A novel approach to measure the step line tension and the step dipole moment on vicinal Au(0 0 1) electrodes

• Published in: Surface science Vol. 601; no. 8; pp. 1876 - 1885
• Main Authors: Beltramo, G.L., Ibach, H., Giesen, M.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2007; Amsterdam Elsevier Science; New York, NY
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electrolyte; Exact sciences and technology; Physics; Potential of zero charge; Step dipole moment; Step line tension; Stepped electrodes; STM; Vicinal; Step line tension; Au; Electrolyte; Step dipole moment; Vicinal; Potential of zero charge; Stepped electrodes; STM; Scanning tunneling microscopy; Au(OO1); Dipole moments; Step
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2007.02.012

In this paper we introduce a new experimental approach to determine the potential dependence of the step line tension on metal electrodes in contact with an electrolyte: (0 0 1) and (1 1 n) surfaces of single crystal gold electrodes were investigated by impedance spectroscopy in solutions containing weakly adsorbing anions, such as ClO 4 - , F − and SO 4 2 - . Within the limits of error the shift in the potential of zero charge is proportional to the step density of the vicinal surfaces indicative of a well-defined dipole moment per step length. The dipole moments per step atom are 6.8 ± 0.8, 5.2 ± 0.4, 5.8 ± 0.5 × 10 −3 eÅ for SO 4 2 - , ClO 4 - , and F − containing electrolytes, respectively. Using the values for the pzc and the potential dependence of the capacitance curves, the potential dependence of the surface tension of the vicinal surfaces is determined. The line tension of the steps is then calculated from the difference between the surface tension of the stepped and the step free surface. Our results represent the first experimental confirmation of a recent theoretical model proposing that in absence of specifically adsorbed ions the step line tension should decrease (roughly linear) with potential.