In a recent article published in Nanotechnology, researchers led by Hiroshi Onishi of Kobe University, Japan, and Geoff Thornton of University College London, UK, report on their ability to alter the surface structure of TiO2(110) from a few nanometres down to the atomic scale. The team used a scanning tunnelling microscope (STM) to map the surface and then to apply electrical pulses in the mapped areas.
Pulses at 3 V removed individual hydrogen atoms, which usually contaminate these surfaces. Similarly, scanning an area at 3 V created H-free areas. Oxygen vacancies appear similar to H-atoms in STM images so the H-free areas allowed easy probing of the reactivity of the vacancies. In this way, the team resolved two issues pertinent to photocatalysis - both water and oxygen were shown to split in the vacancies.
More energetic pulses, between 5-10 V, created circles of the 1x2 reconstruction, 6-8 nm in diameter. "Arrays of these reconstructions could be used as templates to direct the growth of organic molecules or metal nanoparticles," said team member Chi Lun Pang. This could ultimately lead to multi-functional surfaces or even allow nanoscale circuitry to be laid.
These templating experiments, together with investigations establishing how far the methodology can be transferred to other surfaces, are likely to feature in future research.