Vapor phase epitaxy of monocrystal tungsten coatings

Monocrystal tungsten coatings were obtained by vapor phase epitaxy in a W-WClx-Cl system using Mo single crystal substrate. The kinetics of the deposition process was studied in a wider temperature and pressure range. As the total pressure was 15.77 Pa, the surface kinetics controlled by the deposition process as the temperature was in the range of 1383-1503 K. When the deposition temperature was increased up to 1573 K, the control mechanism was mass transport limited. When the deposition temperature was maintained at 1673 K and the total pressure was 15.77-25.23 Pa, the deposition process was mass transport limited. When the total pressure was increased to 42.32 Pa, the control mechanism of the deposition process became surface kinetics limited. By basic treatment, namely, 'supply transport medium as required', a kinetics model predicting the tungsten coating growth rate was achieved. In the case of lower pressure for the surface kinetics limited regime, the deposition rate was proportional to pressure. When the pressure was high, the deposition rate was proportional to the half power of pressure. As the pressure increased further, the deposition rate and pressure became kinetically irrelevant. The model predictions were in good agreement with the experimental growth rates, as further proven by the surface morphology analysis of the monocrystal tungsten coatings.