Electrochemical behavior of As on silver single crystals and experimental conditions for InAs growth by ECALE

Different experimental conditions for InAs growth by ECALE were examined. In layers were constantly deposited at underpotential from acetic buffer solutions, whereas As layers were obtained by three different approaches. First, Asupd layers were obtained by reducing an excess of previously deposited As(0) to AsH3 from NaOH solutions obtaining no more than five layers of InAs. Secondly, As was deposited at underpotential from ammonia buffer solutions of pH 9.6; at this pH the upd of both In and As coincide. However, XPS analysis on a sample revealed that only a low percentage, 25%, of As was in the reduced −III state, whereas most of it was in the oxidized +III state. The incomplete charge transfer in AsO2− reduction excludes the possibility of InAs formation. The effective way of depositing InAs on Ag(111) consists in depositing bulk As(0), limiting the extent of deposition through the control of the time as well as the potential of deposition. Thus, As layers were obtained from acetic buffer solutions at −0.7 V. The composition of samples prepared by this procedure was determined by XPS and by the classical methods of analysis. Both methods gave the 1:1 stoichiometric ratio, typical of a compound, though the extent of deposition seems to be low. However, the AFM morphological investigation of samples obtained with 50, 75 and 100 deposition cycles point to a high quality compound.