Temperature Dependence of Inward Diffusion of Underpotentially-Deposited Cd into a Au (100) Bulk Phase under Electrochemical Environment

Abstract

We investigated the inward diffusion of underpotentially-deposited (UPD) Cd into a Au (100) substrate in 50 mol m À3 sulfuric acid solution under potential control by anodic voltammetry at the temperature range from 295 to 333 K, as well as by the electrochemical quartz crystal microbalance (EQCM) analysis and X-ray diffractmetry (XRD). The anodic voltammograms show that inward diffusion of the Cd adatoms into a Au (100) bulk phase is classified into two types of steps. One is a very fast step, which is the diffusion of UPD Cd into a Au (100) electrode at the surface layer; the activation energy of this step is ¼ $ 70 kJ mol À1 . The other is a much slower step; the activation energy of this step (110 kJ mol À1 ) agrees well with that of Cd bulk diffusion into a Au-Cd compound. The amount of UPD Cd is calculated from EQCM analysis, and it nearly agrees with that obtained from anodic voltammetry. We found that the amount of UPD Cd increases with temperature. We confirmed the formation of Au-Cd layer on the sample by XRD after maintained at the UPD region of À1100 mV vs. Hg/Hg 2 SO 4 for 1 h at 333 K.

Potential Pulse ALD for Room Temperature Fabrication of Stoichiometric CdTe Nanofilms

“…As the potential is scanned cathodically from open circuit potential (OCP: +300mV), a under potential deposition (UPD) feature of Cd is observed at from 100 mV to −200 mV (Figure 2A left inset; all potentials are referenced to 3M Ag/AgCl reference electrode). The application of potential more cathodic than −600 mV resulted in increase in deposition currents due to formation of Cd/Au alloy 34 The CV for a gold electrode in 0.2 mM TeO 2 , pH 2 solution is shown in Figure 2B. The UPD features of Te can be seen at 300mV and −100mV respectively (Figure 2B inset) with its corresponding anodic stripping peak appearing as small shoulder at 600mV during the reverse scan.…”