AVS 51st International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM8
Field Emission from a Tungsten MEMS Structure

Tuesday, November 16, 2004, 10:40 am, Room 213C

Session: MEMS and NEMS: Enabling Tools for Scientific Research
Presenter: D. Cruz, UCLA/Sandia National Laboratories
Authors: D. Cruz, UCLA/Sandia National Laboratories
J.P. Chang, University of California, Los Angeles
M.G. Blain, Sandia National Laboratories
Correspondent: Click to Email
We have investigated the field emission properties of free-hanging tungsten MEMS structures. The structures act as electrodes for a Paul ion trap. The ion trap consists of two end cap electrodes, a ring electrode, and a detector, fabricated in seven layers of tungsten molded about SiO2 and then released to realize a free-hung structure. In this work, different ion trap sizes (inner ring electrode radius of 1 and 1.5um) and three different sized arrays (1e4, 1e5 and 1e6 traps) were fabricated and tested for field emission. To test whether field emission may be a problem during the operation of the ion trap, voltage was applied between the outer edge of one of the end caps and the inner edge of the ring electrode. Since electrode separations are on the order of 0.5um and electrode edges are sharp, field emission may occur if a suitably large potential difference is applied. The arrays were tested at atmospheric pressure and under vacuum, 1e-6 torr. The atmospheric tests showed turn-on voltages of 150V for the 1 and 1.5um traps. Currents of 3uA were achieved for the 1um trap 1e6 array at 300V. The vacuum tests showed turn-on voltages of 200V, and lower currents at 300V for the 1um trap array. The current-voltage responses were fitted well to the Fowler-Nordheim characteristics, confirming the field emission from the devices. The difference in current between the test conditions, however, suggests a breakdown discharge at atmosphere pressures. A stable emission was obtained at 300V for 5 min. in vacuum for the 1um trap 1e6 array. The measurements show that field emission will not be an issue for operation of the traps at the required rf amplitudes; however, the results suggest an interesting alternative application for such structures as field emission devices. *Sandia is a Multiprogram Laboratory Operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000