Helena Cristina Vasconcelos is an Associate Professor at the Faculty of Science and Technology of Azores University, Portugal. She holds a bachelor's degree in Physics and Materials Engineering, awarded in 1990 by the Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa (FCT NOVA), and a PhD in Materials Engineering, which she completed in 1999 at the Instituto Superior Técnico (IST), Lisbon.
Biomedical Engineering, Radiation Physics, Optical Materials, Fluorescence, and Photonics
This presentation explores the structural and electronic transformations of sol-gel-derived metal oxide thin films, focusing on the interplay between annealing-induced phase evolution and photonic properties. Using titanium dioxide (TiO?) thin films as a model system, we examine the transitions that occur as the films progress from an amorphous phase to anatase, then to mixed anatase-rutile, and ultimately to rutile phases as the annealing temperature increases. These phase changes are characterized using advanced vacuum ultraviolet (VUV) spectroscopy (< 200 nm), which reveals critical information about the material’s electronic structure. Key spectral features, such as the σ → π* transition, which is associated with bonding to antibonding orbital excitations, as well as the π → π* and t2g(π)→t*2g(π*) transitions, are observed. These features highlight the material's intrinsic electronic states and the effects of defects on its optical behavior.
The findings emphasize the crucial role of understanding the relationship between material structure and optical properties in the development of photonic and optoelectronic technologies. By mapping these structural and electronic transitions, the study provides a deeper understanding of how annealing parameters can be used to tune the photonic properties of TiO? thin films, advancing their potential applications in a range of optoelectronic devices.