1. Temperature:
o Reaction temperature: A higher reaction temperature can increase the energy of the raw gas molecules, promote the activation of the reactant molecules, accelerate the reaction rate, and thus increase the growth rate of the seed crystals. However, too high or too low a temperature may cause the reaction to tend to thermodynamic equilibrium, which is not conducive to increasing the growth rate.
o Substrate temperature: A suitable substrate temperature gradient can regulate the growth rate and film structure, and also has an important influence on heat conduction and adsorption of reactants.
2. Raw gas:
o Concentration: Increasing the raw gas concentration usually increases the deposition rate, thereby accelerating the growth of the seed crystals. However, too high a concentration may lead to instability and the formation of by-products, which in turn affects the growth rate and quality.
o Ratio: Different raw gas ratios will affect the reaction kinetics. An appropriate ratio can promote rapid and uniform deposition, which is conducive to the growth of seed crystals.
3. Gas phase mass transfer:
o Gas phase diffusion: Gas phase mass transfer is affected by the gas flow conditions in the reaction chamber and the surface morphology of the substrate. Effective gas phase mass transfer can ensure that the reactants are evenly transported to the reaction surface, thereby improving the growth rate and uniformity. If the gas phase mass transfer is not smooth, it will lead to insufficient supply of reactants and limit the growth of seed crystals.
o Substrate surface morphology: The flatness, roughness and other morphological characteristics of the substrate surface will affect the gas phase mass transfer. A flat and smooth surface is conducive to the uniform adsorption and deposition of reactants, while a rough surface may cause turbulent airflow, affecting the growth rate and uniformity.
4. Reaction material selection 2: Different reactants have different reactivity and volatility. Highly reactive substances can accelerate the reaction rate and are conducive to seed crystal growth; highly volatile reactants are conducive to uniform deposition and rapid film formation, thereby increasing the growth rate.
5. Pressure: In the CVD process, pressure has an impact on plasma density. Properly increasing the pressure can increase the plasma density, which helps to increase the concentration of active groups such as atomic H and methyl CH₃, thereby accelerating the growth rate of seed crystals.
6. Power: For technologies such as microwave plasma CVD, increasing the power can enhance the energy of the plasma, so that the raw gas can be more fully dissociated and excited, produce more active particles, and promote seed crystal growth.
7. Doping: Nitrogen doping at a certain ratio can significantly increase the growth rate of diamond seeds, but as the nitrogen addition ratio increases, the growth rate gradually tends to saturation. In addition, the doping of some other impurities or elements may also affect the growth rate of the seeds.
8. Magnetic field: The external magnetic field may affect the properties and behavior of the material, and thus affect the growth rate and morphology of the seeds. However, the effect of the magnetic field on the growth rate of CVD seeds is more complicated, and the specific effect varies depending on the material system and experimental conditions.
