Surface roughening transition in Si1-xGex:H thin films

Nikolas J. Podraza, Christopher R. Wronski, Mark W. Horn, Robert W. Collins

Research output: Chapter in Book/Report/Conference proceedingConference contribution


In this study, the amorphous-phase roughening transition thickness has been determined as a function of process variables in plasma-enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon-germanium alloys (a-Si1-xGex:H). Among the process parameters varied include the H2-dilution gas flow ratio, the alloying flow ratio, the electrode configuration (anode vs. cathode), and the He-dilution ratio. One clear feature of this study is a maximum in the amorphous roughening transition thickness (and hence surface stability) at a H2-dilution ratio just below the transition from amorphous to mixed-phase (amorphous+ microcrystalline) (a+μc) growth. A second feature for high Ge content films is a significant increase in the roughening transition thickness for cathode PECVD (with a self-bias of ∼ -20 V) relative to anode PECVD. Additional features of interest involve suppression of the transition to (a+μc) for (i) alloying with Ge, (ii) biasing the substrate cathodic, and (iii) diluting the gas with He. The close correlation of high surface stability with enhanced short-range order and overall electronic performance has led to a simple model for the transition in terms of a competition between roughening due to the atomic size and smoothening due to precursor surface diffusion. It is proposed that diffusing precursors are immobilized by surface defects (or by other diffusing precursors), and the pre-existing (or resulting) defects are ultimately incorporated in the bulk.

Original languageEnglish (US)
Title of host publicationAmorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2006
Number of pages6
StatePublished - 2007
Event2006 MRS Spring Meeting - San Francisco, CA, United States
Duration: Apr 18 2006Apr 21 2006

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2006 MRS Spring Meeting
Country/TerritoryUnited States
CitySan Francisco, CA

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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