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Spectroscopic detection of medium range order in device quality hydrogenated amorphous silicon, a-Si(H)

G. LUCOVSKY1,* , G. PARSONS1, D. ZELLER1, K. WU1, B. PAPAS1, J. WHITTEN1, R. LUJAN2, R. A. STREET2

Affiliation

  1. North Carolina State University Raleigh, N.C., 27695-8202, USA
  2. The Palo Alto Research Company, a Xerox Company, Palo Alto, CA, 94303, USA

Abstract

Hydrogenated amorphous silicon, a-Si1-xHx, x ~0.1±0.02, has been used extensively in photo-voltaics and thin film transistors. This alloy has been deposited by the glow discharge method, remote plasma-enhanced chemical vapor deposition, and reactive magnetron sputtering with varying amounts of bonded-H determined by deposition precursors and substrate temperatures. Two conditions are required for ultra-low Si dangling bond densities of order 0.5 to 1x1016 cm-3: (i) a bonded monohydride, Si-H, concentration with 8 to 12 at.% H, and (ii) a deposition, and/or a post-deposition anneal at ~240 to 300°C. These conditions promote diffusion of H resulting in an optimized redistribution that reduces strain macroscopically, creating low Si dangling bond densities. Second derivative Si L2,3 X-ray absorption spectroscopy has been used to confirm medium (or intermediate) range order extending beyond the short range order of continuous random networks through the observation of ligand field split features. These are associated with symmetry-adapted linear combinations of atomic states forming molecular orbital valence band states extending to at least 3rd Si neighbors. Medium range order can also be identified by complementary spectroscopic techniques, such as spectroscopic ellipsomentry (SE), and ultra-violet or X-ray photoemission spectroscopy (UPS or XPS)..

Keywords

a-Si, H, Spectroscopic detection, Medium range order.

Submitted at: Nov. 1, 2011
Accepted at: Nov. 23, 2011

Citation

G. LUCOVSKY, G. PARSONS, D. ZELLER, K. WU, B. PAPAS, J. WHITTEN, R. LUJAN, R. A. STREET, Spectroscopic detection of medium range order in device quality hydrogenated amorphous silicon, a-Si(H), Journal of Optoelectronics and Advanced Materials Vol. 13, Iss. 11-12, pp. 1586-1589 (2011)