Synthesis of local epitaxial α-(Cr1 − xAlx)2O3 thin films (0.08 ≤ x ≤ 0.16) on α-Al2O3 substrates by r.f. magnetron sputtering

(0001) oriented nanocrystalline α-(Cr1-xAlx)2O3 (0.08 ≤ x ≤ 0.16) thin films with an average thickness of ~ 270 nm were grown on c-plane α-Al2O3 (0001) single crystal substrates at 400 °C by non-reactive r.f. magnetron sputtering by a combinational approach using a segmented ceramic target. The stoichiometric composition of the films was determined by electron probe micro-analysis (EPMA). The composition dependent crystallization behavior of the α-(Cr1 − xAlx)2O3 thin films was characterized by detailed X-ray diffraction (XRD) analyses (i.e. XRD in Bragg-Brentano geometry, Rocking curve, Pole figure, Reciprocal space mapping (RSM)). Transmission electron microscopy (TEM) was carried out to study the microstructure and describe the orientation and epitaxial relationship between the films and the substrates. Further, Raman spectra show a significant shift of phonon frequency with Al concentration.