High intensity orange-red emission of chemically deposited Sm3+-doped ZrO2 thin films - Beneficial effects of host and dopant

Abstract

Samarium doped (0.5–5 at.%) ZrO2 films with high surface and optical quality were obtained by sol–gel method using inorganic zirconium precursor. The morphology and roughness of the samples were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). A phase transition following the doping with Sm3+ ions was registered by the X-ray diffraction (XRD) method, leading to stabilization of the tetragonal ZrO2 phase. Optical parameters such as refractive index and extinction coefficient were determined for each sample. X-ray photoelectron spectroscopy (XPS) revealed the presence of carbon impurities as well as a shift of the valence band (VB) edge to lower binding energies with the increase of the dopant level. The electron paramagnetic resonance (EPR) proved the presence of oxygen vacancies and other defects (Zr3+, T-centers) in the structure of the films which prompted photoluminescence (PL) in the material. The emission spectra of the pure ZrO2 and Sm-doped samples revealed the beneficial effect of the host matrix, capable of boosting the characteristic orange-red emission of the Sm3+ ions. The obtained films have very high ratio of acceptor/donor emission intensity (Ia/Id = 25) making them promising candidates for applications in the field of photonics, including in the development of white LEDs.

Keywords

• Zirconia
• Phase transformation
• Photoluminescence
• Rare earth dopant
• Optical properties