In addition, for E p<2 keV, the superstoichiometric Hf 3N 4 phase is also present in the films for higher ion doses. The remaining peak is not an XPS peak at all it is an Auger peak arising from x-ray induced Auger emission. For ion beam energies, E p⩾2 keV, the hafnium nitride films formed are a mixture of metallic hafnium, a substoichiometric hafnium nitride that could be associated with the trigonal ε-Hf 3N 2 and/or ξ-Hf 4N 3 phases, and the stoichiometric HfN phase. The most intense peak at 335 eV is due to emission from the 3d levelsof the Pd atoms, whilst the 3p and 3s levels give rise to the peaks at 534/561 eV and 673 eV respectively. FA results show that the composition of the hafnium nitride films depends on both the ion fluence and ion energy, the formation of the superstoichiometric Hf 3N 4 phase being limited by the ion beam energy. By means of FA of the Hf 4f and N 1s XPS core level peaks, comprising principal component analysis (PCA) and iterative target transformation factor analysis (ITTFA), the number and spectral shape of the different Hf–N phases formed during nitrogen implantation, as well as their concentrations, have been obtained without any prior assumptions. X-ray photoelectron spectroscopy (XPS) and factor analysis (FA) have been used to characterise the chemical composition of the films. Hafnium nitride thin films have been grown by “in situ” nitrogen implantation of metallic hafnium at room temperature over the energy range of 0.5–5 keV.
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