Formation and vibrational structure of Si nano-clusters in ZnO matrix

We have studied the formation and vibrational structure of Si nano-clusters in ZnO matrix prepared by radio-frequency (r.f.) co-sputtering, and charac terized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spec troscopy (XPS) and Infrared (IR) spectroscopy techniques. The composite fil ms of Si/ZnO were grown an quartz substrates by co-sputtering of Si and ZnO targets. TEM images demonstrated a homogeneous distribution of clusters in the matrix with average size varied from 3.7 nm to 34 nm depending on the temperature of annealing. IR absorption measurements revealed the bands cor respond to the modes of vibrations of Si-3 in its triangular geometrical st ructure. By analyzing the IR absorption and XPS spectra we found that the n ano-clusters consist of a Sis core and a SiOx cap layer. With the increase of annealing temperature, the vibrational states of Si changed from the tri plet B-3(1)(C-2v) and (3)A'(2)(D-3h) states to its singlet ground state (1) A(1)(C-2v) and the oxidation state of Si in SiOx increased. The evolution o f the local atomic structure of the Si nano-clusters with the variation of Si content in the films and with the variation of the temperature of anneal ing are discussed.