| We have constructed a surface second harmonic imaging system capable of acquiring spatially-resolved surface second harmonic data with diffraction-limited resolution. For a 100x magnification microscope objective of numerical aperture 0.55, we achieve a resolution of ∼0.5mum. We have used surface second harmonic imaging measurements to characterize the heterogeneous structure of organic compounds bound to silica substrates using zirconium bisphosphonate chemistry. Previous second harmonic generation intensity measurements of these surfaces have revealed multiple domains, but it was not possible to elucidate the characteristic domain sizes.; The images acquired for a series of silica surfaces modified with controlled amounts of a rigid chi(2) chromophore reveal the presence of two domains, with characteristic sizes of ∼1mum and ∼15mum, and with the relative contribution of each domain changing with the composition of the imaged monolayer. To extract this information from the experimental surface second harmonic images, we have applied a correlation-based analysis and provide a detailed description of this methodology in Chapter 2. The presence of multiple domains underscores the heterogeneous nature of silica surfaces and the need for spatially resolved information to characterize the heterogeneity.; We have also fabricated two multilayer assemblies of the nonlinear chromophores (4-(4-(4-(4-((2-Hydroxyethyl) sulfonyl) phenyl) piperazinyl)-phenyl) phosphonic acid (C1) and (2-(4-(4-(4-(4-hydroxyphenyl)piperazinyl)phenyl)azophenyl)sulfonyl) ethylphosphonic acid (C2). The C1 multilayer assembly exhibits a decreasing degree of correlation as the number of deposited layers increases. In the context of island like deposition of ZP films this result is reasonable since small islands are less likely to be correlated and begin to resemble a randomized surface. Average feature sizes calculated for the C1 sample were ∼11mum, in reasonable agreement with the larger feature size observed in the monolayer experiments of chapter three (∼15mum). The C2 multilayer assembly produced feature sizes of ∼10mum, also in fair agreement with the monolayer results. In contrast with the C1 assembly, however, no decrease in correlation was observed with increasing number of layers. The absence of a similar trend to the C1 sample was unexpected considering the similarity in structure between C1 and C2. |
