Growth kinetics of W5Si3 layer in WSi2/W system

Growth kinetics of the W 5 Si 3 layer in the WSi 2 /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 WSi 2 /0.3 μm–W 5 Si 3 /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 W 5 Si 3 layer was simultaneously formed both at the surface of the WSi 2 layer and at the interface between the WSi 2 layer and the W substrate. The W 5 Si 3 layer observed at the surface of WSi 2 layer was formed by loss of Si released from the decomposition of WSi 2 phase into the W 5 Si 3 and Si phases. The growth kinetics of W 5 Si 3 layer formed at the interface between the WSi 2 layer and the W substrate obeyed a parabolic rate law, indicating the diffusion-controlled growth. From the change of columnar diameter and texture of W 5 Si 3 grains, the dominant diffusion element and growth mechanism of the W 5 Si 3 layer was found. The integrated interdiffusion coefficients in the W 5 Si 3 phase were determined.