Atomic force microscopy of Au deposition from aqueous HF onto Si(111)

Non-contact atomic force microscopy (AFM) was employed following emersion to examine Au nanoclusters deposited from aqueous mixtures of HF and 10(-4) M KAu(CN)(2) onto Si(111). As the HF concentration is increased, the growth rates both parallel and perpendicular to the substrate of the approximately oblate Au hemispheroids increase. AFM images were obtained for times at which previously reported in situ second harmonic generation signals from the interface reach a maximum. At the time when the second harmonic enhancement is maximized during deposition from 0.500 (5.00)M HF, the Au nanoclusters have an average diameter of 94 (109) nm and an average height of 3.6 (9.5) nm. These cluster diameters can be understood qualitatively by the shift of the plasmon resonance due to depolarization as the cluster size increases, causing the resonant second harmonic enhancement at 532 nm to pass through a maximum at cluster diameters in the range 90-110 nm. (C) 1999 Published by Elsevier Science B.V. All rights reserved.