AVS 46th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM+NS-WeM

Paper EM+NS-WeM11
Capacitance Measurements on Gold Nanowires

Wednesday, October 27, 1999, 11:40 am, Room 6C

Session: Nano-characterization of Molecules, Materials, and Devices
Presenter: A. Wlasenko, McGill University, Canada
Correspondent: Click to Email
There are several assumptions made about classical capacitors (C=Q/V): the density of states(DOS) of the plates is infinite, the potential drop occurs entirely across the plates, electrons don't interact, and there is no tunnelling. In mesoscopic capacitors, the voltage drop doesn't occur entirely across the plates, and the finite DOS plays an important role. In the experimental setup presented, the voltage-dependence of C is measured for gold nanowires allowing the DOS to be deduced according to theory [H. Guo et al., APL 74, 2887-2889 (1999)]. A piezotube is used to retract a gold sample in contact with a gold tip to form a nanowire. Along with measurements of C, simultaneous measurements of conductance(G) are made with a current preamplifier to monitor the transmission properties of the contact. Changes in the C of this nanowire are measured by a modified RCA Video Disc sensor: a resonant circuit is connected to a 915 MHz oscillator, and the amplitude of the signal is measured. A change in C leads to a shift in the resonance peak which is detected by the sensor. The sensor is calibrated using a ball bearing and metal plane geometry in comparison with classical calculations. The sensor is sensitive to C changes as low as 10@super -17@ F. When the tip and sample are in contact, the sensor measures a convolution of C and G. Where a variation in C leads to a shift in the resonance peak, a variation in G leads to a change of the FWHM. Measurements on either side of the resonance peak can be made in order to seperate C and G.