Microstructure and growth kinetics of the Mo5Si3 and Mo3Si layers in MoSi2/Mo diffusion couple

The microstructures and growth kinetics of the Mo5Si3 and Mo3Si layers in the MoSi2/Mo diffusion couple was investigated using optical microscopy, field-emission scanning electron microscopy, electron probe microanalyzer, and cross-sectional transmission electron microscopy. The MoSi2/Mo diffusion couple was made by chemical vapor deposition CVD of Si on a Mo substrate at 1100 °C and annealed at temperatures between 1250 and 1600 °C in an Ar atmosphere. Simultaneous parabolic growth of the Mo5Si3 and Mo3Si layers was observed at the early annealing stage of the MoSi2/Mo diffusion couple. From the marker experiments using ZrO2 particles, the growth mechanism of the Mo5Si3 and Mo3Si layers and the dominant diffusion element in each phase were revealed. The difference in the growth rates of Mo3Si layer between the MoSi2/Mo diffusion couple and the Mo5Si3/Mo diffusion couple was explained by a multiple layer growth model.