Nanostructured CrN thin films prepared by reactive pulsed DC magnetron sputtering

Abstract

High quality chromium nitride (CrN) films have been deposited onto silicon (1 0 0) substrates using pulsed DC magnetron sputtering of pure Cr target at different gas mixtures of argon and nitrogen and in the substrate temperature range 303–973 K. At low N 2 flow rates (<2 sccm), only pure Cr is detected, while at the intermediate flow rates (5 sccm), the hexagonal and cubic phases of Cr–N (Cr 2N and CrN) are obtained. At higher flow rates, in the range of 10–25 sccm, only cubic CrN phase is obtained. The films prepared at different substrate temperatures and at 10 sccm of nitrogen flow rate indicated the formation of cubic CrN phase at room temperature and the phase formed is found to be stable up to 973 K. The deposition of the films as a function of nitrogen flow rate and substrate temperatures indicated that the good quality crystalline films could be formed at 773 K, 10 sccm of nitrogen flow rate. The Cr 2p 3/2 and N 1s of XPS spectra also confirmed the formation of CrN phase. Determination of the texture coefficients of the CrN films as a function of substrate temperature showed that the preferred orientation changes from [1 1 1] to [1 0 0]. Deposition as a function of nitrogen flow rates and substrate temperatures showed significant changes in the morphology and RMS surface roughness, which could be related to the difference in the growth mechanism of the CrN films. Measurement of nanomechanical properties on typical films deposited on titanium modified stainless steel substrates at optimum conditions show hardness of 12 ± 1.81 GPa, Young's modulus of about (250 ± 51.28 GPa) and coefficient of friction of 0.16.