Controlling the preferred orientation in sputter-deposited Cu2O thin films: Influence of the initial growth stage and homoepitaxial growth mechanism
Résumé
We report the homoepitaxial growth of Cu2O thin films with tunable growth orientations on glass and silicon substrates using reactive sputtering. The importance of the initial growth stage on the subsequent development of specific orientations is detailed. Among the various deposition conditions, the total pressure is found to have a strong effect on the preferred orientation of Cu2O films: (1 0 0) at low pressure and (1 1 1) at high pressure. Furthermore, the texture of the deposited films is also influenced by that of a first Cu2O layer acting as a continuous seed layer. Effectively, using a two-step deposition procedure, a highly textured Cu2O thin film with controlled orientation can be formed independently of the deposition conditions. Provided that it has a sufficient thickness, this layer acts as a seed layer that determines the crystal orientation of a second layer grown even after air exposure and/or without specific cleaning of the surface prior to deposition. High-resolution transmission electron microscopy analyses evidence that the top layer grows in homoepitaxy with the seed layer with a microstructure consisting of single crystal columns crossing the interface between the layers.