OPTICAL AND STRUCTURAL-PROPERTIES OF HYDROGEN IMPLANTED SILICON-CARBON ALLOYS

The hydrogen effects on the optical and structural properties of amorp hous silicon carbon alloys are investigated for different hydrogen con centration (0-20 at.%) and a fixed silicon to carbon concentration rat io (x(Si)/x(C) = 1). Hydrogen was introduced into a preamorphized SiC sample by ion implantation of H ions with energies in the range 5-20 k eV and fluences in the range 10(17)-5 X 10(17) ions/cm(2) obtaining an uniform concentration in the amorphous layer (130 nm thick). Raman sp ectra evidences the presence of both a-Si and a-C structures even in t he unhydrogenated samples and the optical energy gap increases with hy drogen concentration. Thermal annealing at 350 degrees C induces a fur ther increase of the optical energy gap, in particular from 1.45 to 1. 65 eV in the 20 at.% hydrogen containing a-SiC:H. These and other resu lts, compared to those obtained in pure amorphous silicon and carbon l ayers, suggest a similarity between the optical and structural behavio ur of silicon carbon alloys and that of amorphous carbon.