Diamond film boron oxide doping method
Technical Field
The invention relates to the technical field of hot wire chemical vapor deposition, and particularly provides a diamond film boron oxide doping method.
Background
Compared with the traditional electrode material, the boron-doped diamond electrode not only keeps the characteristics of high thermal conductivity, stability, high temperature resistance and the like of diamond, but also has a wider electrochemical window, low background current, adsorption inertia and the like. The boron-doped diamond electrode enables pure diamond to become a semiconductor, has stable electrochemical characteristics, has a wider potential window and lower background current, is not easy to adsorb organic matters or biological compounds, is resistant to acid and alkali corrosion, and has a self-cleaning function. Therefore, boron-doped diamond electrodes are widely used in the electrochemical field, wherein the boron-doped diamond electrodes are most widely studied in the sewage treatment field.
There are generally three common boron doping regimes: solid, liquid and gaseous boron sources, wherein liquid boron-containing substances are generally corrosive, and gaseous boron compounds are often toxic, so that non-toxic and non-corrosive solid boron doping modes have entered the research field.
CN201910925306.0 discloses a method for preparing boron-doped diamond by using a solid-state doping source, which aims to solve the problems that the gas boron source is unsafe and corrosive to equipment in the existing preparation method of the boron-doped diamond film. The invention discloses: firstly, preparing a doping source: grinding and mixing graphite powder and a boron source to obtain mixed powder, then putting the mixed powder into a tablet press, and pressing the mixed powder into a wafer or a square slice to obtain a solid-state doping source; the atomic ratio of boron element in the boron source to carbon element in the graphite powder is (0.001-0.1): 1; the boron source is boron powder or boron oxide powder; secondly, preparing the boron-doped diamond film: placing a substrate and a plurality of solid-state doping sources on a sample platform of a microwave plasma chemical vapor deposition device, uniformly distributing the plurality of solid-state doping sources on the periphery of the substrate, introducing hydrogen or mixed gas of the hydrogen and other gases, depositing for 30 min-50 h under the conditions that the hydrogen flow rate is 50 sccm-300 sccm, the substrate temperature is 400-1100 ℃, the solid-state doping source temperature is 600-1200 ℃, the pressure is 80 mbar-500 mbar and the microwave power is 1500-6000W, and growing a boron-doped diamond film on the surface of the substrate to obtain the substrate with the boron-doped diamond film growing on the surface, thereby completing the method for preparing the boron-doped diamond by using the solid-state doping sources.
Since the hot wire chemical vapor deposition (HFCVD) method has simple equipment, is easy to operate, and can grow high-quality diamond films at a high rate, the method is widely adopted so far, but the boron doping amount is difficult to control, so that the method is difficult to put into production on a large scale.
Disclosure of Invention
The technical task of the invention is to provide a diamond film boron oxide doping method aiming at the problems.
A boron oxide doping method for diamond film is characterized by that when the boron-doped diamond film is prepared by hot-wire vapour deposition method, several containers with same opening area are uniformly set on the periphery of substrate platform, the boron oxide powder is placed in the container, and when the hot wire is heated, the boron oxide powder in the container is heated to form high-temp. gasification so as to implement preparation of boron-doped diamond film.
The method realizes the control of the boron oxide doping concentration by setting the number of the containers. Since the area of the opening is determined, the surface area of the boron oxide participating in the gasification can be controlled by setting the number of the containers.
The container is a hollow vertical pipe, and the temperature of the boron oxide is adjusted by setting the height of the hollow vertical pipe, so that the gasification concentration of the boron oxide is adjusted.
The method comprises the following implementation steps:
1) selecting a substrate, and pretreating the substrate;
2) a plurality of hollow vertical pipes with equal opening area are uniformly arranged on the periphery of the substrate platform
3) Placing boron oxide powder in the vertical pipe;
4) electrifying and pressurizing, introducing carbon-containing gas, and entering nucleation and growth processes.
The substrate is made of titanium or silicon. The mismatching degree of silicon and diamond is small, a sound field BDD film is easy to be extended on the silicon in an epitaxial mode, and the Si/BDD electrode has good electrochemical characteristics, so that the silicon/BDD electrode is a substrate blank material which is most applied; the titanium has low cost and high mechanical strength, and can generate TiO if part of the diamond film falls off2The advantage of self-protection of the electrodes is achieved and is therefore appreciated.
The pretreatment process comprises cleaning and grinding. The surface of the substrate is uniformly ground by diamond powder and ultrasonically cleaned in deionized water, so that the nucleation and growth of the diamond on the surface of the substrate are facilitated.
The material of the hot wire is tungsten or tantalum. The temperature of the tungsten filament is generally 2000-2200 ℃, the maximum temperature of the tantalum filament can reach 2400 ℃, and the tungsten filament is two common hot filaments.
The carbon-containing gas is the mixture of methane, methanol, ethanol or acetone and hydrogen, wherein the concentration of the methane, the methanol, the ethanol or the acetone in the hydrogen is 0.1-2%.
The number of the hollow stand pipes is 3-12, the height of the hollow stand pipes is 3-10 mm, and the height from the substrate platform to the top of the stand pipes is increased.
The opening area of the container is 0.5-2 mm2。
Compared with the prior art, the diamond film boron oxide doping method has the following outstanding beneficial effects:
according to the invention, the plurality of containers with the same opening area are arranged on the periphery of the substrate platform, the boron oxide powder is contained in the containers, the quantity of the boron oxide participating in gasification can be controlled by controlling the quantity of the contained powder, and the distance between the boron oxide and the hot wire can be controlled by adopting the hollow vertical pipes with different heights as the containers, so that the contact temperature of the boron oxide is controlled, the gasification speed of the boron oxide is indirectly adjusted, a proper height and quantity are selected, and the boron doping concentration is controlled under the condition of certain other conditions, so that the boron is uniformly and efficiently doped in the deposition process.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1
A diamond film boron oxide doping method comprises the following implementation steps:
1) selecting a silicon substrate, uniformly coating diamond powder (with the diameter of 0.5 mu m) on the surface of the silicon substrate, and then ultrasonically cleaning the silicon substrate in deionized water;
2) 3 openings with the area of 2mm are uniformly arranged on the periphery of the substrate platform2A hollow riser having a height of 10 mm;
3) placing boron oxide powder in the vertical pipe;
4) tantalum wires are selected as filament heat sources, electrified and pressurized, and mixed gas of methane and hydrogen is introduced, wherein the ratio is 3: 100, carbonizing for 1 hour, nucleating for half an hour, and growing for 3 hours.
Example 2
1) Selecting a titanium substrate, uniformly coating diamond powder (with the diameter of 0.5 mu m) on the surface of the titanium substrate, and then ultrasonically cleaning the titanium substrate in deionized water;
2) the periphery of the substrate platform is uniformly provided with 12 openings with the area of 0.5mm2A hollow riser having a height of 3 mm;
3) placing boron oxide powder in the vertical pipe;
4) selecting tungsten filaments as a filament heat source, electrifying and pressurizing, introducing mixed gas of ethanol and hydrogen, wherein the ratio is 0.1: 100, carbonizing for 1 hour, nucleating for half an hour, and growing for 5 hours.
Compared with the diamond film not doped with boron, the diamond films obtained in the two embodiments are uniformly distributed, the structure is compact, and the conductivity is obviously improved. The effect of methanol or acetone is similar to ethanol or methane and is not repeated.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.