CN1590599A - Silicon nono-wire and its preparation method - Google Patents

Abstract

The invention discloses a silicon nanowire and a preparation method thereof. The silicon nanowire of the invention is composed of a single crystal silicon core and an amorphous oxide shell layer wrapped outside. Its preparation method is (1) use high-purity silicon powder and silicon dioxide powder, mix according to the weight ratio of 1:1, press into a sheet, put it in the source crucible of the ultra-high vacuum electron beam system and vacuumize it for later use (2) Select SiO ₂ /Si as the growth substrate of silicon nanowires, and use acetone and methanol solutions to ultrasonically clean it for 5 minutes, then dry it with high-purity nitrogen, put it into the pre-vacuum chamber of the electron beam system, and pump (3) Then transfer the substrate to the main vacuum chamber of the electron beam system with a background pressure of 2× ^10-10 mbar, heat it to 650-750°C, and after the temperature is stable, use the electron beam to evaporate the source crucible Si+SiO ₂ source, make silicon evaporate at a rate of 0.02nm/s, and deposit and grow on SiO ₂ /Si(111) or SiO ₂ substrate; (4) Cool the main vacuum chamber to room temperature, take out the substrate, The blue-gray or yellow film on its surface is the one-dimensional silicon nanowire.

Description

A kind of silicon nanowire and preparation method thereof

technical field

The invention relates to a nanometer material and a preparation method thereof, in particular to a silicon nanowire and a preparation method thereof.

Background technique

One-dimensional nanomaterials are important components of future nanoelectronic and optoelectronic devices, and have good prospects in both academic research and application development. Silicon nanowires are an important class of one-dimensional nanomaterials. At present, the methods for preparing silicon nanowires mainly include thermal evaporation, chemical vapor deposition (CVD), and laser ablation. In these methods, the preparation of silicon nanowires is generally carried out under the conditions of atmospheric pressure or low vacuum (background pressure ≥ ^{10 -2} mbar), and a growth temperature of 850°C to 1200°C. The further improvement of the quality and performance of nanowire products also brings many uncertain factors to the study of microscopic growth mechanism.

Contents of the invention

The object of the present invention is to provide a silicon nanowire and a preparation method thereof.

The silicon nanowire of the present invention is composed of a single-crystal silicon core with a diameter of 9-13nm and an amorphous oxide shell layer wrapped outside with a thickness of 5-9nm.

The single crystal silicon core is composed of (110) and (111) crystal planes with interplanar distances of 0.19 nm and 0.31 nm, respectively.

The growth orientation of the single crystal silicon nucleus is mainly [22 1].

The amorphous oxide shells are silicon oxide and silicon dioxide shells.

A method for preparing silicon nanowires, comprising:

(1) Preparation of silicon source for evaporation: be 99.99% silicon (Si) powder and 99.99% silicon dioxide (SiO ₂ ) powder with a purity of 99.99%, configure and stir in a ratio of 1:1 by weight, and then use The tablet press presses the Si+ _SiO2 powder into tablets, puts it in the source crucible of the ultra-high vacuum electron beam system to evacuate, and sets aside;

(2) Preparation of silicon nanowire growth substrate: select 100-600nm SiO ₂ /Si(111) or SiO ₂ as the growth substrate of silicon nanowire, and ultrasonically clean the growth substrate with analytical pure acetone and methanol solution respectively After 5 minutes, dry it with nitrogen, put it into the pre-vacuum chamber of the ultra-high vacuum electron beam system, and evacuate it;

(3) Growth of silicon nanowires: when the pressure in the pre-vacuum chamber reaches 1×10 ^-7 mbar, transfer the SiO ₂ /Si(111) or SiO ₂ substrate into the main vacuum chamber of the ultra-high vacuum electron beam system , heated to 650-750°C, and after the temperature stabilized, the Si+SiO ₂ source in the source crucible was evaporated by an electron beam to evaporate the silicon, and deposited and grown on the SiO ₂ /Si(111) or SiO ₂ substrate;

(4) After the main vacuum chamber is cooled to room temperature, take the substrate out of the main vacuum chamber, and the uniform blue-gray or yellow film on the surface of the substrate is the one-dimensional silicon nanowire.

In the above method for preparing silicon nanowires under ultra-high vacuum conditions, when the pressure of the pre-vacuum chamber reaches 1×10 ^-7 mbar, the SiO ₂ /Si(111) or SiO ₂ substrate is transferred to the ultra-high vacuum electron beam system When in the main vacuum chamber, the background pressure of the main vacuum chamber is 2×10 ^-10 mbar. The electron beam evaporation conditions are as follows: the accelerating voltage of the electron beam is 7kV; the emission current is 220mA; the evaporation rate is 0.02nm/s; the evaporation time is 7-10 minutes. The growth temperature of the silicon nanowires in the electron beam main vacuum chamber is preferably 700°C.

