Plasmonic Photoresistor Based on Interconnected Metal-Semiconductor Grating

Metal-semiconductor nanostructures in various configurations are extensively used in photodetection, photocatalysis, and photovoltaics. For photodetection purposes, the working principle is straightforward; on illumination, generated charge carriers in excess lead to a decrease in resistance. Notably, using an interconnected metal-semiconductor grating, it is observed and now reported an opposite response, an increase in the resistance. Such photoresistors are fabricated through wrinkle structuring and oblique angle material deposition methods. It is found that the controlled wrinkling leads to large-area 1D periodic structures with coexisting cracking perpendicular to the grating direction-such cracks are used as connections between the two-point contact measurement through the associated gold layer deposition. An enhanced current reduction is further observed on photoexcitation for an additional deposition of an amorphous titania layer. Subsequently, a discussion on the mechanisms and interaction between hot electron injection, charge carrier recombination, and thermalization is presented. Supported by numerical modeling, the angle-resolved plasmonic modes with the photoresistance can be correlated. The ease of layered deposition of the materials allows one to extend the studies on cavity-based structures with sandwiched titania layers as hotspots. This simple, scalable, and robust fabrication method thus promises an efficient routeway toward photosensor development in which plasmon-mediated hot electrons play a crucial role.

Automated summary

Metal-semiconductor nanostructures are widely used in photodetection, photocatalysis, and photovoltaics. In photodetection, the resistance typically decreases with the generation of charge carriers upon illumination, but an opposite response, an increase in resistance, is observed in interconnected metal-semiconductor gratings. This study presents a fabrication method using wrinkle structuring and oblique angle material deposition to create photoresistors with large-area periodic structures and cracks that serve as connections for two-point contact measurements. It is also found that an additional deposition of an amorphous titania layer further enhances the current reduction on photoexcitation.