CN101293629A - Preparation method of carbon nanotube or nanowire bifurcation structure - Google Patents

Abstract

The invention discloses a method for preparing a bifurcation structure of carbon nanotubes or nanowires. The method comprises: preparing a chip, the chip including a pair of parallel electrodes and several floating-point electrodes between the parallel electrodes; /or nanowires are dissolved in an organic solvent and ultrasonically dispersed to obtain a suspension of carbon nanotubes and/or nanowires; the chip is immersed in the suspension, and alternating current or direct current is applied to the above electrodes; the chip is taken out , blow-dried to obtain a bifurcated structure of two or more carbon nanotubes and/or nanowires between the floating electrodes. The present invention utilizes an alternating electric field or an alternating induced electric field to obtain a Y or T-shaped bifurcated structure, which has good controllability, simple method, and high efficiency; meanwhile, since the obtained bifurcated structure is connected to electrodes, it can be On-chip in situ implementation of bifurcated junction devices or arrays of junction devices provides a new integration method for nanoelectronic devices.

Description

Preparation method of carbon nanotube or nanowire bifurcation structure

technical field

The invention relates to a processing method of carbon nanotubes, in particular to a preparation method of carbon nanotubes or nanowire bifurcated structures.

Background technique

Carbon nanotubes and semiconducting nanowires can be used as new nanomaterials for nanoelectronic devices. In recent years, various novel nanoelectronic devices based on carbon nanotubes or semiconductor nanowires have been successfully developed, the most prominent of which are junction devices (molecular junctions or nanowire heterogeneous devices). In order to make carbon nanotubes or semiconductor nanowires into nano-scale junction devices, carbon nanotubes or semiconductor nanowires with Y-shaped or T-shaped bifurcated structures can be used, and carbon nanotubes on each branch in the Y-shaped or T-shaped bifurcated structure can be used. The different electrical properties of nanotubes or nanowires can build junction devices with rectifying properties, and it has even been reported that a single Y-shaped bifurcated carbon nanotube can be used to construct a logic gate, due to the small size of this type of device and the advantages of integration , has attracted the attention of researchers.

At present, the Y-shaped bifurcated structure of carbon nanotubes and nanowires is mainly obtained by direct chemical synthesis. There are three main methods: (1) Y-shaped carbon nanotubes or semiconductor nanowires are prepared by chemical vapor deposition (CVD) (B.C.Satishkumar et al. ., Applied Physics Letters 77, 2530 (2000)); (2) Using a porous alumina template, the alumina channel is prefabricated into a Y shape, and then the nanowires are obtained by electrochemical deposition, and the Y shape can be obtained by removing the alumina Nanowires (Y.Tan et al., Appl.Phys.Lett., 85, 967 (2004)); (3) Combining alumina template and chemical vapor deposition to prepare Y-shaped carbon nanotubes (CPpadopoulos et al., Phys . Rev. Lett. 85, 3476 (2000); Guowen Meng et al., PNAS 102, 7074 (2005)). The chemical vapor deposition method is used to prepare Y-shaped structures, the process is random and poorly controllable; the use of alumina templates and electrochemical deposition is mainly used for the preparation of metal nanowires due to the need for oxidation-reduction reactions. Semiconductor nanowires are difficult; the combination of alumina templates and chemical vapor deposition, although controllable, is mainly multi-walled carbon nanotubes with many structural defects.

Contents of the invention

The invention overcomes the deficiencies in the prior art, utilizes the polarization phenomenon and the electrophoretic force effect of carbon nanotubes or semiconductor nanowires in an alternating electric field, and provides a method for preparing a bifurcated structure of carbon nanotubes or nanowires .

Technical scheme of the present invention is:

A method for preparing a carbon nanotube or nanowire bifurcated structure, the steps comprising:

1) Prepare a chip, which includes a pair of parallel electrodes and several floating electrodes between the parallel electrodes;

2) Dissolving carbon nanotubes and/or nanowires in an organic solvent and ultrasonically dispersing them to prepare a suspension of carbon nanotubes and/or nanowires;

3) immersing the chip in the suspension, and applying alternating current or direct current to the above-mentioned electrodes;

4) Take out the chip, dry it, and obtain a bifurcated structure of two or more carbon nanotubes and/or nanowires between the floating electrodes.

