Structural and optical properties of a-Si1−xCx:H grown by plasma enhanced CVD

In this work, we discuss on the physical properties of hydrogenated amorphous silicon carbide (a-Si1−xCx:H) thin films deposited by plasma enhanced CVD by using SiH4+CH4 and SiH4+C2H2 gas mixtures under several deposition conditions. We can argue a complete chemical order in the samples deposited by SiH4+CH4 for x>0.4, while for those grown by SiH4+C2H2, such order is preserved for lower C content. With regards to the radiative properties, for all the under-stoichiometric samples the photoluminescence (PL) Stokes shifts result to be strictly correlated to the absorption properties within the static disorder model. For C-rich materials, the electronic density of states becomes much more complex than in Si-rich ones because of the possibility of sp2 and sp3 configurations for C bonds, so that the presence of localized tail states cannot explain anymore the PL properties.