Evolution of enhanced crystallinity and mechanical property of nanocomposite Ti-Si-N thin films using magnetron reactive co-sputtering

摘要

Nanocomposite Ti-Si-N thin films (nc-TiN/a-SiN_x or nc-TiN/a-TiSi_xN_y) were deposited on Si(l 00) substrates from pure Ti and Si targets by magnetron reactive co-sputtering with a negative bias of -150V. The effects of N_2 flow ratio (FN_2% = FN_2/(FAr + FN_2) x 100%) and Ti power on the evolution of enhanced crystallinity and mechanical properties of Ti-Si-N have been investigated. The crystallinity, morphology, microstructure, elemental composition and mechanical properties of films were characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy, energy dispersive spectroscopy and nanoindentation, respectively. When both Ti and Si target powers were fixed at 100 W, the GIXRD pattern of Ti-Si-N at 3 FN_2% exhibited a broad peak corresponding to quasi-amorphous microstructure with nanocrystalline grains embedded in an amorphous matrix. Then Ti-Si-N films showed high amount of crystallization with multiple diffraction peaks at 5 FN_2%, but the reduced peak intensity formed at 7 FN_2% and even to be amorphous films without any peak at high 10-20 FN_2%. The measured mean hardnesses of Ti-Si-N films formed at 3, 5, 7, 10 and 20 FN_2% were 18.1, 21.5, 20.4, 17.8 and 15.7 GPa, respectively. Based on the high-hardness Ti-Si-N at constant 5 FN_2%, changing Ti target power from 75 to 200 W could greatly enhance the hardness from 19.0 to 32.0 GPa. Also, the main diffraction of nanocrystalline TiN (nc-TiN) in Ti-Si-N showed poly-orientation from (111), (200) and (220) planes, and the dominant preferred orientation of nc-TiN is along (200) plane normal. The relationship among parameters, crystallinity and mechanical properties of Ti-Si-N has further been discussed and correlated.