Crystal growth of MgO thin films deposited on ZnO underlayers by magnetron sputtering

The effect of ZnO underlayers on the crystal growth of MgO thin films was investigated. MgO single layers and double-layered coatings consisting of ZnO/MgO were deposited on unheated soda-lime silicate glass substrates by magnetron sputtering. X-ray diffraction measurement revealed that the MgO single layers were poorly crystallized even if the MgO thin films were deposited at various oxygen gas flow ratios and at various gas pressures. Moreover, it was observed that the ZnO/MgO coatings exhibited a preferred orientation along MgO(200) and that well-crystallized MgO thin films with very small thickness (10 nm) could be obtained using ZnO underlayers. This improvement in MgO thin films should be caused by heteroepitaxial-like growth of MgO{100} on ZnO{001} crystal lattice planes. In addition, the possible mismatch between MgO and ZnO atomic arrangements was estimated to be 8.2%.

► Double-layered coatings (ZnO/MgO) were deposited by magnetron sputtering.
► MgO thin films were better crystallized using ZnO underlayers.
► Crystallization should be caused by heteroepitaxial-like growth.