High photocurrent gain in SnO2 nanowires

Huge photocurrent gains with a value of 10 000 detected in air and 100 000 detected in vacuum have been obtained from SnO2 nanowires. Unlike previous reports that emphasized on carrier trapping by charge oxygen molecules in metal oxide nanostructures, we point out that spatial separation of photoexcited electrons and holes due to built-in electric field induced by surface charge defects does plays a significant role especially for nanostructured materials with a large surface-to-volume ratio. The study shown here provides a useful guideline to achieve photodetectors based on nanostructured materials with high sensitivity.