title: Upconversion emission from Yb3+ and Tm3+ codoped NaYF4 thin film prepared by thermal evaporation.
abstract: Yb3+ and Tm3+ codoped fluoride thin film, with intense ultraviolet and visible upconversion emissions under 980 nm excitation, has been deposited on an Al2O3 ceramic substrate by thermal evaporation under high vacuum. NaY(0.835)Yb(0.15)Tm(0.015)F4 bulk material synthesized by high temperature solid-state reaction was used as target in preparing the thin film. Yb3+ and Tm3+ codoped system, which had been reported before, had been studied. Compared with the unannealed thin film, the annealed film showed better upconversion emission properties, especially in the ultraviolet region, given in the normalized upconversion emission spectra, due to the structure changed from amorphous to hexagonal NaYF4 (beta-NaYF4) during the annealing process. The upconversion mechanism of the thin film was also discussed in this paper.
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University Changchun 130012, P. R. China.
authors.forename: Zhixu
authors.initials: Z
authors.lastname: Jia
authors.forename: Kezhi
authors.initials: K
authors.lastname: Zheng
authors.forename: Daisheng
authors.initials: D
authors.lastname: Zhang
authors.forename: Dan
authors.initials: D
authors.lastname: Zhao
authors.forename: Weiping
authors.initials: W
authors.lastname: Qin