In order to obtain information about the process of crystal formation and growth, a variety of in-situ and ex-situ methods, such as chronoamperometry, impedance spectroscopy, reflectance electron microscopy (REM), or transmission electron microscopy (TEM), has been used. A great step forward was the application of in-situ scanning tunneling microscopy, STM, to observe the surface during the growth process (see other chapters in this book). Recently we pointed out the possibility of using surface-enhanced Raman spectroscopy (SERS) as a sensitive tool for in-situ monitoring of electrochemical deposition.

One can follow the electrodeposition of SER-active metals by the development of vibrational bands of the surface-active components. Using chronocoulometry and semiempirical theories of nucleation it is possible to determine the kinetic parameters of nucleation and to compare this information about micro- and submicrostructures of a growing surface layer with the Raman intensities. This comparison shows that the SERS intensity is related to the surface structure. The method has been further developed for in-situ monitoring of electrocrystallization, mainly of silver [1],

Using the double-pulse method for the electrodeposition process [2], the kwon SERS signal of adsorbed cyanide ions at 2110 cm"1 showed a splitting into different bands; first results were reported in [3]. A tentative explanation was given by the assumption of formation of different sizes of clusters with different SER frequencies of the adsorbed ions.

In this report we show in more detail correlation between the intensity of the Raman signal and the developing surface morphology. We show SER spectra of adsorbted cyanide ions during the electrocrystallization and crystal growth in comparison with in-situ capacity measurements representing the „true area" of a growing surface. Furthermore, we present more results of the observed splitting of the CN" band on an Ag surface and discuss in greater detail the explanation of this splitting. The purpose of this contribution to the monograph is to give an example of the way in which other methods such as surface-enhanced Raman spectroscopy might complement the results of STM in studying the electrocrystallization process. In-situ surface-enhanced Raman spectroscopy was chosen because it adds the power of vibrational spectrscopy to the geometrical results of STM.

0 0

Post a comment