ELECTRIC-FIELD INDUCED PHASE-TRANSITIONS IN SCANNING TUNNELING MICROSCOPY EXPERIMENTS ON AU(111) SURFACES

Phase transitions of charged Au(111) surfaces during scanning tunneling microscopy imaging in air are reported. The reversible appearance and disappearance of corrugation line pairs of 0.2 angstrom height and approximately 63 angstrom periodic spacing as a function of the bias voltage is attributed to electric-field induced transitions of the surface layer between the 1 x 1 and the square-root 3 x 22 phases. The results indicate that the sign (positive or negative) of the electronic surface excess charge is the controlling factor in determining the relative stability of the two surface phases. The estimated excess charge threshold values for the appearance (approximately -1-mu-C/cm2) and lifting (approximately +3-mu-C/cm2) of the square-root 3 x 22 reconstruction features are compared to corresponding values obtained in electrochemical investigations.