Synthetic single crystal diamond is the material for making single crystal knife. Now it has reached a level comparable to natural diamond. There are two main synthetic methods: HPHT and CVD.
High temperature and high pressure (HPHT)
The method of synthesizing diamond single crystal by high temperature and high pressure method (HPHT method) is actually the temperature gradient method. This method is relatively mature, but there are some limitations. HPHT diamond particle size, purity, machinability, formability and physical and chemical properties of the adjustable and so on there is a lot of room for improvement. HPHT diamond is difficult to form a large area of film or sheet, physical and chemical properties are difficult to adjust, so its application scope is limited.
Chemical vapor deposition (CVD)
CVD synthesis of single crystal diamond is quite different from diamond polycrystalline film technology. Single crystal diamond synthesis requires the use of high-quality single crystal diamond with special requirements as the substrate, that is, this method has special requirements for the seed crystal used:
First, the seed must be single crystal diamond composed of pure {100} plane.
Second, the crystal seed must have a certain size. In principle, the size of the crystal seed can be used to grow a large single crystal.
The two methods are compared as follows:
|
comparison |
HPHT |
CVD |
|
methods |
static pressure method. |
Hot filament method, direct current nanoarc plasma method, |
|
advantage |
The technology of large single crystal less than 5mm is quite mature and can realize mass production. |
High purity, large size, can grow more than one at the same time. |
|
disadvantages
|
The product is easy to contain impurities, easy to produce defects, long growth cycle, process difficult to control, long cycle, poor reproduction rate. |
Need high quality large single crystal chip for crystal seed, equipment is expensive. |
|
product feature |
High hardness, high processing difficulty, not easy to form a large area of sheet. |
Easy to grow to large size, can exceed 15mm. |
