CN104762608B - A preparation method of horizontal CdS nanowire array with controllable growth direction - Google Patents

Abstract

The invention relates to a preparation method of a horizontal CdS nanowire array whose growth direction can be controlled, and belongs to the technical field of preparation of one-dimensional semiconductor nanometer materials. The present invention adopts a simple method for the first time to realize the controllable growth of cadmium sulfide nanowires in the direction, and the obtained nanowires can be tens of microns in length and about 100 nanometers in diameter. The technology of the invention is simple, convenient to control, and convenient for large-scale production and application. At the same time, the designed process and the prepared finished product of the present invention will have important application value in basic physics research and integration of nanoscale functional devices.

Description

A preparation method of horizontal CdS nanowire array with controllable growth direction

technical field

The invention relates to a preparation method of a horizontal CdS nanowire array whose growth direction can be controlled, and belongs to the technical field of preparation of one-dimensional semiconductor nanometer materials.

technical background

Cadmium sulfide (CdS) is a typical II-VII semiconductor compound with a bandgap of 2.42eV at room temperature. It has excellent luminescence performance and photoelectric conversion characteristics, and has important application value in the fields of light-emitting diodes, solar cells, and nanowire lasers. So far, people have developed a variety of methods for synthesizing one-dimensional semiconductor nanowires, such as traditional chemical vapor deposition, hydrothermal method, physical stretching method and so on. Especially in the traditional chemical vapor deposition method, the growth direction of the nanowires is not fixed under the joint action of substrate lattice, air flow, thermal disturbance and other factors, resulting in the orientation of the prepared nanowires is often disorderly; this It brings great difficulties for the next step of nanowire system integration.

In the prior art, there is no relevant report on the preparation of CdS nanowire arrays using sapphire as a substrate.

Invention content:

Aiming at the deficiencies of the prior art, the present invention provides a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled by pure components, which solves the problem that a high-quality horizontal CdS nanowire array cannot be prepared by a one-step method in the prior art .

A method for preparing a horizontal CdS nanowire array with controllable growth direction of the present invention comprises the following steps:

A horizontal tube furnace with an air inlet and an air outlet is used as a reaction furnace, and a sapphire with catalyst gold on the surface is used as a substrate; the substrate is placed at the end of the reaction furnace near the gas outlet; the CdS powder is placed in the reaction furnace Middle; vacuumize, feed carrier gas, heat up to the heating temperature of the CdS powder is 750-850°C, preferably 770-830°C, more preferably 790-810°C, and the heating temperature of the substrate is 200-600°C, preferably 250-500°C, more preferably 300-400°C; carrier gas carrying CdS vapor is deposited on the substrate to obtain CdS nanowires, then cooled with the furnace, and ultrasonically oscillated to obtain a horizontal CdS nanowire array on the substrate; The catalyst gold is distributed in stripes or dots on the sapphire; the flow rate of the carrier gas is 10-100 sccm, preferably 30-80 sccm, more preferably 40-60 sccm; during deposition, the pressure in the furnace is controlled to be 100-700 mbar, Preferably it is 350-600 mbar, more preferably 400-550 mbar.

In the present invention, the sapphire with catalyst gold on the surface is used as the substrate, and the substrate can be annealed to ensure better effect; the annealing conditions are: temperature 500-800°C, time 10-30min.

The invention relates to a method for preparing a horizontal CdS nanowire array with controllable growth direction, wherein the purity of the CdS powder is ≥99.99%; preferably, the purity is ≥99.999%.

The invention relates to a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled, and the deposition time is controlled to be 1-3 hours.

The invention discloses a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled. The ultrasonic oscillation is to place the substrate deposited with CdS nanowires in isopropanol or deionized water, and control the ultrasonic power to 40-120W. , the time is 1-5 minutes.

The invention discloses a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled. After the horizontal CdS nanowire array is obtained on the substrate, the CdS nanowire array grown along the horizontal direction can be obtained by washing and drying with deionized water. .

