Synthesis And Characterization Of Nanocrystalline Si Film

Nanocrystalline Si （nc-Si）, which permits bandgap tuning, effcient room temperatureluminescence, is considered to be an outstanding candidate in photonic and microelectronicindustry. In this work, nc-Si films were fabricated by thermal treatment of sillicon rich oxide（SRO） film deposited by magnetron sputtering on Si substrate. The morphology,structure,thickness, optical properties of the nc-Si film and the multilayer of nc-Si/SiO₂filmwere characterized by transmission electron microscope （TEM）, Fourier-transform infrared（FTIR）, X-ray photoelectron spectroscopy （XPS）, and photoluminescence （PL）, respectively.1. The SRO films were deposited on Si（100） substrate by co-sputtering of Si and SiO₂.There are better quality nc-Si existing in the sample of the Si/SiO₂sputtering power ratio of4.The as-deposited SRO film is a kind of sub-stoichiometry silicon oxide, whose composition canbe tuned by the Si/SiO₂power ratio. It is demostrated that adjusting Si content is difficult totune the density and the size distribution of nc-Si.2. Silicon oxide films containing nc-Si have been fabricated by magnetron sputteringmethod followed by one-step-annealing, two-step-annealing and rapid thermal processing （RTP）,respectively. In silicon-rich oxide films containing⁴2.63at.%of Si, dense nc-Si in a magnitudeof10¹²/cm^-2were obtained in all of the samples subjected to three different thermal treatments.In the two-step-annealing sample, the density of nc-Si reachs a maximum （2.2×1012/cm-2）, andthe nc-Si are well crystallized and uniform in size distribution. In the one-step-annealing sample,the density of nc-Si is silightly lower with respect to the two-step-annealing sample, anddeficiently crystallized large nc-Si are observed in the sample. The RTP lead to the lowestdensity of nc-Si with largest size distribution among the three samples. Moreover, large nc-Siformed by coalescence of small ones by twinning have also been discovered in the RTP sample.It is considered that nucleation at the early stage of nanocrystal growth influence the density andthe micostructure of nc-Si. The annealing at low temperature in the two-step-annealing facilitatesthe formation of new nulcei, which is beneficial to improving the quality and density of nc-Si.3. In order to realize the uniform size distribution and ordered arrangements of the nc-Si, amultilayer with SRO and stoichiometric SiO₂precursor layer was fabricated and annealed at at ahigh temperature to selectively precipitate nc-Si in SRO. It was found that in multilayernc-Si/SiO₂film the ultimate size of the nc-Si can be determined by the thickness of the SiO₂layer.