In the step 1), metal electrodes are prepared by photolithography and lift-off technology in the microelectronic processing technology, and the relative distance between the parallel electrodes is 1-10 μm. In the step 1), the distance between the adjacent electrodes of the floating point electrodes is 200 μm. -500nm.

The organic solvent is ethanol, acetone, n-hexane, isopropanol, dimethylformamide, 1,2-dichloroethane.

The semiconductor nanowires are: simple element nanowires or compound semiconductor nanowires.

The carbon nanotubes are: single-walled carbon nanotubes, multi-walled carbon nanotubes or tube bundles formed by aggregation of single-walled carbon nanotubes.

In the step 3), an alternating current is applied to the electrodes, and the specific parameter range of the applied alternating current is V _PP =0.5-25V, and the frequency is 1-10MHZ.

Compared with prior art, the beneficial effect of the present invention is:

The invention obtains a Y or T-shaped bifurcated structure by designing an electric field with a specific structure and using an alternating electric field or an alternating induction electric field, which has good controllability, simple method and high efficiency; not only can prepare carbon nanotubes, but also can A Y or T-shaped bifurcated structure of semiconductor nanowires, or a Y- or T-shaped bifurcated structure of carbon nanotubes and semiconductor nanowires are prepared, and a large number of bifurcated structures can be obtained according to the present invention. Especially important, since the obtained bifurcated structure is connected with electrodes, bifurcated junction devices or arrays of junction devices can be realized in situ on the same chip, providing a new integration method for nanoelectronic devices.

Description of drawings

Fig. 1 prepares the composite electrode structure schematic diagram of carbon nanotube or nanowire bifurcated structure;

Fig. 2 prepares carbon nanotube or nanowire bifurcated structure experimental device diagram;

Fig. 3 prepares the schematic diagram of carbon nanotube or nanowire bifurcated structure;

Fig. 4 Photos of scanning electrodes with bifurcated structure: (a) Y-shaped carbon nanotubes: (b) T-shaped carbon nanotubes.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

Disperse the carbon nanotubes and/or semiconductor nanowires in an organic solvent, such as ethanol, acetone, n-hexane, isopropanol, dimethylformamide, 1,2-dichloroethane or deionized water. Before the Y-shaped bifurcated structure is prepared, the solution needs to be ultrasonically dispersed for a long time to obtain a uniformly dispersed suspension of carbon nanotubes or semiconductor nanowires. The carbon nanotubes used are: single-wall carbon nanotubes, multi-wall carbon nanotubes or carbon nanotube bundles; the semiconductor nanowires are: elemental element nanowires (Si, Ge) and compound semiconductor (GaN, InP, CdS, etc.) nanowires .

In order to prepare Y-shaped carbon nanotubes and nanowire bifurcated structures, micron-scale metal electrodes are designed. The electrode is a composite structure of parallel electrodes 1 and floating-point electrodes 2, that is, several rows of cylindrical floating-point electrodes 2 are arranged between a relatively parallel electrode 1 (as shown in Figure 1), and two adjacent rows of cylindrical floating-point electrodes 2 It can be arranged at equal intervals, or a certain distance can be staggered, wherein: the distance between the parallel electrodes 1 is in the range of 10-20 μm, and the distance between the nearest neighbor floating point cylinders 2 is in the range of 2-5 μm; both electrode materials can be : Ti/Au, Al, electrode thickness > 50nm. Once the parallel metal electrodes are connected to the signal generator 3 , a coupled induced electric field can be generated between the cylindrical floating electrodes 2 . The metal electrode is prepared by photolithography and stripping process. The process is: photolithography by throwing glue, exposure, and development; then sputtering deposits metal and removes the glue to obtain the metal electrode. The chip substrate is P-type heavily doped silicon and silicon dioxide grown by thermal oxidation (thickness>100nm).

The manufactured chip 4 containing metal electrodes is inserted into a small groove 5 (as shown in FIG. 2 ), the small groove 5 contains a suspension 6 containing carbon nanotubes or semiconductor nanowires, and the chip 4 is immersed in the solution 6 . The external wire 7 is connected to the signal generator 3 , and the AC electric field can be applied to the electrodes by turning on the power of the signal generator, thereby generating an alternating induction electric field between the cylindrical floating-point electrodes 2 .

