Microstructure and optical properties of MgxZn1-xO thin films grown by means of pulsed laser deposition

The single-phase epitaxial MgxZn1-xO (0.4 < x < 0.9) alloy films with wide band gap have been deposited on cubic LaAlO3 (LAO) (100) substrates by pulsed laser deposition (PLD). X-ray diffraction measurement and TEM photograph indicate that the cubic phase could be stabilized up to Zn content about 0.6 without any phase separation. Films and substrates have a good heteroepitaxial relationship of (100) MgxZn1-xO||(100)LAO (out-of-plane) and (011)MgxZn1-xO||(010)LAO (in-plane). The lattice parameters a of MgxZn1-xO films increase almost linearly with increasing ZnO composition, while the band gap energy of the materials increases from 5.17 to 5.27 eV by alloying with more MgO. The cross-section morphology reveals layer thickness of about 250-300 nm and AFM scan over a 30 μm x 30 μm area reveals a surface roughness Ra of about 100 nm