A comparative study of the metal/electrolyte and metal/vacuum interfaces: Optical second harmonic measurements of the noble metal Ag(111), Cu(111), and Au(111) surfaces

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7112237

Bradley, Jr, R A

Presented in this dissertation is a series of second harmonic generation (SHG) experiments on the single crystal Ag(111), Cu(111) and Au(111) surfaces. These studies exploit the inherent surface sensitivity of this nonlinear optical technique to study surface electronic structure, surface oxidation, and surface reconstructions. Another advantage of the SH technique is the ability to make comparative measurements in ultra high vacuum (UHV) and in an electrolyte solution. Reported are measurements of the second harmonic response from these surfaces in the electrochemical environment and in UHV. The comparative wavelength dependent SH studies of the Ag(111) surface show that if the electrode is biased at the potential of zero charge (PZC), all of the surface properties correlate well with the properties of the Ag(111) surface measured in UHV. A resonance feature is observed in the wavelength dependence (2[omega] = 300-350 nm) of the SH response. This resonance feature is assigned to known surface electronic structure of Ag(111) in UHV and exhibits sensitivity to the applied potential. A simple model is presented incorporating the change in applied potential to account for the observed potential dependence of the resonance feature. The Au(111) surface is known to reconstruct in UHV and in the electrochemical environment. The SH results presented exploit the azimuthal dependence of the response to probe symmetry changes effected by this reconstruction. In UHV the SH response from the Au(111) surface also exhibits the symmetry of the unreconstructed surface. The comparative measurements of the SH response from Cu(111) reveal that the electrode surface, at all bias potential, is very different than in UHV. In contrast to the rotational anisotropy observed under 1064 nm excitation when the electrode is biased at the PZC, with 532 nm excitation the SH response is isotropic. Exposing the surface in UHV to oxygen changes the SH response at both wavelengths dramatically.

• Research Organization: Oregon Univ., Eugene, OR (United States)
• OSTI ID: 7112237
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
665000* -- Physics of Condensed Matter-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHEMISTRY
COPPER
ELECTROCHEMISTRY
ELECTROLYTES
ELEMENTS
FREQUENCY MIXING
GOLD
HARMONIC GENERATION
INTERFACES
METALS
NONLINEAR OPTICS
OPTICS
PLATINUM METALS
PRESSURE DEPENDENCE
SILVER
SURFACE PROPERTIES
TRANSITION ELEMENTS
ULTRAHIGH VACUUM