Field-Dipole Interactions at p-GaAs (100) Electrode in Sodium Dodecyl Sulfate Acid Solution

Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used to investigate the effects of the sodium dodecyl sulfate (SDS) at the electrified p-GaAs(100) / H₂SO₄ interface. The analysis of the EIS data revealed that the surfactant adsorption brings about a pronounced decrease of the capacitive contributions of the semiconductor surface state (Fig. 1 B) accompanied by a shift to more positive potentials of the Mott-Schottky plot (Fig. 1 A). According to the XPS (Fig 1 C) and AFM data, SDS forms a well-ordered protective overlayer on p-GaAs(100) which prevents the surface oxidation in air. However, the field-dipole interactions acting under the applied potential control become preponderant at the electrified GaAs / solution interface yielding distinct effects at the end of the direct and forward potential scans as seen in Fig 1 C. These results suggest that SDS interaction with GaAs substrate might be an efficient tool to improve both the electronic properties of the semiconductor and its protection against the surface oxidation in air.

Acknowledgements

This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-ID-PCE-2011-3-0304