Thermal accommodation of a gas on a surface and heat transfer in CVD and PECVD experiments

CARS measurements of gas temperature profiles performed at low pressure (about 1 Torr) in a PECVD RF reactor and in a CVD reactor reveal the thermal accommodation phenomenon between the gas and the surfaces. A one-dimensional thermal model has been developed to calculate the temperature profiles in the PECVD and CVD reactors and the results are compared with the experimental measurements. In addition to the thermal conduction and accommodation, the model takes into account the radiative exchange between the surfaces. The influence of the pressure on the temperature jump between the gas and the surfaces was investigated in the CVD reactor. Thermal accommodation probabilities for five gas/surface couples have been determined: 0.07-0.13 for H-2/stainless steel, 0.05+/-0.01 for H-2/Si, 0.17+/-0.02 for H-2/graphite, 0.38+/-0.03 for N-2/stainless steel and 0.26+/-0.02 for N-2/graphite. In the PECVD reactor, the influence of the electrical power deposited in the plasma on the temperature profile between the electrodes was studied.