Preparation of titanium carbon nitride films by reactive high power pulsed sputtering Penning discharges

Abstract

Titanium carbon nitride (TiCN) films are prepared by reactive high power pulsed sputtering (HPPS) Penning discharges at a total pressure of 0.7 Pa and an average power of about 60 W, where the N2 fraction is 5%. The area ratio (RTC) of carbon target to the overall target is increased from 0 to 50%. This system can be regarded as a kind of double HPPS system with simultaneity. The peak value of the instantaneous power ranges between 3 and about 16 kW. It means that the peak power density range corresponds to 0.3–1.3 kWcm−2.The film hardness of 30 GPa and more and the elastic modulus of 200–240 GPa do not strongly depend on RTC at RTC less than 25%, beyond which they decrease to 15.8 GPa and 122 GPa. However, the value of the compressive stress and the friction coefficient gradually decrease with the increase in RTC. X-ray diffraction peak of (111) texture is observed for the films prepared at RTC less than 25%, showing the grain size of about 8–15 nm. On the other hand, the hardness and the value of the stress increase with the increase in the dissipated energy per pulse (Ep) at RTC less than 25%. Chemical compositions and bonding states of films are investigated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) - electron energy loss spectroscopy (EELS). Based on XPS measurements, the relative content of C increases from 2.8 to 65% with the increase in RTC. On the other hand, the relative content of N is close to that of Ti and it decreases from 46 to 17%. The intensity of the peak related to Ti-N bond is largest among all intensities of the peaks related to the binary or ternary compounds including Ti component, whereas the intensity related to sp2 C-C bond increases with RTC. These intensity ratios depend on RTC, but they are not sensitive to Ep.