Bonding at the CdSe/SiOx (x = 0, 1, 2) interfaces

The chemistry occurring at the CdSe/Si, CdSe/SiO2 and CdSe/SiO2 interfaces was investigated by looking at very thin tapered films (0-10 nm) of thermal ly evaporated CdSe with x-ray photoelectron spectroscopy. The analysis of t he attenuation of the x-ray photoelectron signals along the tapered film wa s used to measure the electron mean free paths in as-deposited CdSe. The el ectron mean free path was found to increase with the photoelectron energy f rom 1.5 nm at 720 eV to 2.3 nm at 1200 eV. Our data suggest an island growt h mechanism for CdSe on the Si substrate and a more uniform growth on silic on oxide. In the early growth, Se is first adsorbed on the surface creating sites where Cd subsequently adsorbs. Interdiffusion is observed for CdSe o n the Si and SiO substrates after a vacuum anneal at 390 degrees C. The mai n result of this interdiffusion process is the formation of Si-Se bonds. Si milar interdiffusion processes on thermal SiO2 substrates are expected but were too small to be detected. [S0021-8979(98)02321-4].