Structural and Raman Scattering Properties of ZnO:Al Thin Films Sputter-Deposited at Room Temperature

Abstract

Structural and Raman scattering properties of Al-doped ZnO (ZnO:Al) thin films grown by radio-frequency (RF) magnetron sputtering at room temperature has been investigated. Coupled with the low temperature-deposition, the RF power was found to have profound influence on various film properties. An increase in the RF power effected an unusual deterioration of preferred c-axis orientation and increased polycrystallinity accompanied by a progressive transformation from a dense columnar to a non-columnar and faceted grain structure. Raman spectra of the films showed phonon modes at ∼274, 475 and 505 cm −1 , which are unusual of wurtzite ZnO. The origin and evolution of these modes have been elucidated by comparing these spectra with those of undoped ZnO films grown under identical conditions and by correlating their intensity variation with RF power. It has been shown that although manifestation of all three modes is associated with the Al dopant incorporation in the films, their intensity evolution is distinctly affected by the RF power-dependent carrier concentration n and disorder in the films.

Microstructural evolution of sputtered ZnO thin films with rapid thermal annealing

“…Zinc oxide (ZnO) thin films have engrossed considerable interest now a days, due to its excellent material properties like piezoelectricity, large bandgap of 3.37 eV at room temperature and higher exciton binding energy (60 MeV), which is nearly two and half times greater than other direct bandgap semiconductors like gallium nitride (GaN) [1][2][3]. Therefore, ZnO is currently used as multifunctional electronic material having applications in numerous areas such as light emitting diodes, laser diodes, varistors, piezoelectric transducers, field-effect transistors, touch display panels, flat panel displays, photovoltaic solar cells, and gas sensors due to its high electrochemical stability, nontoxic nature, and ease of fabrication [4][5][6].…”