Metal-Insulator-Metal Point-Contact Diodes as a Rectifier for Rectenna

The rectenna (rectifying antenna), if extended to operate at visible light, will revolutionize the way sunlight is harvested for electricity. The focus of this work is to develop a suitable rectifier component of the rectenna for rectifying high-frequency radiation. In this work, a point-contact metal-insulator-metal (MIM) diode based on Nb-Nb₂O₅ and Nb-TiO₂ was fabricated and successfully tested at low frequency. Fabrication of point-contact MIM diodes was greatly simplified by adopting a facile fabrication approach. The ultra-thin (less than 5 nm) insulator layer was deposited via anodic oxidation (of the metal layer), a non-vacuum technique. The second metal is in the form of a bent wire and hence results in a point-contact diode area. An optimization study was carried out to deposit a smooth insulator film with the desired chemical composition. Although researched for more than six decades, suitable MIM devices for high-frequency rectification (with all the desired rectifier behavior) have not yet been developed, mainly because of the many technical difficulties involved. One such difficulty is the lack of optimization of material properties of MIM structures. A systematic study to fill in this lack of knowledge that relates material properties to MIM device performance is reported here. Based on this systematic study, we find a strong correlation between the work function and electron affinity of the metal and insulator, respectively, on MIM device performance.