NiO thin film with an extremely high index (7 overline{1 } 4) on r-plane sapphire substrate

Abstract

Thin film epitaxy is essential for state-of-the-art semiconductor applications. The combination of different substrates and deposition methods leads to various crystallographic orientation relationships between thin films and substrates, which have a decisive impact on thin film performance. By utilizing pulsed laser deposition, we discovered a very high-index (7 overline{1 } 4)–oriented NiO thin film when deposited on r-plane text{(10}overline{1}text{2)} sapphire substrates. The in-plane epitaxial relations are {[13overline{1 }]}_{text{NiO}}text{||[1}overline {2}{text{10]}}_{text{Sapphire}} and {[overline{1 }12]}_{text{NiO}}text{||[10}overline{11}{text{]}}_{text{Sapphire}}, and the lattice mismatch is 3.2% and 0.4% along two directions, respectively. Exchange bias studies by the deposition of Co on NiO (111) and NiO (7 overline{1 } 4) show different behaviors, which may be associated with the spin density and alignment on the surface.Graphical abstract