ELECTROCHEMICAL DEPOSITION OF SILVER NANOCRYSTALLITES ON THE ATOMICALLY SMOOTH GRAPHITE BASAL-PLANE

A potentiostatic pulse method has been employed to electrochemically d eposit silver nanocrystallites on the atomically smooth graphite basal plane surface. Voltage pulses having amplitudes of 100, 250, and 500 mV vs Ag-0 and durations of 10 or 50 ms were applied to graphite surfa ces immersed in dilute (approximate to 1.0 mM) aqueous silver nitrate. During the deposition pulse, the current increased in approximate pro portion to (time)(1/2) as expected for an instantaneous nucleation and three-dimensional growth mode of deposition. Consistent with this gro wth mode, noncontact atomic force microscopy (NC-AFM) examination of g raphite surfaces following silver deposition revealed the existence of silver particles at a coverage of near 10(10) cm(-2) which were well- separated from one another on atomically smooth regions of the graphit e basal plane surface. These particles were disk-shaped having a heigh t of 15-50 Angstrom and an apparent diameter which varied from 200 to 600 Angstrom; particle dimensions increased smoothly with the coulomet ric loading, Q(Ag), over the interval from 0.31 to 36 mu uC cm(-2) and in approximate proportion to Q(Ag)(1/3). Significantly, silver nanocr ystallites present on the atomically smooth regions of a graphite surf ace could not be observed by using either the scanning tunneling micro scope (STM) or a conventional repulsive mode atomic force microscope ( AFM). In addition to NC-AFM, the characterization of these silver nano crystallites by transmission electron microscopy lattice imaging and A uger electron spectroscopy is reported.