EC-STM studies of Te and CdTe atomic layer formation from a basic Te solution
The cyclic voltammetry of Te on Au is markedly affected by pH. This fact can be used to advantage when designing an electrodeposition cycle for CdTe. For instance, if a pH 2 Te solution is used, the underpotential deposition (UPD) potential for Te is 0.8 V positive of that for Cd. However, if a pH 9.2 Te deposition solution is used, the potential for Te UPD coincides with that for Cd, greatly simplifying the development of an electrochemical atomic layer epitaxy (EC-ALE) cycle. This report describes electrochemical scanning tunneling microscopy (EC-STM) studies of Te deposition on Au(111) and Au(100) from basic media. Several structures were observed on Au(111): a (6 x 6) tellurite adlayer which spontaneously adsorbed prior to Te formation, a 1/4 coverage (2 x 2)-Te, and a 1/3 coverage (2 x root10)-Te. While on Au(111), a 1/3 coverage (root3 x root3)-Te with (13 x 13) light domain walls, and two (3 x 3)-Te structures, with coverages of 4/9 and 5/9, were observed. Results of the formation of the first CdTe compound monolayer using an EC-ALE cycle which includes Te deposition from a basic solution are also included. (C) 2004 The Electrochemical Society.