Helium Induced Structural Disorder in Hydrogenated Nanocrystalline Silicon (nc-Si:H) Thin Films Prepared by HW-CVD Method

Author(s) Nabeel A. Bakr

Department of Physics, College of Science, University of Diyala, Diyala - Iraq

Е-mail nabeelalibakr@yahoo.com
Issue Volume 4, Year 2012, Number 3
Dates Received 25 June 2012; revised manuscript received 08 July 2012; published online 29 October 2012
Citation Nabeel A. Bakr, J. Nano- Electron. Phys. 4 No 3, 03006 (2012)
PACS Number(s) 1.15.Gh, 81.07.Bc, 73.63.Bd
Key words HW-CVD, Hydrogenated Nanocrystalline Silicon (2) , Helium Dilution of Silane, Raman Spectroscopy (15) , Structural Disorder.
Structural, optical and electrical properties of hydrogenated nanocrystalline silicon (nc-Si:H) films, deposited from silane (SiH4) and helium (He) gas mixture without hydrogen by hot wire chemical vapor deposition (HW-CVD) method were investigated as a function of helium dilution of silane (RHe). We observed that the deposition rate is much higher (4-33 Å/s) compared to conventional plasma enhanced chemical vapour deposited (PE-CVD) nc-Si:H films. Raman spectroscopy revealed that the crystalline volume fraction decreases with increasing He dilution of silane whereas the crystallite size remains almost constant (~ 2 nm) for the entire range of He dilution of silane studied. Furthermore, an increase in the structural disorder in the nc-Si:H films has been observed with increasing He dilution of silane. The hydrogen content was ~ 9 at. % in the film deposited at 60 % RHe and decreases rapidly as RHe increases further. The photoresponse decreases by order of 1 with increasing helium dilution of silane from 60 to 97 %. It has been concluded that adding helium gas to the silane induces the structural disorders in the hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared by HW-CVD method.