THE EFFECT OF THERMAL ANNEALING ON THE OPTICAL-PROPERTIES OF A-SIC-H FILMS

In this work the dependence of optical and infrared properties of Amor phous hydrogenated SiC (a-SiC:H) films on annealing temperature, T-a, is reported. The a-SiC:H films (<1 mu m thick) were RF sputtered on va rious substrates using a SiC target of constant composition. The exper imental results have shown that the optical energy band gap, E-g, of t he a-SiC thin films is nearly invariant for annealing temperatures, T- a, less than or equal to 560 degrees C, whereas in the range of T-a fr om 560 degrees C to 700 degrees C a decrease of about 0.40 eV was obse rved, and for further increase of T-a, to 775 degrees C, E-g remained invariant. A similar dependence on the annealing temperature of the sl ope of Tauc plot, B, suggests an increase of the disorder in the a-SiC :H thin films for 560 degrees C less than or equal to T-a less than or equal to 700 degrees C. The infrared measurements showed that the hyd rogen content, N-H, in a-SiC:H thin films decreases with the annealing temperature in this range, indicating the emission of hydrogen bonded to Si. This change of NH is mainly responsible for the dependence of E-g and B on T-a. Finally, the dependence of optical and infrared prop erties on T-a indicates that the RF sputtered a-SiC:H films have a bet ter thermal stability than those produced by other techniques, that ha ve so far been studied. (C) 1998 Elsevier Science B.V. All rights rese rved.