Infrared upconversion in radio frequency magnetron sputtered Er-doped zinc oxide thin films

摘要

Upconversion in radio frequency magnetron sputtered Er-doped zinc oxide thin films on Si substrate has been demonstrated using 1550nm cw laser excitation. As-sputtered thin films did not show any upconversion emission, and annealing was required to optically activate the Er~(3+)-ions. Emissions at 985, 809, and 665-675 nm were observed in annealed thin films, corresponding to transitions from ~4I_(11/2), ~I_(9/2), and ~4F_(9/2) to the ground state ~4I_(15/2), respectively. The emission from ~4I_(11/2) was the dominant one, whereas emission from ~4I_(9/2) was the weakest. The highest intensity at 985 nm was obtained with 2.4 at. % of Er by annealing the film at 700 ℃. Annealing at higher temperatures causes Er to diffuse and segregate to the Si-ZnO interface between the Si substrate and the ZnO film.