TiO2 is a versatile wide bandgap transparent semiconducting oxide with three well known polymorphs: Anatase, Rutile and Brookite. These crystal structures are desired for many industrial applications mainly for their photocatalytic activity, oftentimes in thin-film form. Thin-film crystalline polymorphs of TiO2 are often made by physical vapor deposition on a...
Spectroscopic ellipsometry (SE) is used to characterize amorphous and crystalline thin films of TiO2. Amorphous precursor films of TiO2 are deposited by radio frequency magnetron sputtering on fused silica and silicon substrates. Annealing the amorphous precursor films induces them to crystallize into either pure or mixed phases of the three...
TiO₂ typically crystallizes into three polymorphs: brookite, rutile, and anatase. The phase selection problem in TiO₂ is the lack of understanding what conditions cause amorphous TiO₂ to crystallize into one of its three polymorphs during an annealing process. It has been recently shown that phase selection in TiO₂ is highly...
The electrical properties of amorphous and crystalline titanium dioxide polymorphs are reported. Titanium dioxide is a widely used transparent semiconductor and it is a useful oxide model. Using variable temperature transport measurements of thin films, it was possible to establish the activation energy barrier for conduction. This was accomplished using...
This study used SCOUT optical modelling software to create models of the reflectance and transmittance spectra generated by mixtures of titanium dioxide (TiO2) and tin oxide (SnO2). These models enabled identification of how altering the ratio of a mixture changes the optical response. By being able to identify how altering...
The optical transition in high-fraction polymorphs of titania (TiO2) were investigated to determine the band gap behavior of the most common polymorphs—brookite, rutile, and anatase—the values of which are varied in the literature. The direct optical band gaps of brookite, rutile, and anatase, were determined to be 3.37(7)eV, 3.41(11)eV and...
This work explores the synthesis and characterization of the metastable alloys Sn1-xCaxCh (Ch= S, Se) and nitride compounds Zn-W-Mo-N, which have recently been predicted by theorists. Single phase thin films of Sn1-xCaxS are prepared by pulsed laser deposition and radio-frequency magnetron sputtering and of Sn1-xCaxSe are prepared by pulsed laser...
Structure-specific synthesis processes are of key importance to the growth of polymorphic functional compounds such as TiO₂, where material properties strongly depend on structure as well as chemistry. The robust growth of the brookite polymorph of TiO₂, a promising photocatalyst, has been difficult in both powder and thin-film forms due...