Effects of Substrate Temperature on Optical, Structural, and Surface Properties of Metal-Organic Vapor Phase...

MgZnO possesses a tunable bandgap and can be prepared at relatively low temperatures, making it suitable for developing optoelectronic devices. MgZn_1-O (x~0.1) films were grown on sapphire by metal-organic vapor phase epitaxy under different substrate-growth temperatures T_s of 350-650 °C and studied by multiple characterization technologies like X-ray diffraction (XRD), spectroscopic ellipsometry (SE), Raman scattering, extended X-ray absorption fine structure (EXAFS), and first-principle calculations. The effects of T_s on the optical, structural, and surface properties of the Mg_0.1Zn_0.9O films were studied penetratively. An XRD peak of nearly 35° was produced from Mg_0.1Zn_0.9O (0002) diffraction, while a weak peak of ~36.5° indicated MgO phase separation. SE measurements and analysis determined the energy bandgaps in the 3.29-3.91 eV range, obeying a monotonically decreasing law with increasing T_s. The theoretical bandgap of 3.347 eV, consistent with the SE-reported value, demonstrated the reliability of the SE measurement. Temperature-dependent UV-excitation Raman scattering revealed 1LO phonon splitting and temperature dependency. Zn-O and Zn-Zn atomic bonding lengths were deduced from EXAFS. It was revealed that the surface Mg amount increased with the increase in T_s. These comprehensive studies provide valuable references for Mg_0.1Zn_0.9O and other advanced materials.