Asymmetric growth on the polar surfaces of CdS ribbons

Cadmium sulfur ribbons were produced on an Au-coated Si substrate by chemical vapor deposition of CdS powder. The growth direction of the ribbons was [ 0 1 1 ¯ 0 ] . Asymmetric growth had occurred on the ±(0 0 0 1) planes. Two types of ribbons were found. In one type, saw-tooth structure was rooted on the active Cd-terminated (0 0 0 1) surface while the inert S-terminated ( 0 0 0 1 ¯ ) surface remained flat. In the second type, finer finger/saw-tooth pairs were found on one side, nano-finger-like structure was on the other. The nano-fingers were grown on some high-energy planes between the S-terminated ( 0 0 0 1 ¯ ) plane and the ± ( 2 1 ¯ 1 ¯ 0 ) facets. This lateral asymmetric growth behavior was due to surface polarization.