Antenna-coupled metal-insulator-metal rectifier
The use of rectennas, or antenna-coupled rectifiers, using metal-insulator-metal tunnel diodes as rectifiers for energy conversion has been explored with more fervor recently, given the advances in nanotechnology fabrication and increased resolution of features. Some have made these devices from symmetric metals (e.g. Ni—NiO—Ni) and asymmetric metals (e.g. Al—AlOx/Pt), and have used deposited oxides as well as native oxides. One key to obtaining a highly asymmetric device with efficient current generation needed for high conversion efficiency is to instead use dissimilar metals and a thin reproducible oxide. The described method allows for a thin, reproducible native oxide of nickel be integrated with any antenna metal to overcome oxide surface roughness problems that typically hamper the practicality of these devices.
1. A native nickel oxide process comprising:
depositing a first metal layer on a substrate;
depositing an Ni layer on the first metal layer;
patterning the Ni layer and first metal layer to define a first triangular bowtie radiating element having a base and an apex;
subsequently oxidizing the Ni layer with reactive ion etching the Ni layer in an oxygen plasma to produce an oxidized Ni layer; and
depositing a top layer of a second metal different from the first metal, to form a second radiating element of a bowtie antenna on the oxidized Ni layer, the top layer only partially overlapping the oxidized Ni layer near the apex of the triangular shaped radiating element.
2. The process of claim 1 wherein the first metal is aluminum (Al) and the second metal is platinum (Pt).
3. The process of claim 1 further comprising:
patterning the top layer to further define the second radiating element of the bowtie antenna, as a triangular radiating element having an apex overlapping the apex of the first triangular radiating element.
4. The process of claim 3 further wherein the step of patterning the Ni and first metal layers also forms a first arm adjacent the first triangular radiating element, and additionally comprising:
etching a portion of the oxidized Ni layer adjacent the arm; and
depositing a first conductive pad adjacent the first arm.
5. The process of claim 1 wherein the deposited Ni layer is between 5 and 20 nanometers (nm) in thickness.
6. The process of claim 4 wherein the step of depositing a top layer also forms a second arm adjacent the second radiating element, and further comprising:
depositing a second conduction pad adjacent the second arm.