Growth kinetics of W5Si3 layer in WSi2/W system

Growth kinetics of the W5Si3 layer in the WSi2/W diffusion couple was investigated using optical microscopy, field-emission scanning electron microscopy, cross-sectional transmission electron microscopy, and X-ray diffraction. The 62 μm WSi2/0.3 μm–W5Si3/W diffusion couple was made by chemical vapor deposition (CVD) of Si on a W substrate. When the diffusion couple was annealed at temperatures between 1300 and 1500 °C in an argon atmosphere, the W5Si3 layer was simultaneously formed both at the surface of the WSi2 layer and at the interface between the WSi2 layer and the W substrate. The W5Si3 layer observed at the surface of WSi2 layer was formed by loss of Si released from the decomposition of WSi2 phase into the W5Si3 and Si phases. The growth kinetics of W5Si3 layer formed at the interface between the WSi2 layer and the W substrate obeyed a parabolic rate law, indicating the diffusion-controlled growth. From the change of columnar diameter and texture of W5Si3 grains, the dominant diffusion element and growth mechanism of the W5Si3 layer was found. The integrated interdiffusion coefficients in the W5Si3 phase were determined.