Methods for extracting or harvesting energy from the surrounding battlefield environment are of great importance to the United States Army. Scavenging energy from local environments reduces the required energy and weight transported to the theater. Micro- and nano-scale metal-insulator-metal (MIM) tunnel diodes are being developed to provide half-wave rectification as part of a “rectenna” energy harvesting system, which includes a radiation-collecting antenna, a rectifying MIM tunnel diode, and a storage capacitor. In this work, high-frequency MIM tunnel diodes for power rectification were designed, fabricated and characterized. Planar Pt/TiO2/Ti stacks are being fabricated to create a diode with highly asymmetric I-V characteristics that has a very low threshold voltage. The metals were chosen for their high work function difference, and the insulator was chosen for its barrier height, its compatibility with Ti, and its availability. The energy band diagram and the I-V characteristics were modeled to determine the feasibility of the Pt/TiO2/Ti material system for use as a rectifier diode in a rectenna system. Metals and insulator thin films were deposited onto silicon dioxide/silicon substrates. Pillars with lateral dimensions ranging from 20 μm x 20 μm up to 100 μm x 100 μm were fabricated. The dielectric thickness of the MIM diode was varied from 5 nm up to 50 nm to determine the optimal thickness for quantum tunneling. I-V measurements were taken using an electrical characterization system to confirm a non-linear, asymmetric response on a survey of devices fabricated with varying areas. Preliminary results exhibit asymmetric I-V characteristics with threshold voltages of less than 700 mV.