OSU researchers continue to demonstrate why the university pulls in so much industry capital. In breakthrough work published in journal of Applied Physics letters, Professor John F. Conley of the Department of Electrical Engineering and Computer science and doctoral candidate Nasir Alimardani demonstrated a novel approach to diode design that may help future manufactures bypass traditional silicon, all while driving up speeds and lowering the costs of manufacture.
Their new design leverages the well-known phenomenon of quantum tunneling, where two metals are asymmetrically, (M-I-M) separated by an insulator causing the electron to “tunnel” through the insulator instead of traversing the distance.
The difference in their research is threefold. First, they created a bilayer of insulators between the two metals, M-IIM, to induce a kind of “step tunneling”, second they recognized that using Atomic Layer Deposition to continuously deposit high quality insulators and an atomically smooth bottom electrode led to a “well controlled mechanical quantum tunneling effect.”
According to Nasir, “The impact of roughness can be appreciated if it is remembered that tunneling probability depends exponentially on the electric field in the thin dielectric film.” In short, a rough bottom leads to an uncontrollable tunneling effect.
Third, they made use of non-traditional materials for their metals and insulator bilayers. They used a composite metal, ZrCuAlNi(Zirconium, Copper, Aluminum, and Nickel) for the bottom electrode, nanolaminate insulator bilayers of Hafnium oxide and Aluminum oxide for the insulators, and evaporated Aluminum for the top electrode.
One of the hurdles to leveraging this phenomenon is that electrons will on occasion tunnel to somewhere they aren’t supposed to be, and in the electronics world misplaced electrons wreak all sorts of havoc on the system, often causing the system to short out, lose efficiency, or overheat.
Their method would enable future manufactures to finely control when, where, and how a given electron tunneled via changing the distance between or geometry of the bilayers. That control in turn might enable advances in “high speed applications such as infrared detectors, optical rectennas for IR energy harvesting and hot electron transistors, as well as for macroelectronic applications such as backplanes for LCDs.”
The optical rectenna is one of the most interesting potential avenues for this technology. Simply put, a rectenna is a special kind of antenna that allows for the conversion of one type of energy into direct current electricity. In this example it would allow for the conversion of solar energy, in the form of Infrared radiation or heat, into usable electricity. Forget bulky solar panel calculators from the 70s, imagine an IR powered phone that literally generates power from the ambient heat from your body or the environment.
By William Tatum