Up-conversion luminescence and optical thermometry of Yb3+/Tm3+ co-doped AlN nanowires

Abstract

Due to its unique advantages including non-contact operation, high sensitivity, and exceptional spatial resolution, nanoscale optical thermometry has become an indispensable technique with widespread applications in micro/nanoelectronics, integrated photonic systems, and biomedical engineering. Here, Yb³⁺/Tm³⁺ co-doped AlN nanowires were successfully synthesized via an arc-discharge method. The nanowires, characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy, exhibit lengths of several micrometers and uniform diameters ranging from 10 to 20 nm, yielding a high aspect ratio. Under 980 nm excitation, the nanowires display distinct up-conversion (UC) luminescence, with emission bands at 544 nm (green), 654 nm and 691 nm (red), and 795 nm (near-infrared), corresponding to Tm³⁺ ion transitions. The AlN:Yb³⁺/Tm³⁺ nanowires show excellent optical thermometry performance, achieving a maximum relative sensitivity (S_r) of 3.32% K^-1 at 298 K and a temperature resolution (δT) of 0.009 K. These results underscore the potential of AlN:Yb³⁺/Tm³⁺ nanowires for advanced optical temperature sensing in nanotechnology, biomedical applications, and high-resolution thermal imaging.