CN1323051A - Prepn of ordered nanometer carbon pipe array on silicon chip - Google Patents

Abstract

The method for preparing an ordered carbon nanotube array on a silicon substrate is a method for preparing a field emission cathode, which belongs to the technical field of flat panel display device manufacturing. (2) Using the anodic oxidation method in the electrochemical reaction to obtain a nanopore array with an adjustable pore size of 10-100 nanometers and an orderly arrangement of pores; (3) Thinning the bottom of the nanopore and the silicon substrate due to oxidation The thickness of the aluminum oxide insulating layer formed is to make it penetrate and keep the remaining aluminum layer intact. The ferrous sulfate solution is electrolyzed to obtain iron catalyst particles or nanowires deposited at the bottom of the hole; (4) carbon source gas and diluent gas are used in nanometer Cleavage in the hole to form a multi-wall carbon nanotube array with adjustable length and diameter and good contact with the silicon substrate; (5) Treat the reaction product with alkali solution to obtain the carbon nanotube array.

Description

Preparation method of ordered carbon nanotube array on silicon substrate

The invention relates to a preparation technology of a field emission cathode, which belongs to the technical field of flat panel display device manufacture.

Since the field emission flat panel display (Field Emission Display Panel) works almost the same as the traditional cathode ray tube (Cathode Ray Tube), it has all the advantages of the traditional cathode ray tube. In addition, the field emission flat panel display device also has the characteristics of low power consumption, low voltage, thinner, flatter, and can work under harsh conditions. The field emission cathode is the core of the field emission flat panel display device, which provides the working current for the field emission flat panel display device. According to the working mechanism of the field emission cathode, it can be roughly divided into the following two different types: microtip array emission (Microtip Array) and thin film (ThinFilm) emission. In the microtip array emission, according to the different materials, it includes molybdenum cone array and silicon cone array. Thin film emission is mainly based on diamond thin film. Among foreign electronic companies developing field emission display devices, Pixtech, Futuba, Candescent, Micron, Motorola, Raytheon and FED companies mainly use Microtip Array (Microtip Array) as field emission cathode, and FEPET uses Diamond Thin Film (Diamond Thin Film) as source of electron emission.

In the late 1990s, the discovery of carbon nanotubes and the development of their preparation technology provided a good opportunity for the breakthrough development of field emission display devices. Carbon nanotubes are an important nanomaterial, which has many unique properties, among which the tip field emission performance provides the possibility for the application of carbon nanotubes in field emission flat panel display devices. In the application of field emission display devices, carbon nanotube arrays are required to have a large emission current density, and at the same time, they should have good vacuum performance. The carbon nanotube field emission cathode is usually prepared by an electric arc method, and the produced carbon nanotubes are made into a hydrosol, and then coated on a desired substrate. South Korea's Samsung Corporation used this method to develop a 4.5" field emission display device in 1999. In 2000, Samsung demonstrated a 9" field emission flat panel display device in the form of a triode. The Taiwan Industrial Research Institute has developed a monochrome field emission display screen with a screen coating technology with a resolution of 64×256 pixels. Japan's Ise company and Mie University cooperated to develop a high-brightness light source for field emission. Although the arc method has the advantages of relatively simple preparation process and easy realization of large-area transplantation, it is difficult to control the uniformity of the carbon nanotubes, and it is also difficult to control the height and orientation of the carbon nanotubes in the field emission cathode prepared by this method. . This will make the brightness of the carbon nanotube field emission display uneven, and the driving voltage among the pixels will be inconsistent.

The purpose of the present invention is to provide a method for preparing an ordered carbon nanotube array on a silicon wafer that can meet the requirements of high brightness and uniformity of field emission flat panel display devices and is compatible with the existing electric vacuum process and CRT manufacturing process.

The preparation method of the carbon nanotube array proposed by the present invention comprises:

①. Deposit a smooth aluminum film with a thickness of 5 microns to 50 microns on a silicon substrate;

②. Using the anodic oxidation method in the electrochemical reaction to obtain a nanopore array with an adjustable pore diameter of 10-100 nanometers and an orderly arrangement of pores;

③. Thinning the thickness of the aluminum oxide insulating layer formed by oxidation at the bottom of the nanopore and the silicon substrate, making it penetrate, and keeping the remaining aluminum layer intact, electrolyzing the ferrous sulfate solution to obtain iron catalyst particles or nanowires deposited at the bottom of the hole;

④. Use carbon source gas and diluent gas to crack in the nanopore to form a multi-walled carbon nanotube array with adjustable length and diameter and good contact with the silicon substrate;

⑤. The reaction product is treated with an alkali solution to obtain a carbon nanotube array.

