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Single-phase, high band gap energy Zn0.5Mg0.5O films were grown under oxygen pressure, using pulse laser deposition with a Zn0.5Mg0.5O target. Structural characterization studies revealed that the crystal structures of the ZnX-1MgXO films could be controlled via changes in the oxygen pressure. TEM analysis showed that the thickness of the deposited Zn1-xMgxO thin films was 50–75 nm. As the oxygen pressure increased, we found that one axis of the crystals did not show a very significant increase in the crystallization compared with that observed at low oxygen pressure. The X-ray diffraction peak intensity for the hexagonal-ZnMgO (002) plane increased relative to that for the cubic-ZnMgO (111) plane. The corresponding c-axis of the h-ZnMgO lattice constant increased from 5.141 to 5.148 Å, and the a-axis of the c-ZnMgO lattice constant decreased from 4.255 to 4.250 Å. EDX analysis showed that the Mg content in the mixed-phase ZnMgO films decreased significantly, from 54.25 to 46.96 at.%. As the oxygen pressure was increased from 100 to 150 mTorr, the absorption edge red-shifted from 3.96 to 3.81 eV; however, a film grown at the highest oxygen pressure tested here (200 mTorr)., {"references":["V. Srikantand D.R. Clarke, \"On the optical band gap of Zinc oxide,\"J. Appl. Phys. Vol. 83, pp. 5447-5451, 1998.","P. Bhattacharya, R.R. Das, and R.S. Katiyar, \"Fabrication of stable wide-band-gap ZnO/MgO multilayer thin films,\"Appl. Phys. Lett. Vol. 83, pp. 2010-2012, 2003.","M.H. Liang, Y.T. Ho, W.L. Wang, C.Y. Peng, and L. Chang, \"Growth of ZnMgO/ZnO films on r-plane sapphires by pulsed laser deposition,'J. Crystal Growth Vol. 310, pp.1847-1852, 2008.","I. Takeuchi, W. Yang, K.S. Chang, M.A. Aronova, T. Venkatesan, R.D. Vispute, and L.A. Bendersky,\"Monolithic multichannel ultraviolet detector arrays and continuous phase evolution in MgZnOcompositin spreads,\" J. Appl. Phys. Vol. 94, pp. 7336-7340, 2003.","Y. Chen, H.J. Ko, S.K. Hong, and T. Yao, \"Layer by layer growth of ZnOepilayer on Al2O3(0001) by using a MgO buffer layer,\"Appl. Phys. Lett. Vol. 76, pp.559-561, 2000.","A. Ohtomo, M. Kawasaki, T. Koida, K. Masubuchi, H. Koinuma, Y. Sakurai, Y. Yoshida, T. Yasuda, and Y. Segawa,\"MgZnO as a II-V wideband gap semiconductor alloy,\" Appl. Phys. Lett. Vol. 72 pp. 2466-2468, 1998.","C.Y. Liu, H.Y. Xu, L. Wang, X.H. Li, and Y.C. Liu, \"Pulse laser deposition of high Mg-content MgZnO films: Effects of substrate and oxygen pressure,\"J. Appl. Phys. Vol. 106, pp. 073518-1-073518-4, 2009.","Z.G. Ju, C.X. Shan, D.Y. Jiang, J.Y. Zhang, B. Yao, D.X. Zhao, D.Z. Shen, and X.W. Fan, \"MgZnO based photodetectors covering the whole solar-blind spectrum range,\"Appl. Phys. Lett. Vol. 93, pp. 173505-1-173505-3, 2008.","B.P. Zhang, N.T. Binh, K. Wakatsuki, C.Y. Liu, Y. Segawa, and N. Usami, \"Growth of ZnO/ZnMgO quantum wells on sapphire substrates and observation of the two-dimensional confinement effect,\" Appl. Phys. Lett. Vol. 86, pp. 032105-1-032105-3, 2005.\n[10]\tJ. Z, Chen, C-H. Li, and I-C. Cheng, \"Phase transition of room temperature RF-sputtered ZnO/MgZnO multilayer thin films after thermal annealing,\"Thin Solid Films Vol.520, pp.1918-1923, 2012.\n[11]\tZ. Vashaei, T. Minegishi, H. Suzuki, T. Hanada, M.W. Cho, T. Yao, and A. Setiawan,\"Structure variation of cubic and hexagonal MgZnO layer grown on MgO(111)/c-sapphire,\"J. Appl. Phys. Vol. 98, pp. 054911-1-054911-4, 2005.\n[12]\tX. Chen and J. Kang,\"The structural properties of wurtzite and rocksalt MgZnO,\"Semicond. Sci. Technol.Vol. 23, pp. 025008, 2008.\n[13]\tA. Kaushal and D. Kaur,\"Effect of Mg content on the structural, electrical and optical properties of ZnMgO nanocomposite thin films,\"Solar Energy Materials & Solar Cells Vol. 93 pp. 193-198, 2009."]}