Microstructure of Sn_(1-x)Pb_x S grown by hot-wall technique

摘要

Orthorhombic Sn_(1-x)Pb_xS (x≈0.1) was grown on glass substrates by hot-wall technique. The entire deposited material is subdivided into a more or less continuous layer and whiskers grown on it. The former one consists of stacked blocks with their c-axis always parallel to growth direction. However, each block is alternately rotated 90° around the [001] against its underlying and following one. Therefore, the boundaries between them are twist boundaries having an orthogonal network of pure screw dislocations due to plastic relaxation. On these blocks Sn_(1-x)Pb_xS whiskers of the same composition grow via a VLS mechanism. Especially, these whiskers consist of either thicker misaligned blocks, too (at 300℃), or at higher growth temperatures (e.g., 320℃) they contain many 90°-twisted very thin strained sequences being intergrown pseudomorphically. Based on α-SnS (Herzenbergite) a structural model is presented which is sufficient to describe the defects observed and to simulate the corresponding HRTEM images.