In-Situ and Ex-Situ Monitoring of Electrochemical Deposition of Silver Using Quartz Crystal Resonators

Abstract

Electrochemical deposition of silver from a 1 mM AgNO3 aqueous acidic solution at 20 μA cm−2 was monitored by means of in-situ quartz crystal impedance (QCI) technique, in-situ quartz crystal microbalance (QCM) technique, ex-situ QCI technique and atomic absorption spectroscopy. However, the mass evaluated from the data obtained in the in-situ QCI and QCM measurements on the basis of Sauerbrey equation deviated from intrinsic mass of the deposited silver because of a low deposition efficiency, liquid viscously or rigidly coupled with the resonator and/or stress generated in the deposited layer. Thus one must pay attention to these factors when one calibrates a quartz crystal microbalance on the basis of electrochemical deposition of a metal. In-situ QCI method utilizing a network analyzer is shown to be a powerful technique for simultaneous and qualitative monitoring of mass and surface structure changes. For the quantitative mass measurements, the mass sensitivity must be calibrated using another direct method such as atomic absorption spectroscopy.

Deposition and Dissolution of Copper on a Quartz Crystal Resonator in Contact with a Separator

“…The overestimation of the mass change has been widely reported during metal deposition. 2,12 The deviations from the theoretical value have often been explained by the roughness and the internal stress of the deposits. 1 An increase in the surface roughness leads to the mass gain due to inclusion of the electrolyte in the porous surface, resulting in the overestimation of the mass chnage.…”

“…1 An increase in the surface roughness leads to the mass gain due to inclusion of the electrolyte in the porous surface, resulting in the overestimation of the mass chnage. 1,2,12,17 Since the surface of the Pt EQCM electrode was covered with Cu particles with the diameter of less than 2 µm from the SEM observation as shown in Fig. 5, the roughness of the electrode surface was considered one of the factors of the overestimation.…”

“…The internal stress in the deposits is known to affect the resonance frequency. 1,2 The Stress-induced frequency shift is negative for an AT-cut resonator under the compressive stress, leading to the overestimation of the mass change. The residual stress in electrodeposited Cu film has been reported to depend on the substrate, grain size, growth rate, additives in the electrolyte, and so on.…”

“…Electrochemical quartz crystal microbalance (EQCM) technique can monitor the small change in the electrode mass during electrode reactions using a metal electrode formed on a quartz crystal resonator as a working electrode. 1,2 The change in the resonance frequency of an EQCM electrode, ¦f m , reflects the change in the electrode mass, ¦m, according to Saurbrey equation, 3 Áf m ¼ À…”