Raman study of thin films of amorphous-to-microcrystalline silicon prepared by hot-wire chemical vapor deposition

The structure changes of thin films of amorphous (a) to microcrystalline (μc) silicon are studied by Raman scattering in terms of three deposition parameters: the silane flow rate, the hydrogen flow rate, and the total gas pressure in hot-wire chemical vapor deposition. The Raman transverse optical (TO) mode is deconvoluted into two Gaussian functions for a-Si:H and intermediate components and one Lorenzian function for the c-Si component. We found that (a) in general, the change in structure is a function of the ratio of hydrogen to silane gas flow, R, but also depends on the SiH4 flow rate and total gas pressure; (b) there is a narrow structural transition region in which the short-range order of the a-Si:H network improves, i.e., the variation in bond angle of the a-Si network decreases from ∼10° to ∼8° once the c-Si grains start to grow; and (c) when the films were deposited using a high SiH4 flow rate of 22 sccm, the narrow TO mode with low peak frequency could be related to the column-like structures.

[1]  F. Finger,et al.  Structure and growth of hydrogenated microcrystalline silicon : investigation by transmission electron microscopy and Raman spectroscopy of films grown at different plasma excitation frequencies , 1997 .

[2]  Zafar Iqbal,et al.  A thermodynamic criterion of the crystalline-to-amorphous transition in silicon , 1982 .

[3]  Veprek,et al.  Effect of grain boundaries on the Raman spectra, optical absorption, and elastic light scattering in nanometer-sized crystalline silicon. , 1987, Physical review. B, Condensed matter.

[4]  S. Ovshinsky,et al.  Heterogeneity in hydrogenated silicon: Evidence for intermediately ordered chainlike objects , 2001 .

[5]  Ch. Hof,et al.  On the Way towards High-Efficiency Thin Film Silicon Solar Cells by the "Micromorph" Concept , 1996 .

[6]  S. Guha,et al.  Electronic states of intrinsic layers in n-i-p solar cells near amorphous to microcrystalline silicon transition studied by photoluminescence spectroscopy , 2000 .

[7]  Gerard T. Barkema,et al.  Raman spectra and structure of amorphous Si , 2001 .

[8]  Qi Wang,et al.  A combinatorial study of materials in transition from amorphous to microcrystalline silicon , 1999 .

[9]  Reinhard Carius,et al.  Structural properties of microcrystalline silicon in the transition from highly crystalline to amorphous growth , 1998 .

[10]  Liyou Yang,et al.  RECOMBINATION AND METASTABILITY IN AMORPHOUS SILICON P-I-N SOLAR CELLS MADE WITH AND WITHOUT HYDROGEN DILUTION STUDIED BY ELECTROLUMINESCENCE , 1996 .

[11]  J. Dongun Kim,et al.  High‐resolution transmission electron microscopy study of solid phase crystallized silicon thin films on SiO2: Crystal growth and defects formation , 1995 .

[12]  Beeman,et al.  Structural information from the Raman spectrum of amorphous silicon. , 1985, Physical review. B, Condensed matter.

[13]  Hitoe Habuchi,et al.  Hydrogen structures and the optoelectronic properties in transition films from amorphous to microcrystalline silicon prepared by hot-wire chemical vapor deposition , 2003 .

[14]  É. Bustarret,et al.  Experimental determination of the nanocrystalline volume fraction in silicon thin films from Raman spectroscopy , 1988 .

[15]  Qi Wang,et al.  Photoluminescence and Raman studies in thin-film materials: Transition from amorphous to microcrystalline silicon , 1999 .

[16]  Yuliang He,et al.  The structure and properties of nanosize crystalline silicon films , 1994 .

[17]  S. Guha,et al.  Structural, defect, and device behavior of hydrogenated amorphous Si near and above the onset of microcrystallinity , 1999 .

[18]  L. Gedvilas,et al.  Structural properties of hot wire a-Si:H films deposited at rates in excess of 100 /s , 2001 .