Infrared absorption and evidence of Si3 nanocluster formation in Si/ZnO composites

Si nanoclusters embedded in ZnO matrix were prepared by radio-frequency co-sputtering and subsequent annealing of the composite films. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy techniques were used to characterize the composite films. The average size of the nanoclusters, depending on annealing temperature varied from 3.7 to 34 nm. The nanoclusters in the composites consist of a Si core surrounded by a SiOx cap layer. The Si-3 in the clusters remain mainly in its triangular geometrical structure. With the increase of annealing temperature, the vibrational state of Si-3 changes from its excited B-3(1)(C-2v) and (3)A(2)'(D-3h) triplet states to (1)A(1)(C-2v) Singlet ground state and the oxidation state of Si in SiOx cap layer increases. (C) 1999 Elsevier Science Ltd. All rights reserved.