The method of the invention adopts an electron beam evaporation system to produce the silicon source required for the growth of silicon nanowires, uses 7kV electron beams to bombard and evaporate the Si+ _SiO2 source, and can prepare large-area silicon nanowires at a temperature of 700°C. In addition to the need for suitable source materials, the preparation of one-dimensional nanomaterials is also the key to the growth of one-dimensional nanomaterials by maintaining an appropriate and balanced temperature. Because, if the growth environment temperature is not uniform, a higher temperature gradient will terminate the growth of one-dimensional nanomaterials. The invention combines constant temperature control with an electron beam evaporation system, and successfully prepares large-area, high-quality and high-performance silicon nanowires under ultra-high vacuum conditions. The present invention develops a new application of electron beam evaporation technology, and provides a new method for large-scale preparation of silicon nanowires under ultra-high vacuum conditions. Using similar methods, it is likely to obtain more types of one-dimensional nanomaterials with unique properties. The study of one-dimensional nanomaterials has opened up new ideas, which is conducive to obtaining one-dimensional nanomaterial products with higher purity, and is of great significance for in-depth study of the growth mechanism of one-dimensional nanomaterials.

Description of drawings

Fig. 1 is the schematic diagram of the equipment device implementing the method of the present invention

Fig. 2 is the photomicrograph of the silicon nanowire of the present invention by scanning electron microscopy with different magnifications

Figure 3 is a photomicrograph of a single silicon nanowire of the present invention using a transmission electron microscope

Fig. 4 is a photomicrograph of a single silicon nanowire intermediate nucleus of the present invention inspected by a high-resolution transmission electron microscope

Fig. 5 is a photomicrograph of the result of using a high-resolution transmission electron microscope to examine the results of a single silicon nanowire of the present invention

Fig. 6 is the X-ray diffraction figure of silicon nanowire of the present invention

Fig. 7 is the X photoelectron energy spectrogram (XPS Si 2p spectrogram) of silicon nanowire of the present invention

Detailed ways

The equipment required for the specific implementation process of the present invention includes a fully automatic ultra-high vacuum electron beam evaporation system (Switzerland BALZERS ULS 400 system, the background pressure of the main vacuum chamber is 2× ^10-10 mbar) and a resistive constant temperature control system. The equipment is shown in Figure 1, including the pre-vacuum chamber 1 of the ultra-high vacuum electron beam system (ULS 400); the main vacuum chamber 2 of the ULS400 system; the sample 3; the heating device 4 configured by the ULS 400 system; Screen cover (constant temperature control system) 5; evaporation source crucible (Si+SiO ₂ source) 6; electron gun 7; film thickness and evaporation rate controller 8; quadrupole mass spectrometer 9; ULS 400 system temperature control and sample rotation device 10.

The specific method for preparing silicon nanowires is:

(1) Preparation of silicon source for evaporation: use a silicon (Si) powder with a purity of 99.99% and a silicon dioxide (SiO ₂ ) powder with a purity of 99.99%, configure and stir in a ratio of 1:1 by weight, and then Press the Si+ _SiO2 powder into tablets with an ordinary tablet press, put them in the source crucible 6 of the ultra-high vacuum electron beam system to evacuate, and set aside.

(2) Preparation of silicon wire growth substrate: select 100nm SiO ₂ /Si(111) as the growth substrate of silicon nanowire, ultrasonically clean the growth substrate with analytical pure acetone and methanol solution for 5 minutes, and then use high-purity After being blown dry with nitrogen, immediately put it into the pre-vacuum chamber 1 of the ultra-high vacuum electron beam system, and evacuate it.

(3) Growth of silicon wires: when the pressure in the pre-vacuum chamber 1 reaches 1×10 ^-7 mbar, transfer the SiO ₂ /Si(111) substrate to the main vacuum chamber 2 (the background pressure is 2×10 ^-10 mbar), first use the resistive program controllable heating screen cover 5 (constant temperature control system) and the heating device 4 configured in the ULS 400 system to heat together, so that the temperature in the growth area reaches 700 ° C, after the temperature is stable, use the electron beam evaporation source The Si+ _SiO2 source in the crucible 6 evaporates silicon, the accelerating voltage of the electron beam is 7kV; the emission current is 220mA; the evaporation rate is 0.02nm/s, and the deposition and growth on the _SiO2 /Si(111) substrate 8 minute.

(4) The main vacuum chamber 2 was cooled to room temperature, and then the substrate was taken out of the main vacuum chamber 2, and it was found that a large area of uniform blue-gray film was formed on the surface of the substrate, which was one-dimensional silicon nanowires.

