Time dependent, cathodic electrodeposition of ultrathin CdTe and Te films has been studied in 50 mM H2SO4 + 1 mM CdSO4 + 0.1 mM TeO2 solutions at room temperature under potential control using electrochemical atomic force microscopy (EC-AFM). The films were also characterized electrochemically and with X-ray diffraction. The growth mechanism and the composition of the films depends on the applied potentials. Island-like growth mode was observed for CdTe films when the deposition potential was -0.35 V (SHE). At a more positive deposition potential of 0.138 V (SHE), Cd was not codeposited into the film but affected the dynamic growth mode of the deposit. At this voltage smooth Te films were obtained. Depending on the applied potential, Cd acts either as a codeposition element for CdTe film growth, or as a mediator for layer-by-layer growth of Te films. (c) 2006 Elsevier Inc. All rights reserved.