Paramagnetic Defects and Photoluminescence in Carbon Rich a-SiC:H Films: Role of Hydrogen and Excess of Carbon

Abstract

AbstractThe effect of excess of carbon in a-Si1−xCx:H has been studied with regard to local structure reconstruction, evolution of paramagnetic defects and photoluminescence (PL) after vacuum annealing over the temperature range 300–850°C. Two series of samples with stoichiometric (Si0.5C0.5) and carbon-rich (Si0.3C0.7) compositions were studied by Electron Paramagnetic Resonance (EPR), Photoluminescence (PL) and Raman scattering. It is found that there exist two effects responsible for the PL efficiency of a-Si1-xCx:H films: “killing” effect of carbon-related paramagnetic defects and “enhancing” effect of carbon-hydrogen bonds in Si:C-Hn configuration. A microstructure model is proposed for explaining the non-monotonic behavior of integrated PL intensity and concentration of paramagnetic centers and Si:C-Hn bonds as a function of annealing temperature. This model evolves from the following principal processes during thermal treatment of a-Si1−xCx:H: thermally activated release of weakly bonded hydrogen, migration of hydrogen within material and interaction of hydrogen with carbon-related defects.