Nanostructured metal sulfide surfaces by ion exchange processes

A scalable preparation procedure for structured semiconducting sulfide films from zinc oxide by means of subsequent anion and cation exchange processes is described, which is low in cost and waste production. The starting material was columnar ZnO films, which were grown in electrodeposition by O-2 reduction. Here, their detailed morphology depends on the substrate and the process parameters. These films were converted to ZnS by reaction with H2S gas or sulfur vapour at temperatures around 450 degreesC. In this process the columnar morphology of the ZnO is preserved. A partial conversion is also possible and leads to tubular ZnS films. Then the ZnS films were reacted in metal salt solutions to convert them further to Ag2S, Cu2S, Bi2S3 and Sb2S3 films. Here the columnar or tubular morphology was, in general, also reproduced, but its outer quality depends on the interaction of the involved processes, namely dissolution, precipitation and exchange inside the solid. This was further examined by a series of Ag2S films from modified solutions.