AVS 45th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM7
Current-Voltage Measurements of Ultrathin Metal-Si(111) Sensors

Wednesday, November 4, 1998, 10:20 am, Room 308

Session: Physics of Semiconductors
Presenter: H. Nienhaus, University of California, Santa Barbara
Authors: H. Nienhaus, University of California, Santa Barbara
H.S. Bergh, University of California, Santa Barbara
B. Gergen, University of California, Santa Barbara
A. Majumdar, University of California, Berkeley
E.W. McFarland, University of California, Santa Barbara
W.H. Weinberg, University of California, Santa Barbara
Correspondent: Click to Email
A novel microfabricated Si-based device structure was developed in order to characterize the transport properties of thin metal films on Si(111) ranging from 10 Å to 150 Å. Metals were evaporated onto the device under ultrahigh vacuum conditions. The evaporation temperature was varied between 130 and 180 K. The design of the device allowed zero-force electrical contacts to the very thin metal films on silicon for current-voltage (I/V) measurements. The resulting I/V curves were analysed within the thermionic emission theory. The change of Schottky-barrier height, ideality factor and serial resistance was monitored as a function of film thickness and temperature. Cu, Ag and Fe films were investigated on Si(111). Generally, an improvement of the rectifying properties was observed with increasing thickness. To study the temperature dependence, Cu films of about 60 Å were annealed to room temperature. This treatment led to a significant increase of the barrier height from 0.45 to 0.65 eV and a decrease of the ideality factor from about 2.5 to values close to 1. Subsequent cooling of the annealed samples conserved the excellent rectifying properties. This finding indicates that annealing of low-temperature deposited films reduces the inhomogeneity of the contact barrier height. Further evaporation of Cu onto annealed diodes led again to lower barrier heights and larger ideality factors. First results suggest that the devices are suitable sensors for detecting hot charge carriers created by gas-surface reactions.