Photoconducting a-Si:H films grown at high deposition rates by pulsing a VHF 100 MHz discharge

Mukherjee, C and Anandan, C and Seth, T and Dixit, PN and Bhattacharyya, R (2003) Photoconducting a-Si:H films grown at high deposition rates by pulsing a VHF 100 MHz discharge. Thin Solid Films, 423 (1). pp. 18-26.

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Abstract

In a novel experiment hydrogenated amorphous silicon films were deposited by modulating the very high frequency (VHF) (100 MHz) discharges, at low frequency (2 Hz) with a nonzero low power level, using pure as well as 25% hydrogen and 25% helium diluted silane as the source gases. During these studies deposition rate is found to depend on the dwell time as in the case of RF pulsed plasma CVD reported earlier by the authors. The films were characterised for optical bandgap, dark and photoconductivity, hydrogen content, microstructure factor, Urbach energy and defect density. The results indicate that, unlike the RF pulsed plasma case, there is an order of magnitude improvement in the photoconductivity of the material due to pulsing the VHF discharges. Urbach energy and defect density studies also indicate an improvement in the film quality. The improvements are more pronounced in diluted silane deposited films. Controlled ion bombardment (of high flux and lower energy) and the resulting ion bombardment induced preparation of the growth surface in the VHF discharges are believed to be the main factors contributing to the observed results. Thus, a more favourable sheath characteristics as obtained during pulsed VHF discharge conditions over RF (13.56 MHz). Silane discharges holds the key to obtain high growth rate deposition of a-Si:H films of acceptable opto-electronic quality xA9; 2002 Elsevier Science B.V. All rights reserved.

Item Type: Journal Article
Uncontrolled Keywords: Amorphous silicon; Chemical vapour deposition; High deposition rate; Photoconductivity; Pulse plasma CVD; Amorphous silicon; Ion bombardment; Microstructure; Photoconducting materials; Photoconductivity; Plasma enhanced chemical vapor deposition; Very high frequency (VHF); Film growth;
Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Division/Department: Other, Surface Engineering Division, Other, Other, Other
Depositing User: MS Jayashree S
Date Deposited: 07 Jan 2005
Last Modified: 24 May 2010 09:38
URI: http://nal-ir.nal.res.in/id/eprint/58

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