Optical and mechanical properties of a compact ZnO layer with embedded GaP nanowires

A new type of composite antireflection coating based on a compact GaP NW/ZnO layer structure is presented. The structure was prepared by a combination of Metal Organic Vapour Phase Epitaxy (MOVPE) with RF sputtering. The former was used to grow GaP nanowires and the latter to deposit ZnO nanograins on them. The nanowires were completely engulfed by a compact ZnO layer without voids. This was achieved with a carefully optimised technique that alternated ZnO deposition and ZnO etching by argon ions. The compact structure showed a significant decrease in reflectance compared with reflectance at the GaP substrate or at the GaP substrate with the GaP NWs. Nanoindentation measurements indicated that the micro-hardness of such a compact GaP NW/ZnO layer structure was better than that of the pure ZnO layer. The structure also exhibited some degree of pseudoelasticity.