Enhanced hardness in two-layer a-BON/nc-SiC coating prepared by plasma-assisted MOCVD and thermal MOCVD

We have synthesized the simple a-BON and nc-SiC thin films as well as multilayered a-BON/nc-SiC thin film on Si(001) substrates by combining low-frequency RF-derived plasma-assisted MOCVD and thermal MOCVD in the deposition temperature range of 300-900 °C trimethylborate (TMB), and diethylmethylsilane (DEMS) precursors were used to grow a-BON and nc-SiC thin films, respectively. Ar gas was applied as a plasma source and N2 gas was used as a reactive gas as well as additional nitrogen source. To analyze the mechanism of obtaining new materials with high hardness by combining soft amorphous material with hard crystalline material, in this study, we have mainly investigated the relationship between structure and hardness enhancement of the coating layers on the effects of different kind of layer and the crystallization of layers. The results show that microstructure of each layer and a new nanocrystalline material that deposited between a-BON thin film and nc-SiC thin film affect the hardness enhancement in multilayered a-BON/nc-SiC thin films. Hardness obtained from a-BON was about 10 GPa. However, we could obtain strong hardness enhancement in a multilayered a-BON/nc-SiC thin film up to 36 GPa.