Regensburg 2004 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 16: POSTER: Computational Physics, Complex Systems
CPP 16.22: Poster
Tuesday, March 9, 2004, 17:00–19:00, B
Roughness-Induced Acoustic Second Harmonic Generation (ASHG) During Electrochemical Metal Deposition on the Quartz Crystal Microbalance — •Katrin Wondraczek1, Susanne Wehner2, Andreas Bund2, and Diethelm Johannsmann1 — 1Institut fuer Physikalische Chemie, TU Clausthal, Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld — 2Institut fuer Physikalische Chemie und Elektrochemie, TU Dresden, Mommsenstrasse 13, D-01062 Dresden
When operating a quartz crystal with a rough surface in liquids, there is an emission of shear and compressional waves at twice the frequency of the exciting wave (acoustic second harmonic generation, ASHG). We used electrochemically deposited copper layers whose roughnesses could be tuned via current density.
Roughness is a source of ASHG if the liquid flow at the surface is not entirely laminar. The calculation of the Reynolds number shows that slight deviations from laminar flow can be reached at high amplitudes of shear oscillation. However, nonlinear effects in the operation of the QCM in liquids are small.
Our experiments show that a rough surface is much more efficient in generating acoustic second harmonic waves than a smooth one. We present a model that relates ASHG to a roughness parameter independently obtained from resonance frequency and bandwidth. Such a parameter allows to distinguish the effects of trapped liquid and hydrodynamics on rough surfaces from the effects of deposited mass.