Influence of Formation Conditions on Structure and Properties of Paramagnetic Centers in Polymorphous Silicon Films

Abstract

Paramagnetic properties of two series of polymorphous silicon thin films deposited by plasma-enhanced chemical vapor deposition with variation of silane and hydrogen gas mixture pressure and substrate temperature have been studied by means of electron paramagnetic resonance (EPR) spectroscopy. For the first time EPR signal with g-tensor values g₁ = 1.9984, g₂ = 1.9890, g₃ = 1.9790 was detected in the polymorphous silicon structure. We have attributed this signal to the electrons trapped in conduction band tail states at the interface between nanocrystals and/or at the grain boundaries between silicon nanocrystals. An activation energy of electron transition from band tail states to the conduction band was estimated approximately to 40 meV. Observed changes of the paramagnetic center concentration vs substrate temperature and gas pressure in the reaction chamber during polymorphous silicon film preparation are discussed.