High photocurrent gain in SnO2 nanowires

Huge photocurrent gains with a value of $10000$ detected in air and $100000$ detected in vacuum have been obtained from ${\text{SnO}}_2$ 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.