Optical and Structural Properties of Ion-implanted InGaZnO Thin Films Studied with Spectroscopic Ellipsometry and Transmission Electron Microscopy

Amorphous InGaZnO (IGZO) thin films were grown using RF sputtering deposition at room temperature and their corresponding dielectric functions were measured In order to reduce defects and increase carrier concentrations, we examined the effect of forming gas annealing and ion implantation. The band gap energy increased with increasing forming gas annealing temperature We implanted the IGZO thin films with F(-) ions in order to decrease oxygen vacancies For comparison, we also implanted InO(-) ions. Transmission electron microscopy showed that the amorphous phase undergoes transformation to a nanocrystalline phase due to annealing We also observed InGaZnO(4) nanocrystals having an In-(Ga/Zn) superlattice structure. As the annealing temperature increased, the optical gap energy increased due to crystallization. After annealing, we observed an oxygen-vacancy-related 1.9 eV peak for both unimplanted and InO-implanted samples. However, F(-) ion implantation substantially reduced the amplitude of the 1 9 eV peak, which disappeared completely at a F fluence of 5 x 10(15) cm(-2). We observed other defect-related peaks at 3 6 and 4 2 eV after annealing, which also disappeared after F implantation (C) 2009 The Japan Society of Applied Physics