Substrate temperature dependence of structure and optical properties of ZnTiO3:Er3+/Yb3+ thin films synthesized by pulsed laser deposition

S J Mofokeng; F V Molefe; R E Kroon; H C Swart; T P Mokoena; M S Dhlamini; M J Sithole; L L Noto

doi:10.1016/j.heliyon.2023.e16259

Substrate temperature dependence of structure and optical properties of ZnTiO₃:Er³⁺/Yb³⁺ thin films synthesized by pulsed laser deposition

Heliyon. 2023 May 12;9(5):e16259. doi: 10.1016/j.heliyon.2023.e16259. eCollection 2023 May.

Authors

S J Mofokeng¹, F V Molefe², R E Kroon³, H C Swart³, T P Mokoena³, M S Dhlamini¹, M J Sithole¹, L L Noto¹

Affiliations

¹ Department of Physics, College of Science Engineering and Technology, University of South Africa, Johannesburg, 1710, South Africa.
² Department of Physics, Tshwane University of Technology, Private Bag X680, Pretoria, 0001, South Africa.
³ Department of Physics, University of the Free State, Bloemfontein, ZA9300, South Africa.

Abstract

ZnTiO₃:Er³⁺,Yb³⁺ thin film phosphors were successfully deposited by pulsed laser deposition (PLD) at different substrate temperatures. The distribution of the ions in the films was investigated and the chemical analysis showed that the doping ions were homogeneously distributed in the thin films. The optical response of the phosphors revealed that the reflectance percentages of the ZnTiO₃:Er³⁺,Yb³⁺ vary with the silicon substrate temperature due to the differences in the thickness and morphological roughness of the thin films. Under 980 nm diode laser excitation, the ZnTiO₃:Er³⁺,Yb³⁺ film phosphors displayed up-conversion emission from the Er³⁺ electronic transitions, with violet, blue, green, and red emission lines at 410, 480, 525, 545 and 660 nm from ²H_9/2 → ⁴I_15/2, ⁴F_7/2 → ⁴I_15/2, ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions, respectively. The up-conversion emission was enhanced by increasing the silico (Si) substrate temperature during the deposition. Based on the photoluminescence properties and decay lifetime analysis, the energy level diagram was established and the up-conversion energy-transfer mechanism was discussed in detail.

Keywords: Cross relaxation; Er3+/Yb3+ co-doped zinc titanate; Photons; Up-conversion mechanism; ZnTiO3 XPS.