Trap-Related Nonvolatile Negative Photoconductivity in a Single Ag@Al2O3 Hybrid Nanorod for a Photomemory with Light-Writing and Bias-Erasing

For zero band-gap metal Ag and ultrawide band-gap Al2O3, it is difficult to produce impressive photoresponse to visible light due to the limitation of energy gaps. Herein, it is demonstrated that individual Ag@Al2O3 hybrid nanorods, synthesized by a two-stage hydrothermal method and followed by thermal reduction annealing, can show excellent negative photoconduction of about 400 nm violet and 800 nm near-infrared lights at room temperature. Moreover, the light-induced high resistance state (HRS) is well maintained at relatively low operation bias after the removal of illumination, indicative of a nonvolatile memory effect. More importantly, the device is back to its initial low resistance state (LRS) after subsequently being applied a relatively large bias, suggestive of an erasable effect with large bias. In the hybrid nanorods, Ag nanoparticles serve as trap centers and can capture and store charges. Under the illumination of sub-band-gap light, trapped charges are excited, resulting in an HRS due to emptying the traps. On the contrary, a large external electric field triggers charges to be injected into traps in dark, resulting in an LRS. Regarding a superior negative photoswitching with light-writing and bias-erasing memory, Ag@Al2O3 nanohybrids have a tremendous potential in optical sensors and nonvolatile photomemory applications.