4th INTERNATIONAL WORKSHOP ON ELECTRODEPOSITED NANOSTRUCTURES 16-18 March 2006, Dresden, Germany	ABSTRACTS

ELECTROCHEMICAL ATOMIC LAYER EPITAXY OF COMPOUND SEMICONDUCTORS ON COPPER SINGLE CRYSTALS R. Kowalik, F. Loglio, M. Innocenti and M.L. Foresti Department of Chemistry, University of Florence, Florence, Italy Electrochemical Atomic Layer Epitaxy (ECALE) was proposed by Stickney and coworkers to obtain low-cost production of structurally well-ordered II-VI compound semiconductors, such as cadmium and zinc chalcogenides, on polycrystalline as well as on single-crystal gold electrodes [1] and was recently extended to the (111) face of silver [2]. The method is based on the alternate underpotential deposition (upd) of atomic layers of the elements that form the compound. Underpotential deposition (upd) is the well-known phenomenon whereby the potential necessary to deposit one element onto a second element occurs before that necessary to deposit the element on itself. The phenomenon is surface limited, so that the resulting deposit is generally limited to one atomic layer. Moreover, when the upd is performed on a single crystal face the resulting deposit is epitaxial. The free energy change involved in the compound formation is generally negative enough to produce the underpotential deposition of the metallic element on a layer of the previously deposited non metallic element, and vice versa. The number of cycles, which determines the thickness of the deposits, can be repeated as many times as desired to obtain deposits of practical importance. By limiting depositions to single atomic layers, no three dimensional growth is promoted and epitaxy should result. Once the deposit is formed, the amount of the elements deposited is determined from the charge involved in their stripping. Such investigations always confirmed the stoichiometric ratio of the elements forming the compound. The good characteristics of composition, structure and morphology of the deposits have been determined by means of surface techniques such as XPS, AFM, STM, SXRD. Then, photoelectrochemical measurements testify the good quality of the compounds obtained. Central to the method is the necessity of singling out the proper electrochemical conditions to be used, i.e. potentials, reactants, electrolytes and pH. Moreover, being the method based on surface phenomena, the electrochemical conditions are also dependent on the substrate used. In this respect, the use of silver or copper substrates in place of gold prevents the use of the positive range of potentials; on the other hand it could be advantageous in view of potential applications in the fabrication of devices. Here, the first results of the electrodeposition of ZnSe on Cu(111) are reported. REFERENCES (1) (a) Stickney, J.L. J. Electroanal. Chem.; 1991, 300, 543.; (b) J.L. Stickney, in A. J. Bard and I. Rubinstein (Editors), Electroanalytical Chemistry, Marcel Dekker, Inc, New York, Vol. 21,1999. (2) (a) M. Innocenti, G. Pezzatini, F. Forni and M.L. Foresti, J. Electrochem. Soc., 148(5)(2001)C357-C362; (b) F. Loglio, M. Innocenti, G. Pezzatini and M.L. Foresti, J. Electroanal. Chem., 562(2004) 117-125.

 
 
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