Effect of the plasma composition on the structural and electronic properties of as-grown SiO _x/Si heterolayers deposited by reactive sputtering

We report the effects of varying the oxygen partial pressure (OPP) on the structural and electronic properties of SiO _x/Si heterolayers grown by RF reactive sputtering. The produced samples present silicon poly-crystalline characteristics for low values of OPP. The crystallinity decreases as the OPP increases due to oxygen interdiffusion until the silicon crystal structure becomes amorphous. The results of infrared and Raman spectroscopies show higher deviation from stoichiometry and an increment of structural disorder for samples grown with higher values of OPP. Room temperature photoluminescence (PL) is present in all as-grown samples. The PL spectra show two bands, around 1.87 and 2.16 eV, for all the samples, while a third broad band at lower energy shows up and shifts to the red as OPP increases. Our results indicate that silicon-related room temperature PL emission is correlated with the stoichiometry of the SiO _x and to the formation of silicon crystals embedded in a silicon dioxide matrix.