New real-time analytical applications of electrochemical quartz crystal microbalance: Stoichiometry and phase composition monitoring of electrodeposited thin chalcogenide films

The electrochemical quartz crystal microbalance (EQCM) has recently gained increasing popularity as a powerful tool for electrochemical interface examinations. This paper reports on its great potential for developing new real-time analytical protocols. Potentiostatic coulometry is used in conjunction with quartz crystal microgravimetry (QCMg) with controlled hydrodynamics to develop two new analytical procedures: real-time stoichiometry monitoring of electrodeposited binary chalcogenide films and phase composition quantification of electrodeposited ternary chalcogenide compounds. The newly developed EQCM methods are illustrated on the examples of Ag2+δSe-electrodeposited films and the electroformation of ternary CuAgSe-films. Both compounds have been successfully used as ion-selective membranes for flow-injection detectors. The experimental set-up including hydrodynamic control, the main strategy of the approach used and its scope and limitations are broadly discussed. The obtained data allow for real time profile monitoring of either stoichiometry (Ag2+δSe-case) or phase composition (CuAgSe-case).