The present invention is a method for preparing a horizontal CdS nanowire array with controllable growth direction. The sapphire with catalyst gold on the surface is prepared by the following scheme:

Using sapphire as the substrate, after the sapphire is subjected to high-temperature annealing treatment, after the sapphire is coated with a layer of positive or negative photoresist, a strip or dot pattern of a set size is prepared on the substrate by photolithography; then A gold film with a thickness of 5-10nm is plated on the prepared substrate; after the gold film is coated, the substrate is soaked in acetone at 40-60°C for 5-10min, rinsed with deionized water, and dried , the sapphire with catalyst gold on the surface can be obtained;

or

Using sapphire as the substrate, after the sapphire is subjected to high-temperature annealing treatment, after the sapphire is coated with a layer of PMMA (polymethyl methacrylate), the strip or dot pattern of a set size is prepared on the substrate by electron beam exposure ; Then plate a layer of gold film with a thickness of 5-10nm on the above substrate; after coating the gold film, soak the substrate in acetone at 40-60°C for 5-10min, rinse with deionized water, and dry , the sapphire with catalyst gold on the surface can be obtained; the temperature of the high-temperature annealing treatment is 1200-1600° C., and the time is 3-10 hours.

The invention discloses a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled. The high-temperature annealing treatment of the sapphire is as follows: annealing at 1200-1600° C. for 3-10 hours in an air atmosphere.

The invention relates to a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled, and the carrier gas is argon or a mixed gas of argon and hydrogen.

The invention discloses a method for preparing a horizontal CdS nanowire array whose growth direction can be controlled. The prepared cadmium sulfide nanowire array is a horizontal linear array whose chemical formula is CdS. Its length is 10-50 microns, preferably 20-30 microns; its diameter is 100-500 nm, preferably 150-300 nm.

Principles and advantages

The invention skillfully utilizes the property that some surfaces of the sapphire substrate are thermally unstable and can spontaneously form channels at high temperatures. Through reasonable parameter control, the CdS nanowires grow parallel to the substrate as much as possible when the nanowires are prepared by the chemical vapor deposition method. Due to the particularity of the substrate used, especially when there is a channel on the substrate, the nanowires will preferentially grow along the direction of the channel. At the same time, the CdS nanowires grown along other directions, due to the weak binding force with the substrate (compared to the nanowires grown parallel to the substrate), can easily be processed by ultrasonic vibration to achieve the parallel with the substrate. The substrate on which the CdS nanowires are grown is separated; resulting in a horizontal CdS nanowire array.

The invention has simple technology and convenient control, and mainly uses the chemical vapor deposition method to synthesize the horizontal CdS nanowire array in one step. The obtained samples are arranged in an array, and the length of the nanowires can reach 50um. Under laser excitation with a wavelength of 488nm, a photoluminescence peak with a half-maximum width of less than 20nm near 510nm can be observed, indicating that the prepared CdS nanowire array has good crystal quality. This one-dimensional semiconductor nanowire array with high crystallinity will have important applications in the preparation of micro-nano devices and system integration.

Description of drawings:

Fig. 1 is the SEM photograph of the CdS nanowire prepared by comparative example 1;

Figure 2a is a photo of the horizontal CdS nanowire array prepared in Example 1 under a Carl Zeiss optical microscope;

Fig. 2b is the SEM picture of the horizontal CdS nanowire array prepared in embodiment 1;

FIG. 2c is a photoluminescence spectrum diagram of the horizontal CdS nanowire array prepared in Example 1. FIG.

Fig. 3 is a photograph of the dispersed CdS sample prepared in Comparative Example 2 under a Carl Zeiss optical microscope.

Figure 4 is a schematic diagram of the equipment used in the present invention and its operation.

From the SEM picture in Figure 1, it can be seen that the growth direction of the CdS nanowires prepared by the traditional method is chaotic.

It can be seen from Fig. 2a and Fig. 2b that the CdS nanowire prepared by the present invention grows along a specific direction, and the length of the nanowire can reach 30um.

