Thickness, Surface Morphology, and Optical Properties of Porphyrin Multilayer Thin Films Assembled on Si(100) Using Copper(I)-Catalyzed Azide鈭扐lkyne Cycloaddition

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• 作者：Peter K. B. Palomaki ; Alexandra Krawicz ; Peter H. Dinolfo
• 刊名：Langmuir
• 出版年：2011
• 出版时间：April 19, 2011
• 年：2011
• 卷：27
• 期：8
• 页码：4613-4622
• 全文大小：1121K
• 年卷期：v.27,no.8(April 19, 2011)
• ISSN：1520-5827

文摘

We report the structure, optical properties and surface morphology of Si(100) supported molecular multilayers resulting from a layer-by-layer (LbL) fabrication method utilizing copper(I)-catalyzed azide鈭抋lkyne cycloaddition (CuAAC), also known as 鈥渃lick鈥?chemistry. Molecular based multilayer films comprised of 5,10,15,20-tetra(4-ethynylphenyl)porphyrinzinc(II) (<b>1b>) and either 1,3,5-tris(azidomethyl)benzene (<b>2b>) or 4,4鈥?diazido-2,2鈥?stilbenedisulfonic acid disodium salt (<b>3b>) as a linker layer, displayed linear growth properties up to 19 bilayers. With a high degree of linearity, specular X-ray reflectivity (XRR) measurements yield an average thickness of 1.87 nm/bilayer for multilayers of <b>1b> and <b>2b> and 2.41 nm/bilayer for multilayers of <b>1b> and <b>3b>. Surface roughnesses as determined by XRR data fitting were found to increase with the number of layers and generally were around 12% of the film thickness. Tapping mode AFM measurements confirm the continuous nature of the thin films with roughness values slightly larger than those determined from XRR. Spectroscopic ellipsometry measurements utilizing a Cauchy model mirror the XRR data for multilayer growth but with a slightly higher thickness per bilayer. Modeling of the ellipsometric data over the full visible region using an oscillator model produces an absorption profile closely resembling that of a multilayer grown on silica glass. Comparing intramolecular distances from DFT modeling with experimental film thicknesses, the average molecular growth angles were estimated between 40掳 and 70掳 with respect to the substrate surface depending on the bonding configuration.