Photoresponse enhancement in SnO2-based ultraviolet photodetectors via coupling with surface plasmons of Ag particles

We report the photoresponse enhancement in an ultraviolet photodetector based on SnO2 with dipole-forbidden transition via Ag surface plasmon coupling. The SnO2:Ag film with Ag particles (SnO2:Ag/Ag composite film) was prepared using a sol-gel method and post-annealing technique. The interdigital Au electrodes were fabricated on the SnO2:Ag/Ag composite film using photolithography method to obtain the metal-semiconductor-metal (MSM) structured photodetectors. The response peak and cutoff wavelength of the device based on the SnO2:Ag/Ag composite film showed a significant redshift with respect to the pristine SnO2 photodetector. A fourfold enhancement in peak responsivity from the device based on SnO2:Ag/Ag composite film was observed by modifying film surface using Ag particles, which is ascribed to Ag surface plasmons coupling with SnO2 composite film. Finally, first-principles calculations indicated that Ag substituting Sn sites in SnO2 break the dipole-forbidden rule of SnO2 and result in the strong near-band-edge absorption. Our results suggest that the modification of Ag particles to SnO2 surface is a promising route to enhancing the performance of SnO2 ultraviolet photodetector.