It can be seen from the photoluminescence spectrum in Fig. 2c that the CdS nanowire array prepared by the present invention has high crystal quality and good optical properties.

It can be seen from Figure 3 that the prepared CdS samples are mostly nanobelts with few lines.

It can be seen from Figure 4 that the quartz boat filled with CdS medicine is located at the heating center of the horizontal tube furnace, and the substrate is located at the end of the low temperature zone of the tube furnace near the gas outlet.

detailed description:

Now in conjunction with accompanying drawing, the present invention will be further described:

Comparative Example 1: Take a Si wafer as a substrate, cut it into 10×10mm size, ultrasonically wash it in acetone solution for 20 minutes, rinse it with deionized water, take it out and dry it in an oven at 50°C. Then a 10nm gold film was evaporated on the Si substrate by electron beam evaporation coating method. A certain amount of CdS medicine is loaded into a quartz boat, placed in the center of the tube furnace, and the Si substrate is placed in the low temperature zone of the tube furnace. The carrier gas is introduced, and the temperature is raised until the central temperature of the tube furnace is 810°C. At this time, the temperature at the position of the Si substrate is 400°C, and the reaction is performed at a constant temperature for a period of time. After the reaction was over, the heating furnace was naturally cooled to room temperature. Under the scanning electron microscope, it can be found that the growth direction of the prepared cadmium sulfide nanowires is chaotic.

Comparative example 2:

Take the sapphire substrate, cut it into 10×10mm size, ultrasonically wash it in acetone solution for 20min, rinse it with deionized water, take it out and dry it in an oven at 50°C. Put the sapphire substrate in a high-temperature annealing furnace for annealing treatment (the annealing temperature is 1200°C, and the time is 10h), and then coat a layer of negative photoresist (DNR-L300) on the annealed substrate and pass Prepare a 5×50um strip pattern on the sapphire substrate by photolithography; then plate a layer of gold film with a thickness of 10nm on the substrate; after coating the gold film, soak the substrate in acetone at 50°C 10 minutes, rinsed with deionized water, and dried to obtain sapphire with catalytic gold on the surface.

Take a certain amount of CdS medicine into the quartz boat, put it in the center of the tube furnace, and put the sapphire substrate in the low temperature zone of the tube furnace. Vacuumize, feed argon gas at a flow rate of 50sccm, control the pressure to 50mbar, and raise the temperature to the center temperature of the tube furnace to 800°C. At this time, the temperature at the position of the sapphire substrate is 380°C. After 2 hours of constant temperature reaction; The furnace was naturally cooled to room temperature. The prepared samples were taken out and scattered on the cover glass for observation, and it was found that the prepared samples were mostly nanobelts and less nanowires.

Example 1:

Take the sapphire substrate, cut it into 10×10mm size, ultrasonically wash it in acetone solution for 20min, rinse it with deionized water, take it out and dry it in an oven at 50°C. Put the sapphire substrate in a high-temperature annealing furnace for annealing treatment (the annealing temperature is 1200°C, and the time is 10h), and then coat a layer of negative photoresist (DNR-L300) on the annealed substrate and pass Prepare a 5×50um strip pattern on the sapphire substrate by photolithography; then plate a layer of gold film with a thickness of 10nm on the substrate; after coating the gold film, soak the substrate in acetone at 50°C 10 minutes, rinsed with deionized water, and dried to obtain sapphire with catalytic gold on the surface.

Take a certain amount of CdS medicine into the quartz boat, put it in the center of the tube furnace, and put the sapphire substrate in the low temperature zone of the tube furnace. Vacuumize, feed argon gas at a flow rate of 50sccm, control the pressure to 500mbar, and raise the temperature to the center temperature of the tube furnace to 800°C. At this time, the temperature at the position of the sapphire substrate is 380°C. After 2 hours of constant temperature reaction; The furnace was naturally cooled to room temperature. The prepared sample was taken out and placed in an isopropanol solution for 1 min and ultrasonic power was 40W, and then washed with deionized water and dried to obtain a CdS nanowire array grown along the horizontal direction. The photo under the Carl Zeiss optical microscope is shown in Figure 2a; Figure 2b is the corresponding photo under the scanning electron microscope; Figure 2c is the photoluminescence photo under 488nm laser excitation, the central wavelength of the spectrum is 510nm, and the full width at half maximum is about It can be seen that the crystalline quality of the prepared CdS nanowires is good.

