Hafnium oxide thin films: Effect of growth parameters on oxygen and hafnium vacancies

Thin films of hafnium oxide were grown by reactive molecular beam epitaxy. The growth parameters, substrate temperature, and oxidation conditions were varied in a wide range in order to investigate their influence on the thin film characteristics. The oxidation conditions during growth were decisive to hafnium oxide film orientation on c-cut sapphire substrates; it was possible to grow single oriented (00l) or (−111) oriented hafnium oxide films depending upon the oxidation conditions. The authors could successfully grow hafnium oxide thin films with oxygen or hafnium vacancies, depending on the oxidation conditions during growth, evident from optical band gap measurements. All the hafnium oxide thin films investigated in this study, irrespective of oxygen/hafnium vacancies, failed to show any ferromagnetic characteristics.