Crystalline and Electronic Structures of Ultrathin Cadmium Sulfide Films.

Herein, the crystalline and electronic structures of ultrathin cadmium sulfide {0001} films with thickness ranging from 1 to 14 Cd–S bilayers are studied using first‐principles calculations method. After structural relaxation, the film composed of 1 Cd–S bilayer is transformed into a CdS monolayer with flat honeycomb structure. Those 2‐ to 5‐bilayer films do not maintain the Wurtzite structure either: the distance between the sulfur and cadmium layers in each bilayer is compressed while the Cd–S bond length between adjacent bilayers is enlarged. These 1‐ to 5‐bilayer films reveal semiconducting characteristics in band structures, and their bandgaps are widened in some degree compared with the bulk. The films with 6–14 Cd–S bilayers keep the Wurtzite structure of the bulk, and exhibit metallic surface states due to the polarity of the films. The results could provide a new insight for the electronic structure regulation of cadmium sulfide. [ABSTRACT FROM AUTHOR]