Topographic evolution and scaling study of ZnO (0001) single crystal after, low-energy atom beam irradiation

The topographic evaluation of the nano-scale pattern, on ZnO (001) surface, and its scaling properties have been investigated here after low energy atom beam irradiation. Preferential sputtering promotes the formation of Zn-rich zones near the surface that serve as the nucleation centers for the spontaneous nanostructure growth. The rms roughness (sigma) however increases with irradiation fluence and displays power law behaviour, sigma similar to t(beta), for t<t(c) (crossover time) but saturates at longer time scale. In the case of t>t(c), sigma is independent of irradiation time but interestingly follows the power law behaviour sigma similar to L-alpha, where L is the size of image used in analysis. The morphology of the surfaces has also been investigated using the height-height correlation and power spectral density methods. The observed values of growth (beta) and roughness (alpha) exponents indicate a scaling behavior that is induced by the disordered but well-defined geometry of the nanostructures.