In-plane lattice orientation in aluminum scandium nitride epitaxial films deposited on Nb-doped SrTiO₃(111) substrates via reactive magnetron sputtering

Abstract

Wurtzite-type aluminum scandium nitride [WZ-(Al_1−xSc_x)N] thin films were grown on 0.5 wt % Nb-doped SrTiO₃(111) (Nb:STO) single crystal substrates using the radio frequency reactive magnetron sputtering method with Al and Sc targets. WZ-(Al_1−xSc_x)N thin films with 0 ≤ x ≤ 0.49 were epitaxially grown on Nb:STO substrates. Films with x ≤ 0.3 exhibited multi-domain in-plane orientation. The coexistence of two rotation domains, (Al,Sc)N[100]//Nb:STO[110] and (Al,Sc)N[100]//Nb:STO[112], was observed. The abundance of these two domains varied with x, and films with x > 0.3 were single-crystal-like single-domain films. Although the lattice parameters and domain structure intricately changed with x, the calculated unit cell volume was in accordance with the Vegard’s law. These results indicate that the unit cell volume is determined by the chemical composition.