Advantages
1. Large-size and high-quality crystals: High temperature and high pressure method (HPHT) can induce rapid rearrangement and crystallization of carbon atoms under the extreme conditions of high temperature (about 1500℃) and high pressure (5 - 6GPa), and can grow large-size and high-quality diamond monocrystalline slices. With fewer defects and better crystallization integrity, the output crystals have obvious advantages in high-end applications, such as precision optical components and heat sinks for high-power electronic devices, and can meet the strict requirements on material properties and dimensions.
2. Relatively mature process system: After a long period of development, the process of preparing diamond single crystal flakes by HPHT method has been relatively mature, with high technical stability. From raw material selection, equipment operation to process parameter regulation, there are more perfect standards and processes, which makes the production process relatively easy to control, product quality consistency is better, and is conducive to industrialized large-scale production.
3. High growth rate: Compared with the partial chemical vapor deposition (CVD) method, HPHT method has a faster growth rate. Under appropriate pressure and temperature conditions, it can obtain a certain thickness of diamond monocrystalline wafers in a relatively short time, effectively improving production efficiency and reducing time costs, which is more suitable for large-scale production scenarios with high requirements on production efficiency.
Disadvantages
1. Expensive equipment and high operating costs: the realization of high temperature and high pressure environment requires specialized large-scale equipment, such as six-sided top presses, etc., the acquisition cost of equipment is extremely high. At the same time, the equipment operation process needs to consume a lot of energy to maintain the high temperature and high pressure state, routine maintenance also requires specialized technical personnel and high costs, which makes the overall production cost increased significantly, limiting the application of the method in some cost-sensitive areas.
2. Stringent process conditions: HPHT is extremely demanding in terms of process conditions. Small deviations in temperature, pressure, reaction time and other parameters may lead to crystal growth failures or quality degradation. For example, pressure fluctuation may cause stress defects inside the crystal, and improper temperature control may cause uneven crystal growth, which requires very high technical level and experience of the operators, and increases the difficulty and uncertainty of production.
3. Raw material limitation and environmental pollution: usually graphite is used as raw material to synthesize diamond under the action of catalyst. However, the purity of graphite raw material is very high, and the resources of high-quality graphite are limited. In addition, some catalysts are difficult to be recycled after the reaction, which may cause pollution to the environment. Moreover, the high-temperature and high-pressure exhaust gas generated in the production process will also have adverse effects on the environment if not handled properly, which is a challenge at a time when environmental protection requirements are becoming increasingly stringent.
4. Limitations of substrate selection: Due to the high temperature and high pressure environment of the HPHT method, the choice of substrate materials is limited. Ordinary materials are difficult to withstand such extreme conditions, and the special substrate materials that can be adapted are often expensive, which not only increases the cost, but also limits the use of different substrate properties, which is not conducive to customizing the performance of diamond single crystal wafers according to specific needs.
