Structural, microstructural, and optical properties of Zn_(1-x)Mg_xO thin films grown onto glass substrate by ultrasonic spray pyrolysis

摘要

Pure and doped Zn_(1-x)Mg_xO films were deposited onto glass substrate by ultrasonic spray pyrolysis technique. The variation of lattice constant and the blue shift of near-band-edge emission indicate that Zn~(2+) ions are successfully substituted by Mg~(2+) ions within ZnO lattice. At higher Mg content (x ≥ 0.21), a drastic change appears in the morphology, as a result of structural changes from wurtzite (ZnO) structure into a mixture of wurtzite and cubic (MgO) phases. FTIR study indicated the existence of distinct characteristic absorption peaks at ~442 cm~(-1) for Zn-O stretching mode that shifted toward the red region with the increase in Mg content. In addition to the host phonons of ZnO, one additional band was observed around 523 cm~(-1), presumably attributed to the Mg-related vibrational mode. The optical constants and thickness of thin films have been determined using experimental transmittance data. The luminescence intensity at 2.63 eV of Zn_(0.85)Mg_(0.15)O thin films was found to be approximately 13 times higher than that of pure ZnO film measured under the same excitation conditions.