DEPENDENCE OF OPTICAL AND ELECTRICAL-PROPERTIES OF A-SI1-XCX-H FILMS ON THERMAL ANNEALING

In this study, the a-Si1-xCx:H film prepared by the glow discharge met hod is examined after thermal annealing in the temperature range of 25 0 degrees C to 800 degrees C. The relation between the change of the b onding state among the component elements of the film and the optical/ electrical properties of the film is investigated by analysis of the u ltraviolet and infrared absorption spectrum, as well as the X-ray phot oelectron spectrum. It is seen that by raising the thermal annealing t emperature of the sample film, hydrogen evolution starts around 350 de grees C, and the bonding state of Si, C, and H is accordingly greatly reconfigurated. C-H, (n = 1, 2, 3) and Si-C bonds reach a maximum and minimum, respectively, at an annealing temperature of approx. 500 degr ees C to 600 degrees C. This temperature is found to agree with the te mperature at which the dark conductivity starts to increase. It is als o found that the above temperature tends to decrease with increasing c arbon content of the film. The optical band gap of the film strongly d epends on the C-n-Si-H (n = 1, 2, 3) bonding units, for which the stre tching mode absorption spectrum is 2000 cm(-1) to 2200 cm(-1). It is c onjectured that the increase of the optical band gap, due to the incre asing carbon content of the film, is related to the amount of carbon c ombined in the bonding units. (C) 1997 Scripta Technica, Inc.