Manipulating Surface Potentials of Metal Oxides Using Semiconductor Heterojunctions

Controlling the free-surface electrostatic potential of semiconducting metal oxides offers possibilities for improving the performance of sensors and catalysts and photocatalysts. However, methods to exert such control have typically proven to be inexact and unreliable. The present work demonstrates an approach based on semiconductor heterojunctions, wherein an oxide substrate with controlled carrier concentration supports a much thinner layer. The layer is too thin to absorb all the charge that would normally transfer, so some of the excess charge propagates to the free surface and changes the surface potential. A combination of standard heterojunction analysis via Poisson's equation and surface potential measurements verifies the workability of this concept for thin polycrystalline V₂O₅ grown on polycrystalline anatase TiO₂.