Identifying the effect of photo-generated carriers on the phonons in rutile TiO₂ through Raman spectroscopy

Investigating lattice vibrations through Raman spectroscopy is a crucial method for studying crystalline materials. Carriers can interact with lattices and influence lattice vibrations; thus, it is feasible to study the effect of photo-generated carriers on phonons by analyzing changes in the Raman spectra of semiconductors. Rutile is one of the predominant crystalline phases of TiO₂, which is a widely utilized metal oxide semiconductor. In this work, rutile TiO₂ is coated on a thinned optical fiber to concentrate ultraviolet light energy within the material, thereby enhancing the generation of carriers and amplifying the changes in the Raman spectra. A Raman detection laser with a wavelength of 532 nm is utilized to collect the Raman spectra of rutile TiO₂ during irradiation. Using this setup, the impact of photo-generated carriers on the phonons corresponding to Raman vibrational modes is researched. The localization and non-radiative recombination of photo-generated carriers contribute to a reduction in both the frequencies and lifetimes of phonons. This work provides a novel approach to researching the effect of carriers on phonons.