Structural and band gaps studies of novel Al_2-xHf_xO₃ materials toward MOS applications

Developments of new materials for MOS applications are important due to the problems of downscaling of SiO₂. In this work, Hf doped Al₂O₃ materials were studied as a possible new material for use in metal oxide semiconductor (MOS) application. Novel Al_2-xHf_xO₃ (x = 0.001, 0.002 and 0.003) materials were prepared by a self-propagating combustion synthesis method. X-Ray diffraction (XRD) results showed that all samples were pure with hexagonal crystal structure. Quantitative analysis via Rietveld refinements showed that Hf was successfully substituted in the hexagonal Al₂O₃ crystal structure. The Hf content was confirmed via energy dispersive X-Ray spectroscopy (EDS). UV–visible spectroscopy showed that Al_2-xHf_xO₃ materials exhibited band gap narrowing with respect to pure Al₂O₃ materials and it is dependent on the Hf content following an exponential function.