The aluminum film deposited on the silicon wafer has a roughness of less than 0.2 microns. The carbon source gas is acetylene, the diluent gas is hydrogen, argon, nitrogen, and the molar ratio of the carbon source to the diluent gas is in the range of 0.1 to 0.5; the catalyst is iron, nickel, and cobalt, and the reaction temperature is 650 to 750°C, and the heating rate used is 20～30℃/min, keep warm for 0.5～3 hours

The preparation method proposed by the present invention has the following characteristics compared with other methods for growing carbon nanotubes on silicon substrates:

①. The grown carbon nanotube array has high purity and orderly arrangement. All carbon nanotubes are perpendicular to the substrate surface, which is conducive to the field emission of electrons;

②. The orientation, height and density of carbon nanotubes obtained by this method are uniform, and the designed surface electric field distribution and emission current density can be obtained by optimizing these parameters;

③. At the same time, using this method can obtain a large-area uniformly distributed carbon nanotube array, which provides a technological possibility for the preparation of large-scale field emission display devices;

④. Since the carbon nanotube array prepared by this method is grown on a silicon substrate with a low expansion coefficient, it is more conducive to the packaging and vacuum maintenance of the entire field emission display device;

⑤. The method for growing carbon nanotube arrays can be compatible with microelectronic processing technology, and provides convenience for integration and selection of device preparation technology.

Embodiments of the present invention are as follows:

1. Deposit aluminum film on silicon wafer:

a. Soak the n-type silicon wafer in hydrofluoric acid for 2 minutes, wash and dry;

b. Evaporate an aluminum film on a silicon wafer with an electron beam, the evaporation thickness is 20 microns, and the substrate temperature is 300°C;

2. Preparation of Nanopore Sequence with Pore Diameter of 20nm (Adjustable) and Orderly Arrangement by Anodic Oxidation

List:

a. Put the aluminum film into the electrolytic cell and soak it in ethanol for 30 minutes;

b. Use 0.3 molar sulfuric acid aqueous solution as the electrolyte, graphite as the cathode, and the distance between the electrodes is 50

mm, the reaction voltage is 20 volts, the reaction temperature is 20°C, and the reaction time is 2.5 hours;

c. After the reaction is completed, the voltage is interrupted, and the reacted silicon wafer is kept in sulfuric acid solution for 40 minutes;

3. After cleaning, use a saturated aqueous solution of ferrous sulfate plus 0.2 mole of boric acid as the electrolyte, and use 18 volts

50 Hz superimposed 2 V DC as the deposition voltage, connected the silicon wafer to the negative electrode, and deposited for 5 minutes;

4. The deposited silicon wafers were subjected to chemical vapor deposition and treated with pure hydrogen at 500°C for 1 hour,

 Heating up to 700°C, at a pressure of 200 Torr, a flow rate of 200 ml/min, and a composition of 9:1

In the mixed gas of nitrogen and acetylene, after 2 hours of deposition, it is lowered to room temperature with the furnace under pure nitrogen;

5. The well-reacted samples were treated with aqueous sodium carbonate solution for 5 hours to obtain neatly arranged and evenly spaced samples.

 Multi-walled carbon nanotubes with a diameter of 20±5 nm that are uniform, vertical to the surface of the silicon wafer, and have a small top height deviation

array.

Claims (4)

1. the preparation method of an ordered nanometer carbon pipe array on silicon chip is characterized in that its preparation method is as follows:

(1) deposit thickness is 5 microns to 50 microns an aluminium film on the silicon chip;

(2) with the anode oxidation method in the electrochemical reaction obtain that the aperture is adjustable in 10～100 nanometers, the hole arranges orderly nanohole array;

(3) attenuate nano-pore bottom and silicon chip because the thickness of the alumina insulating layer that oxidation forms makes its perforation, and keep the residue aluminium lamination complete, the electrolysis copperas solution obtains being deposited on the iron catalyst particle or the nano wire of hole bottom;

(4), form length, diameter is adjustable, contacts good multiple-wall carbon nanotube array with silicon chip with carbon-source gas and diluent gas cracking in nano-pore;

(5) product is handled with aqueous slkali, obtained nanometer carbon pipe array.

2. the preparation method of ordered nanometer carbon pipe array on silicon chip according to claim 1 is characterized in that its roughness of aluminium film that deposits is lower than 0.2 micron on silicon chip.

3. the preparation method of ordered nanometer carbon pipe array on silicon chip according to claim 1 and 2 is characterized in that carbon-source gas is an acetylene, and diluent gas is hydrogen or nitrogen or argon gas, and the mol ratio of carbon-source gas and diluent gas is in 0.1～0.5 scope.

4. the preparation method of ordered nanometer carbon pipe array on silicon chip according to claim 1 and 2 is characterized in that catalyst is iron or nickel or cobalt, and reaction temperature is 650～750 ℃.Used heating rate is 20～30 ℃/min.