Grain Structures and Boundaries on Microcrystalline Copper Covered with an Octadecanethiol Monolayer Revealed by Sum Frequency Generation Microscopy.
An octadecanethiol (ODT) self-assembled monolayer on microcrystalline copper was investigated by sum frequency generation (SFG) imaging microscopy. The crystal grain and grain boundaries of the copper surface were mapped in the SFG image based on the strong brightness contrast of the SFG signal across the boundary. Local SFG spectra reveal significant difference with each other as well as the average SFG spectra, indicating the heterogeneity of the copper surface resulting from copper grains with distinct crystallographic facets and orientations. It is demonstrated that the SFG signal of crystalline domain areas contains azimuthal anisotropy with respect to the plane of incidence. In addition, the statistical orientation analyses of amplitude ratio of CH3-sym/CH3-asym and corresponding contour maps imply that the orientation of ODT molecules is affected by the underlying copper.
Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States.
Ming
M
Fang
Department of Chemistry, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, United States.
Steven
S
Baldelli
alkanethiol monolayers copper; corrosion; metal interface; molecular orientation; nonlinear imaging; self-assembled monolayers; vibrational spectroscopy