Simultaneous Monitoring and Evaluation of Current and Mass Transients with the QCMB in the Millisecond Range

Abstract

An experimental set-up is described which allows the simultaneous recording of current and mass transients with millisecond resolution by using 5 MHz quartz resonators operated in a liquid environment. At the same time a mass resolution of a few nanograms is realized. It is demonstrated that this set-up allows the application of fast potential pulses to electrochemically depositastrip copper adlayers. The results proved that the obtained frequency response of the QCMB of 1 ms due to a sudden mass change has to be regarded as an upper limit and is independent on the type of oscillator circuit used. Thus, this technique allows monitoring and evaluation of fast electrode processes such as copper depositionastripping by comparing current and mass transients recorded simultaneously. With this technique the integral sensitivity E i for quartz resonators contacted with one face to a liquid was reinvestigated on the basis of charge and frequency changes associated with absolute mass changes spanning from the monolayer regime up to more than one hundred atomic layers. An unexpected sensitivity drop is observed in the lower monolayer regime which is related to interfacial processes that occur due to shear elongations at the phase boundary solidaliquid.

Study of the Electrodeposition of Rhodium on Polycrystalline Gold Electrodes by Quartz Microbalance and Voltammetric Techniques

“…The advantage of the combined use of massograms and voltammograms for the study of different types of electrochemical reactions was illustrated recently by several authors. [14][15][16] It is shown that the nucleation and growth of rhodium on polycrystalline gold from concentrated chloride solutions is a typical example of the effect of slow electrode kinetics on the morphology of potentiostatic transients.…”