electron microscope sample rod to characterize the chirality of the carbon nanotubes.

3. The micro-measurement device for measuring the chiral-related electrical and thermal intrinsic properties of carbon nanotubes according to claim 1, characterized in that: The metal electrodes are distributed on both sides of the wide slit, and the number of the metal electrodes is at least four.

4. The micro-measurement device for measuring the chiral-related electrical and thermal intrinsic properties of carbon nanotubes according to claim 1, characterized in that: The through hole markings are a series of through holes with numbers or letters arranged at equal intervals, and the through hole markings are located near the narrow slits.

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