Magnetron sputtered nanocomposite films of SI nanocrystals embedded in SIO2 for electronic and optoelectronic applications.

Nanocomposite thin films of Si nanocrystals (nc-Si) embedded in SiO2 have attracted intensive research for potential applications in next generation non-volatile memory device as well as Si-compatible light-emitting devices. This dissertation studies the structural, electrical and optoelectronic properties of the Si nanocomposite films. The Si nanocomposite films are synthesized by reactive radio frequency magnetron sputtering of a Si target in a gas mixture of Ar/O2 followed by rapid thermal annealing at high temperatures. The synthesized films have been characterized with transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), current-voltage (I-V), capacitance-voltage (C-V) and electroluminescence (EL). The as-sputtered SiOx films are amorphous. XPS analysis reveals that the as-deposited SiOx films contain five Si chemical states (Sin+, where n = 0, 1, 2, 3 and 4) in a wide composition range. Amorphous Si nanoclusters are formed in the as-deposited SiOx films, and they are embedded in the SiO2 matrix. The physical origin of the formation of the amorphous Si clusters is the high kinetic energy of the sputtered Si atoms coupled with high surface diffusivity. An atomic model has been proposed to depict the atomic structure of the amorphous SiOx films where Si nanocluster cores are encapsulated by shell of Si suboxides, which themselves embedded in the SiO2 matrix. Si nanocrystals are formed by rapid thermal annealing the as-deposited SiOx films at elevated temperatures. The growth mechanism of nc-Si is found to be different from the classical nucleation and diffusion growth model. It is believed that thermal segregation of the Si suboxides provides rapid growth of Si nanoclusters, thus is considered the responsible mechanism.DOCTOR OF PHILOSOPHY (MAE