Chemical vapour deposition rate of Mo film in horizontal tubular reactor

A gas mixture consisting of MoCl₅, H₂ and Ar (carrier and dilute gas) was fed into an externally heated horizontal quartz tube (tubular reactor). Mo film was deposited on the inner wall of the reactor by atmospheric thermal CVD under different conditions of gas flow rate, wall (substrate) temperature and gas compositions. Film growth rate increased with the deposition temperature and the apparent activation energy was determined to be 83.5 kJ/mol in the range between 923 and 1123 K. Above 1223 K, deposits were composed of fine particles. Distribution of the film growth rate along the axial direction in the reactor was dependent on the composition of gas mixture. At high P_H2, the deposition rate was high, and a peak was formed at the inlet region in the distribution. On the other hand, a flat distribution was obtained at low P_H2. Deposition experiments were conducted using a tubular reactor with a shorter length and the output gas was condensed into powder, which was composed of MoCl₄ and MoCl₂. The fractional conversion from MoCl₅ into Mo and into the condensed powder were obtained at different gas compositions. It turned out that the effect of P_H2 change on the fractional conversion was larger than that of P_MoCl5. Considering the compounds of the deposited powder and the variation in the growth rate distribution with the gas compositions, the role of the gas phase reaction was discussed.