Example 2:

Take the sapphire substrate, cut it into 10×5mm size, ultrasonically wash it in acetone solution for 20min, rinse it with deionized water, take it out and dry it in an oven at 50°C. Put the sapphire substrate in a high-temperature annealing furnace for annealing treatment (the annealing temperature is 1600°C, and the time is 3h), and then coat a layer of negative photoresist (DNR-L300) on the annealed substrate and pass Prepare a 5×50um strip pattern on the sapphire substrate by photolithography; then plate a layer of gold film with a thickness of 5nm on the substrate; after coating the gold film, soak the substrate in acetone at 50°C 10 minutes, rinsed with deionized water, and dried to obtain sapphire with catalytic gold on the surface.

Take a certain amount of CdS medicine into the quartz boat, put it in the center of the tube furnace, and put the sapphire substrate in the low temperature zone of the tube furnace. Vacuumize, feed argon gas at a flow rate of 40sccm, control the pressure to 550mbar, and raise the temperature to the center temperature of the tube furnace to 810°C. At this time, the temperature at the position of the sapphire substrate is 400°C. After constant temperature reaction for 1h; The furnace was naturally cooled to room temperature. The prepared sample was taken out and placed in deionized water for 1 min and ultrasonic power was 40W, and then washed with deionized water and dried to obtain a horizontally grown nanowire array. The reaction time is short, and the length of the prepared nanowires is relatively short.

Example 3:

Take the sapphire substrate, cut it into 10×5mm size, ultrasonically wash it in acetone solution for 20min, rinse it with deionized water, take it out and dry it in an oven at 50°C. Put the sapphire substrate in a high-temperature annealing furnace for annealing treatment (the annealing temperature is 1400°C, and the time is 8h), and then coat a layer of negative photoresist (DNR-L300) on the annealed substrate and pass Prepare a 5×50um strip pattern on the sapphire substrate by photolithography; then plate a layer of gold film with a thickness of 8nm on the substrate; after coating the gold film, soak the substrate in acetone at 50°C 10 minutes, rinsed with deionized water, and dried to obtain sapphire with catalytic gold on the surface.

Take a certain amount of CdS medicine into the quartz boat, put it in the center of the tube furnace, and put the sapphire substrate in the low temperature zone of the tube furnace. Vacuumize, feed argon gas at a flow rate of 60sccm, control the pressure to 400mbar, and raise the temperature to the center temperature of the tube furnace at 790°C. At this time, the temperature at the position of the sapphire substrate is 350°C. After constant temperature reaction for 1h; The furnace was naturally cooled to room temperature. The prepared sample was taken out and placed in deionized water for 1 min and ultrasonic power was 40W, and then washed with deionized water and dried to obtain a horizontally grown nanowire array.

It can be seen from Example 1 and Comparative Example 2 that a high-quality horizontal CdS nanowire array can only be obtained under the synergistic effect of the selection of the substrate, the evaporation temperature of the CdS powder, the deposition temperature, the flow rate of the carrier gas, and the pressure in the furnace. In Comparative Example 2, since the pressure in the furnace was not within the range defined by the present invention during deposition, the resulting samples were mostly nanobelts and less nanowires.

