CATHODIC AND ANODIC GLOW-DISCHARGE SILICON-CARBON ALLOYS (A-SI1-XCX-H) FROM X=0.5 TO 1 - A COMPARATIVE-STUDY BY PHOTOEMISSION (UPS) AND PHOTOLUMINESCENCE (PL)

Photoluminescence (PL) and ultraviolet photoelectron spectroscopy are used to study glow discharge amorphous silicon carbon alloys (a-Si1-xC x:H, 1 < x < 0.5) under different substrate biases. The samples were d eposited simultaneously on substrates located at the cathode and the a node. The deposition conditions were those used to produce hard a-C:H ('diamond like'). In cathodic samples, ion bombardment enhances C sp(2 ) bonds while in anodic samples the top of valence band is depressed. Both ion bombardment (negative bias) and electron bombardment (positiv e bias) decrease the PL efficiency.