LINEAR-DEPENDENCE OF BOTH THE HARDNESS AND THE ELASTIC-MODULUS OF PULSED-LASER DEPOSITED A-SIC FILMS UPON THEIR SI-C BOND DENSITY

Amorphous a-SiC films exhibiting excellent hardness and elastic modulu s mechanical properties, as determined by nanoindentation, have been d eposited by means of the pulsed laser deposition (PLD) technique onto either Si(100) or fused quartz substrates, at deposition temperatures ranging from 20 to 650 degrees C. The increase of the deposition tempe rature of PLD a-SiC films (from 20 to 650 degrees C) markedly enhances both their hardness and their elastic modulus. PLD a-SiC films with h ardness and elastic modulus characteristics as high as 50 and 380 GPa, respectively, are obtained at 650 degrees C deposition temperature. O n the microstructural level, the increase of the substrate deposition temperature (from 20 to 650 degrees C) favors the formation of Si-C bo nds, leading thereby to a substantial increase of the Si-C bond densit y in PLD a-SiC films, as evidenced by Fourier-transform infrared analy sis. This work clearly reinforces the concept that the Si-C bond densi ty (NSi-C) is the dominant microstructural parameter that determines t he variation of the hardness and elastic modulus of a-SiC films. Indee d, a constant-plus-linear dependence for both the hardness and the ela stic modulus of a-SiC films upon their Si-C bond density was establish ed over an NSi-C range as large as (4-24)X10(22) bond cm(-3). (C) 1997 American Institute of Physics. [S0021-8979(97)05520-5].