Under the action of an alternating electric field, a non-uniform electric field is generated between the electrodes, and carbon nanotubes or semiconductor nanowires are polarized under a non-uniform electric field, which will cause transient polarization on the surface and interior of carbon nanotubes or nanowires. The positive and negative charges of carbon nanotubes or nanowires form dipoles due to polarization, and form dipole moments in the solution.

In addition, when the dielectric particle is in a non-uniform electric field, it will be subjected to a two-dimensional electrophoretic force, which does not necessarily require the dielectric particle to be charged, and any particle will show a certain two-dimensional electrophoretic characteristic in the electric field, so the present invention is applicable to carbon nanotubes and nanowires. Both apply. The strength of DEP is mainly determined by the electrical characteristics of the medium and particles, and is affected by the size, shape and frequency of the electric field of the particles. Under the action of alternating current, carbon nanotubes or nanowires move rapidly to the electrode or to the carbon nanowires that have been lapped on the electrode due to the dipole moment and alternating electrophoretic force in the solution along the direction of electric field gradient decline. At the end of the tube, two or more carbon nanotubes or semiconductor nanowires form a Y-shaped bifurcated structure. Connected carbon nanotubes or semiconductor nanowires can form two or more Y-shaped bifurcated structures (as shown in FIG. 3 ).

Continue to apply the electric field, wait for a certain period of time, turn off the external power supply, take out the chip, and dry it to obtain a certain number of Y-shaped bifurcated structures between the cylindrical floating-point electrodes. , the number of Y-shaped bifurcated structures can be adjusted by controlling the intensity of the alternating electric field and the concentration of the carbon nanotube or semiconductor nanowire solution. The experimental parameters used are: a sinusoidal signal, a voltage of 10V (Vpp), a frequency of 16MHz, and a voltage application time of 20 minutes. Figure 4 shows the scanning electron micrographs of carbon nanotubes containing Y-shaped (Figure 4a) and T-shaped (Figure 4b) bifurcated structures.

The method provided by the present invention has been described above through detailed examples, and those skilled in the art should understand that within the scope not departing from the essence of the present invention, certain deformation or modification can be made to the present invention; its preparation method is not limited to the examples content disclosed in .

Claims (7)

1, the preparation method of a kind of CNT or nano wire bifurcation structure, its step comprises:

1) preparation chip, this chip comprises several floating-point electrodes between pair of parallel electrode and the parallel pole;

2) CNT and/or nano wire are dissolved in the organic solvent, and carry out ultrasonic dispersion, make the suspension of CNT and/or nano wire;

3) chip is immersed in the described suspension, on above-mentioned electrode, applies alternating current or direct current;

4) take out chip, dry up, between the floating-point electrode, obtain two or many CNTs and/or nano wire bifurcation structure.

2, the preparation method of CNT as claimed in claim 1 or nano wire bifurcation structure is characterized in that, in the described step 1), prepares metal electrode by photoetching in the microelectronic processing technology and lift-off technology, and the relative distance of parallel pole is 1-10 μ m.

3, the preparation method of CNT as claimed in claim 1 or 2 or nano wire bifurcation structure is characterized in that, in the described step 1), the adjacent electrode of floating-point electrode distance is 200-500nm.

4, the preparation method of CNT as claimed in claim 1 or nano wire bifurcation structure is characterized in that, described organic solvent is ethanol, acetone, n-hexane, isopropyl alcohol, dimethyl formamide, 1, the 2-dichloroethanes.

5, as the preparation method of claim 1 or 4 described CNTs or nano wire bifurcation structure, it is characterized in that described semiconductor nanowires is: simple substance element nano wire or compound semiconductor nano wire.

6, as the preparation method of claim 1 or 4 described CNTs or nano wire bifurcation structure, it is characterized in that described CNT is: SWCN, multi-walled carbon nano-tubes or SWCN are assembled the tube bank that forms.

7, the preparation method of CNT as claimed in claim 1 or nano wire bifurcation structure is characterized in that, in the described step 3), electrode applies alternating current, and the parameter area of the alternating current that specifically applies is V _PP=0.5-25V, frequency 1-10MHZ.

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