Hardness and stiffness of amorphous SiCxNy chemical vapor deposited coatings

Thick amorphous SiCxNy coatings have been deposited by chemical vapor depos ition at 1000-1200 degrees C from the TMS-NH3-H-2 system. Hardness (H) and stiffness (E) were measured by nanoindentation with a Berkovich indenter. T he relative influence on H and E have been investigated using an experiment al design by varying: deposition temperature; pressure; and ammonia flow ra te. The deposits exhibit a high chemical complexity in a large domain of co mposition (0.04 less than or equal to x/x + y)less than or equal to 0.67) w ith Si(C4-nNn) units connected by sp(3)-sp(2) carbon configurations. Correl ations between the mechanical features and the chemical bonding and local o rder around the different atoms have been established. Two groups of sample s have been distinguished depending on the x/(x+y) ratio. Below x/(x+y)=0.1 , the N-rich coatings were obtained in which the main bond was Si-N and H a nd E tended to decrease from 27 to 31 GPa and 224 to 289 GPa, respectively, with increasing numbers of Si-C, C-N and C-C bonds. For 0.38 less than or equal to x/(x+y)less than or equal to 0.67, the C-rich coatings were obtain ed for which the increases of H and E from 29 to 38 GPa and 240 to 360 GPa, respectively, have been correlated to the increasing proportion of SiC4 un its. (C) 1999 Elsevier Science S.A. All rights reserved.