Template-assisted electrochemical deposition of ultrathin films of cadmium sulfide

Abstract

Uniform thin films of cadmium sulfide were prepared by template-assisted electrochemical deposition on gold electrodes covered with Langmuir-Blodgett (LB) films. An electrolytic cell was used for the production of low concentrations of S − to effect heterogeneous crystallization on LB films, while preventing homogeneous precipitation. 3-, 4-, and 5-layer LB films of cadmium arachidate were investigated. Characterization of deposited films by optical microscopy, atomic force microscopy and energy dispersive X-ray analysis of film composition indicated that a variety of different types of CdS films can be produced depending on the type of LB film used, the electrode at which template-assisted deposition is carried out, the magnitude and frequency of alternating potentials used, and the deposition time used. In general, hydrophilic organic films that present cadmium carboxylate groups to the deposition surface (i.e. 3- and 5-layer LB films) supported crystallization of CdS, while those that present hydrophobic, methyl groups (i.e. 4-layer LB films and self-assembled monolayers of alkanethiolates on gold) did not. The best methods for the rapid deposition of conformal, ultrathin films (< 100 nm) of CdS used highly-ordered 5-layer LB films at grounded electrodes. The data presented suggest that templating with LB films, when used together with electrochemical deposition, has potential for the convenient production of oriented crystalline thin films of cadmium sulfide and similar materials.