Bioscience (Nanotechnology): USRA Researchers Develop Vacuum Diode

April 2021

The Nanotechnology team consisting of Jin-Woo Han, Ph.D., Senior Scientist (USRA), Myeong-Lok Seol, Ph.D., Associate Scientist (USRA). has worked to fabricate a vacuum diode. This structure features nearly zero gate leakage current, thus overcoming a common problem in miniaturized vacuum electronics devices. This silicon based architecture could be readily fabricated on a wafer scale using a standard integrated circuit manufacturing process as demonstrated here. The results of this research were published in a recent issue of the journal Nanoscale Advances (vol. 3, pp. 1725-1729, 2021). This work was sponsored by the Space Mission Directorate (SMD), which strives to provide a ground technology for Europa exploration. 

Background: as part of this research, nanoscale field emission vacuum channel gated diode structure is proposed and a tungsten cathode with an umbrella-like geometry and sharp vertical edge is fabricated. The edge of the suspended cathode becomes the field emission surface. Unlike in the traditional transistor with the gate typically located between the source and the drain, the bottom silicon plate becomes the gate here and the anode terminal is located between the umbrella cathode and the gate. The fabricated devices show excellent diode characteristics and the gated diode structure is attractive for extremely low gate leakage.