Principal components analysis of Ti-Si-N nanocomposite thin films

Nanocrystalline TiN/SiN composite (nanocomposite) thin films were reactively co-sputtered from pure Ti and Si targets over the mid-frequency range of 50-250 kHz using two asymmetric bipolar pulsed direct current power supplies. The resulting films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and nanoindentation in addition to measurement of the plasma properties during deposition. Due to lengthy fabrication and characterization, only nine samples exist in this data set for films deposited at 10 mTorr in pure nitrogen. Using the Vickers hardness of the films as the response, a principal components analysis of 13 predictors comprised of characterization and plasma parameters was conducted to find which parameters are most responsible in determining the hardness. Principal component analysis was then applied to the data to capture the variable relationships graphically and to reduce the number of predictors to a set of components. A correlation matrix established that the percent (111) and (200) crystallographic orientation and the momentum-per-atom best explained the variation in hardness. The momentum-per-atom has shown promise as a universal variable, independent of sputter deposition system, and is a statistically sound predictor of hardness in Ti-Si-N thin films.