X-ray Diffraction Investigation of Stainless Steel-Nitrogen Thin Films Deposited Using Reactive Sputter Deposition

An X-ray diffraction investigation was carried out on nitrogen-containing 304 stainless steel thin films deposited by reactive rf magnetron sputtering over a range of substrate temperature and bias levels. The resulting films contained between similar to 28 and 32 at.% nitrogen. X-ray analysis was carried out using both the standard Bragg-Brentano method as well as area-detector diffractometry analysis. The extent of the diffraction anomaly ((002) peak shift) was determined using a calculated parameter, denoted R-B, which is based on the (111) and (002) peak positions. The normal value for R-B for FCC-based structures is 0.75 but increases as the (002) peak is anomalously displaced closer to the (111) peak. In this study, the R-B values for the deposited films were found to increase with substrate bias but decrease with substrate temperature (but still always >0.75). Using area detector diffractometry, we were able to measure d(111)/d(002) values for similarly oriented grains within the films, and using these values calculate c/a ratios based on a tetragonal-structure model. These results allowed prediction of the (002)/(200) peak split for tetragonal structures. Despite predicting a reasonably accessible split (similar to 0.6 degrees-2.9 degrees-2 theta), no peak splitting observed, negating the tetragonal-structure hypothesis. Based on the effects of film bias/temperature on R-B values, a defect-based hypothesis is more viable as an explanation for the diffraction anomaly.