Chemisorption of 4-(4-amino-phenylazo) benzoic acid molecule on the Si(0 0 1)-(4 × 2) surface |
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Authors: | G Birlik G Demirel T Çaykara |
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Institution: | a Department of Chemistry, Gazi University, 06500 Ankara, Turkey b Department of Physics, Gazi University, 06500 Ankara, Turkey |
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Abstract: | Structural and electronic properties of self-assembled monolayer with 4-(4-amino-phenylazo) benzoic acid (APABA) on the Si(0 0 1)-(4 × 2) surface are investigated by ab initio calculation based on density functional theory. For the APABA chemisorption on the silicon surface, we have assumed two different binding sites: (i) amino group of molecule and (ii) carboxyl group of molecule. Considering amino-site, we have assumed two possible models for the chemisorption of molecules on the Si(0 0 1)-(4 × 2) surface: (i) an intrarow position between two neighboring Si dimers in the same dimer row (Model I), (ii) on-dimer position (Model II). We have found that Model II is 1.10 eV energetically more favorable than Model I. The Si-N bond length was calculated as 1.85 Å which is in excellent agreement with the sum of the corresponding covalent radii of 1.87 Å. Considering carboxyl-site, we have assumed exactly the same model as mentioned above. Again we have found that Model II is energetically favorable than Model I. The calculated bond lengths for Si-O and O-C are 1.76 and 1.35 Å, respectively. |
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Keywords: | Density functional theory Low index surface Si surface reconstruction Chemisorption Self-assembled monolayer Photoswitch molecules |
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