Production of Ti films with controlled texture

Abstract

This paper investigates the effects of (i) the substrate bias; (ii) the mixing of one or several additional elements with Ti; (iii) plasma nitriding of the presputtered film; and (iv) the film deposition rate on the structural properties of pure Ti and Ti-based films. The Ti-based films investigated were: Ti−SS (stainless steel), Ti−6A1-4V, Ti−Cu and Ti−Cr. The films were sputtered onto steel and glass substrates using a d.c. magnetron. The negative substrate bias Us used in the magnetron sputter ion plating process varied over a very wide range from 0 to −1500 V. The structural properties of the films were characterized by means of X-ray diffraction. Dramatic differences in the development of the crystal orientation with increasing negative bias for pure Ti and Ti-based films were found. While the pure Ti films were polycrystalline for all values of Us, the Ti-based films were formed not only as polycrystalline but also as amorphous or nanocrystalline substances, characterized by very broad (FWHM up to 10°) reflection lines with very low intensities. The formation of nanocrystalline films is strongly dependent on the type and quantity of additional elements with Ti. Additionally, it was found that at a certain threshold value of the deposition rate the preferred orientation of pure Ti film switches from (002) to (010). This abrupt change in the film texture shows that there is a physical constraint on the maximum deposition rate if the resultant films are to have the same structural properties.