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

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 1 ¯ 4) –oriented NiO thin film when deposited on r-plane (10 1 ¯ 2) sapphire substrates. The in-plane epitaxial relations are [13 1 ¯] _NiO||[1 2 ¯ 10] _Sapphire and [1 ¯ 12] _NiO||[10 11 ¯] _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 1 ¯ 4) show different behaviors, which may be associated with the spin density and alignment on the surface. Graphical abstract: [Figure not available: see fulltext.].