Structural characterization of Zn₂SnO₄ epitaxial single crystal films prepared on c-cut -Al₂O₃ films by magnetron sputtering

Amorphous zinc stannate (Zn2SnO4) films were deposited on alpha-Al2O3 (0006) substrate by magnetron sputtering. And single crystal Zn2SnO4 films were obtained after thermal-annealing. The structural and optical properties of Zn2SnO4 films at different annealing temperatures were systematically studied. The structural analyses revealed that the sample annealed at 900 C exhibited the best crystallization quality with an inverse spinel structure. The heteroepitaxy mechanisms were further elucidated by XRD and HETEM. The epitaxial relationship between thin film and substrate can be concluded as Zn2SnO4 (111)//alpha-Al2O3 (0006) with Zn2SnO4 [0 11]//alpha-Al2O3 < 1 100>. The obtained Zn2SnO4 films showed excellent transparency with an average transmittance of 88.8% in the visible region. The optical band gaps of Zn2SnO4 films annealed at temperatures ranging from 600 to 1100 C was found to be within the range of 3.7-4.2 eV.