Through the analysis of the following methods, it can be proved that a large amount of one-dimensional silicon nanowires can be prepared by adopting the preparation method described in the present invention.

Adopt the preparation method described in the present invention, the prepared one-dimensional silicon nanowire, through the scanning electron microscope inspection of different magnifications, as shown in Figure 2, the result shows that a large amount of one-dimensional nanowires are formed, and its length is 1～4 μ m , similar images were obtained in different regions; a single silicon nanowire was examined by a transmission electron microscope, as shown in Figure 3, and the results showed that the one-dimensional silicon nanowire consisted of a single crystal core (about 10nm in diameter) ), and an amorphous oxide shell (thickness about 5-9nm) wrapped on the outside; the core of a single silicon nanowire was examined by a high-resolution transmission electron microscope, as shown in Figure 4, and the results showed that the single silicon nanowire in the middle The crystalline core is composed of (110) and (111) lattice planes with interplanar spacings of 0.19nm and 0.31nm, respectively; a single silicon nanowire was examined by high-resolution transmission electron microscopy, as shown in Figure 5. The results show that the The angles between the growth direction of the silicon nanowire and the [110] and [111] directions are 19 degrees and 54 degrees, respectively, which means that the growth direction of the silicon nanowire is [22 1]. The illustration in the upper right corner of Figure 5 is The electron diffraction pattern of the prepared silicon nanowires shows the main crystal plane family of the silicon nanowires; as shown in Figure 6, the X-ray diffraction pattern of the prepared silicon nanowires further proves the crystal plane family of the silicon nanowires; As shown in Figure 7, the X-ray photoelectron spectrum (XPS Si 2p spectrum) of the prepared silicon nanowires proves that the prepared silicon nanowires contain pure Si cores, and SiO and SiO ₂ oxide shells.

Claims (8)

1, a kind of silicon nanowires is that the single crystal silicon core of 9～13nm and the thickness that is wrapped in the outside are that the amorphous oxides shell of 5～9nm is formed by diameter.

2, silicon nanowires according to claim 1 is characterized in that: described single crystal silicon core is made up of (110) and (111) crystal face that interplanar distance is respectively 0.19nm and 0.31nm.

3, silicon nanowires according to claim 1 is characterized in that: the growth orientation of described silicon single crystal nuclear is mainly [221].

4, silicon nanowires according to claim 1 is characterized in that: described amorphous oxides shell is silicon oxide and silica shell.

5, a kind of preparation method of silicon nanowires comprises:

(1) evaporation is with the preparation in silicon source: with purity is that 99.99% silicon (Si) powder and purity are 99.99% silicon-dioxide (SiO ₂) powder, be to be configured at 1: 1 to stir evenly by weight proportion, use tabletting machine Si+SiO then ₂The powder tablet forming is placed in the source crucible of ultrahigh vacuum(HHV) electron beam system and vacuumizes, and is standby;

(2) preparation of silicon nanowires growth substrates: select 100～600nm SiO for use ₂/ Si (111) or SiO ₂As the growth substrates of silicon nanowires, successively use analytical pure acetone and methanol solution to growth substrates difference ultrasonic cleaning 5 minutes, after drying up with nitrogen again, put into the prechamber of ultrahigh vacuum(HHV) electron beam system, vacuumize;

(3) growth of silicon nanowires: when the pressure of prechamber reaches 1 * 10 ^-7Behind the mbar, SiO ₂/ Si (111) or SiO ₂Substrate passes in the main vacuum chamber of ultrahigh vacuum(HHV) electron beam system, is heated to 650～750 ℃, behind the temperature-stable, and the Si+SiO in the crucible of deposited by electron beam evaporation source again ₂The source is evaporated silicon, and at SiO ₂/ Si (111) or SiO ₂Deposition growing on the substrate;

(4) after main vacuum chamber is cooled to room temperature, substrate is taken out from main vacuum chamber,, be the one dimension silicon nanowires at uniform pewter of substrate surface or yellow film.

6, the preparation method of silicon nanowires according to claim 5 is characterized in that: described pressure when prechamber reaches 1 * 10 ^-7Behind the mbar, SiO ₂/ Si (111) or SiO ₂When substrate passed in the main vacuum chamber of ultrahigh vacuum(HHV) electron beam system, the background pressure of main vacuum chamber was 2 * 10 ^-10Mbar.

7, the preparation method of silicon nanowires according to claim 5 is characterized in that: the acceleration voltage of electron beam is 7kV; Transmitter current is 220mA; Vaporator rate is 0.02nm/s; Evaporation time is 7～10 minutes.

8, the preparation method of silicon nanowires according to claim 5 is characterized in that: described silicon nanowires is 700 ℃ in the growth temperature of electron beam main vacuum chamber.

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