Formation of metastable rock salt ZnO on surface of cubic MgZnO thin films at low temperature by PLD method

• There are cubic ZnO on the surface of MgZnO thin film deposited at 150 °C.
• The MgZnO thin film could absorb UV light range from 220 to 300 nm.
• Cubic ZnO would form on the surface of MgZnO thin film.
• The Cubic ZnO is not stable at higher temperature under atmospheric environment.

Effect of temperature on crystal and optical characteristics of MgZnO thin films by PLD method was studied. MgZnO thin film that contained cubic ZnO on the surface was made at lower temperature, which could absorb UV light ranged from 230 to 300 nm. This curious phenomenon is reason from the vertical separation of Zn atoms from cubic structure MgZnO lattice through vertical migration under vacuum condition during growth process. And because the solid solubility of Zn atoms in cubic MgZnO increased with temperature, the cubic ZnO didn't form in MgZnO thin films deposited at higher temperature. The cubic ZnO could just exist through special separating out process during growth process, which would transformed gradually from cubic structure to hexagonal structure when annealed at temperature from 450 °C to 850 °C under atmospheric conditions.