Nano Express

Nanoscale Research Letters

, 4:307

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Thermally Induced Nano-Structural and Optical Changes of nc-Si:H Deposited by Hot-Wire CVD

  • CJ ArendseAffiliated withCSIR National Centre for Nano-Structured MaterialsDepartment of Physics, University of the Western Cape Email author 
  • , GF MalgasAffiliated withCSIR National Centre for Nano-Structured Materials Email author 
  • , TFG MullerAffiliated withDepartment of Physics, University of the Western Cape
  • , D KnoesenAffiliated withDepartment of Physics, University of the Western Cape
  • , CJ OliphantAffiliated withCSIR National Centre for Nano-Structured MaterialsDepartment of Physics, University of the Western Cape
  • , DE MotaungAffiliated withCSIR National Centre for Nano-Structured MaterialsDepartment of Physics, University of the Western Cape
  • , S HalindintwaliAffiliated withDepartment of Physics, University of the Western Cape
  • , BW MwakikungaAffiliated withCSIR National Centre for Nano-Structured MaterialsSchool of Physics, University of the WitwatersrandDepartment of Physics, University of Malawi, The Polytechnic

Abstract

We report on the thermally induced changes of the nano-structural and optical properties of hydrogenated nanocrystalline silicon in the temperature range 200–700 °C. The as-deposited sample has a high crystalline volume fraction of 53% with an average crystallite size of ~3.9 nm, where 66% of the total hydrogen is bonded as ≡Si–H monohydrides on the nano-crystallite surface. A growth in the native crystallite size and crystalline volume fraction occurs at annealing temperatures ≥400 °C, where hydrogen is initially removed from the crystallite grain boundaries followed by its removal from the amorphous network. The nucleation of smaller nano-crystallites at higher temperatures accounts for the enhanced porous structure and the increase in the optical band gap and average gap.

Keywords

Hot-wire CVD Quantum size effects Nano-crystallite Optical band gap