Claims (6)

1. A method for preparing a horizontal CdS nanowire array with controllable growth direction, characterized in that it comprises the following steps: A horizontal tube furnace with an air inlet and an air outlet is used as a reaction furnace, and a sapphire with catalyst gold on the surface is used as a substrate; the substrate is placed at the end of the reaction furnace near the gas outlet; the CdS powder is placed in the reaction furnace middle; vacuumize, feed the carrier gas, and raise the temperature until the heating temperature of the CdS powder is 750-850°C, and the heating temperature of the substrate is 200-400°C; the carrier gas carries CdS vapor and deposits on the substrate to obtain CdS nanowires, Then cool down with the furnace and vibrate ultrasonically to obtain a horizontal CdS nanowire array on the substrate; the catalyst gold is distributed in stripes or dots on the sapphire; the flow rate of the carrier gas is 10-100 sccm; during deposition, the furnace is controlled The internal air pressure is 100-700mbar; Sapphire with catalyst gold on its surface was prepared by the following protocol: With sapphire as the substrate, the sapphire is subjected to high-temperature annealing treatment first, and then coated with a layer of positive or negative photoresist, and a strip or dot pattern of a set size is prepared on the substrate by photolithography, and then a layer is coated. A gold film with a thickness of 5-10nm; after coating the gold film, soak the substrate in acetone at 40-60°C for 5-10 minutes, rinse it with deionized water, and dry it to get a sapphire with catalyst gold on the surface ; or Using sapphire as the substrate, the sapphire is subjected to high-temperature annealing treatment first, and then coated with a layer of PMMA, and the strip or dot pattern of the set size is prepared on the substrate by electron beam exposure method, and then the thickness of the layer is 5-10nm. Gold film; after coating the gold film, soak the substrate in acetone at 40-60°C for 5-10 minutes, rinse it with deionized water, and dry it to get sapphire with catalyst gold on the surface; The high-temperature annealing treatment for sapphire is to anneal at 1200-1600° C. for 3-10 hours in an air atmosphere. 2. The method for preparing a horizontal CdS nanowire array with controllable growth direction according to claim 1, characterized in that: the purity of the CdS powder is ≥99.99%. 3. the preparation method of a kind of growth direction controllable horizontal CdS nanowire array according to claim 2 is characterized in that: the horizontal tube furnace with air inlet and gas outlet is used as reaction furnace, with surface band The sapphire with catalyst gold is used as the substrate; the substrate is placed at the end of the reaction furnace near the gas outlet; the CdS powder is placed in the reaction furnace; the vacuum is pumped, the carrier gas is introduced, and the heating temperature of the CdS powder is 770-830 °C, the heating temperature of the substrate is 250-400 °C; the carrier gas carries CdS vapor and deposits on the substrate to obtain CdS nanowires, then cools with the furnace, and ultrasonically vibrates to obtain a horizontal CdS nanowire array on the substrate; The catalyst gold is distributed on the sapphire in stripes or dots; the flow rate of the carrier gas is 30-80 sccm; during deposition, the pressure in the furnace is controlled to be 350-600 mbar. 4. the preparation method of a kind of growth direction controllable horizontal CdS nanowire array according to claim 3 is characterized in that: the horizontal tube furnace with air inlet and gas outlet is used as the reaction furnace, and the surface belt The sapphire with catalyst gold is used as the substrate; the substrate is placed at the end of the reaction furnace near the gas outlet; the CdS powder is placed in the reaction furnace; the vacuum is pumped, the carrier gas is introduced, and the heating temperature of the CdS powder is 790-810 °C, the heating temperature of the substrate is 300-400 °C; the carrier gas carries CdS vapor and deposits on the substrate to obtain CdS nanowires, then cools with the furnace, and ultrasonically vibrates to obtain a horizontal CdS nanowire array on the substrate; The catalyst gold is distributed on the sapphire in stripes or dots; the flow rate of the carrier gas is 40-60 sccm; during deposition, the pressure in the furnace is controlled to be 400-550 mbar. 5. The method for preparing a horizontal CdS nanowire array with controllable growth direction according to any one of claims 1-4, characterized in that: the deposition time is controlled to be 1-3 hours. 6. The method for preparing a horizontal CdS nanowire array with controllable growth direction according to any one of claims 1-4, characterized in that: the ultrasonic oscillation is to place the substrate on which the CdS nanowires are deposited In isopropanol or deionized water, control the ultrasonic power to 40-120W for 1-5 minutes.