Identifying the influence of the intrinsic defects in Gd-doped ZnO thin-films

• Published in: Journal of applied physics 2016-02, Vol.119 (6)
• Main Authors: Flemban, T. H., Sequeira, M. C., Zhang, Z., Venkatesh, S., Alves, E., Lorenz, K., Roqan, I. S.
• Format: Article
• Language: English
• Subjects: Applied physics; Backscattering; Density functional theory; Gadolinium; Lattice vacancies; Optical properties; Oxygen; Photoluminescence; Point defects; Pulsed laser deposition; Pulsed lasers; Thin films; Zinc oxide
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4941434

Gd-doped ZnO thin films were prepared using pulsed laser deposition at different oxygen pressures and varied Gd concentrations. The effects of oxygen deficiency-related defects on the Gd incorporation, optical and structural properties, were explored by studying the impact of oxygen pressure during deposition and post-growth thermal annealing in vacuum. Rutherford Backscattering Spectrometry revealed that the Gd concentration increases with increasing oxygen pressure for samples grown with the same Gd-doped ZnO target. Unexpectedly, the c-lattice parameter of the samples tends to decrease with increasing Gd concentration, suggesting that Gd-defect complexes play an important role in the structural properties. Using low-temperature photoluminescence (PL), Raman measurements and density functional theory calculations, we identified oxygen vacancies as the dominant intrinsic point defects. PL spectra show a defect band related to oxygen vacancies for samples grown at oxygen deficiency.