Lippmaa, Mikk

Biography

Photocatalytic water splitting for hydrogen production presents an interesting challenge for oxide semiconductor development. The purpose is to design an oxide material that is chemically stable in water, has a bandgap of about 2 eV, and has high photocarrier mobility at room temperature. The first two requirements can be met by using noble metal doped SrTiO3, but the best photocatalysts, Ir:SrTiO3 and Rh:SrTiO3 have very low photocarrier mobilities. We study the possibility of avoiding the mobility problem by placing self-organized nanoscale metal electrodes inside the oxide semiconductor. Spontaneous noble segregation in a perovskite forms arrays of nanoscale metal pillars (Fig. 1), which can form Schottky-type depletion layers in the surrounding semiconductor (Fig. 2). The required photocarrier diffusion length thus becomes shorter and we can extract photogenerated charge very efficiently from an intrinsically low-mobility semiconductor.

Research Interest

Growth of thin oxide films and heterostructures by pulsed laser deposition Development of oxide photoelectrode materials for photocatalytic water splitting Polar oxides and multiferroic coupling Synthesis of nanostructures and nanocomposite thin films