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. I n layers were constantly deposited at underpotential from acetic buffer sol utions, whereas As layers were obtained by three different approaches. Firs t, As-upd layers were obtained by reducing an excess of previously deposite d As(0) to AsH3 from NaOH solutions obtaining no more than five layers of I nAs. Secondly, As was deposited at underpotential from ammonia buffer solut ions 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 i n the reduced - III state, whereas most of it was in the oxidized + III sta te. The incomplete charge transfer in AsO2- reduction excludes the possibil ity of InAs formation. The effective way of depositing InAs on Ag(111) cons ists in depositing bulk As(0), limiting the extent of deposition through th e control of the time as well as the potential of deposition. Thus. As laye rs 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 classi cal methods of analysis. Both methods gave the 1:1 stoichiometric ratio, ty pical of a compound, though the extent of deposition seems to be low. Howev er, the AFM morphological investigation of samples obtained with 50, 75 and 100 deposition cycles point to a high quality compound. (C) 2001 Elsevier Science B.V. All rights reserved.