Growth of thin‐film niobium and niobium oxide layers by molecular‐beam epitaxy

The ultrahigh vacuum technique of molecular‐beam epitaxy (MBE) has been successfully employed in growing highly oriented polycrystal and single‐crystal niobium oxide layers on z‐cut LiNbO3 substrates. A new variant of the monoxide has been grown and characterized, and the potential advantages and limitations of MBE for growing the higher oxides, such as Nb2O5, are put forward. Niobium metal layers have also been grown on z‐cut LiNbO3. The deposition of excellent quality niobium oxide on α‐alumina (z‐cut sapphire) has been demonstrated, providing an optical waveguiding structure of large differential refractive index. Crystallinity and compositional data are presented for all the above layers. The post‐deposition oxidation of oxygen‐deficient films to the pentoxide has been studied in detail, and system requirements for the in situ growth of Nb2O5 proposed.