Titanium dioxide (TiO₂) has been extensively studied as a catalyst for a variety of potential applications, and there is a specific need for fundamental studies to address how adsorbates interact with TiO₂ surfaces, and how we can tailor their structures to better harvest the catalytic and photocatalytic properties.

 

In the first part of this talk, I will present our scanning tunneling microscopy (STM) studies of H₂O, O₂, and their interactions on rutile TiO₂(110) surfaces under ultra-high vacuum. By tracking the same surface area before and after molecule exposure, we study the adsorption, dissociation, diffusion, and reaction processes. We show that additional information can be derived by comparing the STM results with ensemble-averaged techniques such as temperature programmed desorption (TPD) and electron stimulated desorption (ESD). The experimental results are also compared with density functional theory (DFT) calculations for a better understanding of the reaction mechanisms. In the second part, I will present our efforts in the growth and characterization of pure and doped anatase TiO₂ thin films grown by molecular beam expitaxy. Structural excellent, epitaxial anatase TiO₂(001) films with (4x1) surface reconstructions are grown on Nb doped SrTiO₃(001) substrates. While pure anatase thin films are photoactive in the UV region, we show that controlled nitrogen doping can effectively extend the photo activity to the visible region.

 

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