Depth-dependent crystallinity of nano-crystalline silicon induced by step-wise variation of hydrogen dilution during hot-wire CVD

6th International Conference on Optical, Optoelectronic and Photonic Materials and Applications 2014

Arendse, C.J.^1 ; Van Heerden, B.A.^1 ; Muller, T.F.G.^1 ; Cummings, F.R.^1 ; Oliphant, C.J.^2 ; Malgas, G.F.^1 ; Motaung, D.E.^3

Department of Physics, University of the Western Cape, Private Bag X17, Bellville

7535, South Africa^1

National Metrology Institute of South Africa, Private Bag X34, Lynnwood Ridge, Pretoria

0004, South Africa^2

DST/CSIR National Centre for Nano-Structured Materials, P. O. Box 395, Pretoria

0001, South Africa^3

关键词: Amorphous surface layers;    Amorphous surfaces;    Chemical vapour deposition;    Effective Medium Approximation;    Film/substrate interface;    Fixed time interval;    Oxygen bonding configurations;    Transmission spectroscopy;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/619/1/012002/pdf
DOI  :  10.1088/1742-6596/619/1/012002

来源: IOP

【 摘 要 】

To induce an amorphous surface in a nano-crystalline silicon (nc-Si:H) thin film, the hydrogen dilution was reduced step-wise at fixed time intervals from 90 - 50% during the hotwire chemical vapour deposition process. This contribution reports on the structural properties of the resultant nc-Si:H thin film as a function of the deposition time. Raman spectroscopy, confirmed by high resolution transmission spectroscopy, indicates crystalline uniformity in the growth direction, accompanied by the progression of an amorphous surface layer as the deposition time is increased. The silicon- and oxygen bonding configurations were probed using infrared spectroscopy and electron energy loss spectroscopy. The growth mechanism is ascribed to the improved etching rate by atomic hydrogen in nano-crystalline silicon towards the film/substrate interface region. The optical properties were calculated by applying the effective medium approximation theory, where the existence of bulk and interfacial layers, as inferred from cross-sectional microscopy, were taken into account.