Nd-doped SiO2/TiO2 Bragg reflectors produced by sol-gel dip-coating deposition

Distributed Bragg reflectors (DBRs) are essential components in advanced optoelectronic and optical devices. Improving the optical properties of these multilayer structures is at the forefront of research because of their potential use in a variety of sectors, such as solar cells, lasers, sensing and photonics. Sol-gel film deposition is a well-established route for the realization of high-quality optical layers with controlled composition, thickness and optical properties. By using the sol-gel method, SiO2/2% at. Nd: TiO2 samples were prepared, with the aim to increase the reflectivity in a broad optical region and to provide specific spectral emissions related to Nd3+ ions. The prepared samples have been characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Atomic Force Microscopy (AFM), UV-Visible spectrophotometry, and Photoluminescence (PL). The X-ray analysis revealed that all the samples exhibit an anatase phase, with crystallite sizes ranging from 5.13 to 12.51 nm. AFM topography showed a flat and homogeneous surface with a root mean square (RMS) roughness ranging from 0.19 to 0.28 nm. UV-vis spectrophotometry revealed a low transmission of 0.3% by using only a few alternating layers. Finally, PL analyses reported the active role of Nd3+ ions as optical emitters. All these results indicate that the DBRs are promising to be good for advanced optical applications.[GRAPHICS]