The Effect of Rotatable Ethynyls on the Monolayer Structure of a Biaxial Biphenyl(ethynyl)benzene: an STM/STS Study
Date Issued
2014
Date
2014
Author(s)
Wu, Hung-Jen
Abstract
This thesis reports the electronic communications between edge-on biphenyl moieties of biaxial TBPB (1,2,4,5-tetrakis-(4-dodecyl-4''- ethynyl-biphenyl)-benzene) by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Assemblies were realized by taking the advantages of the rotatable ethynyl linkers of the TBPB. Rotatable ethynyl linkers allowed the biphenyl moieties of the TBPB to adopt both face-on and edge-on orientations. We compared the difference of arrangements and electronic properties of TBPB under two concentrations, 0.32 mM and 3.2 microM. Topographic images revealed two kinds of concentrations, 0.32 mM and 3.2 microM., respectively, linear and mesh. Linear motif showed face-on and edge-on orientations because of different heights between biphenyls of TBPB in section profiles. Mesh motif showed only face-on orientation because of the same height of biphenyls of TBPB in section profiles. I–V curves of both motifs are asymmetric with respect to current at zero bias. The asymmetric feature was more significant for the linear motif than the mesh one, resulting in a larger tunneling current and a smaller turn-on voltage for the former. Linear motif were more conductive since edge-on orientations produce an effective electronic coupling between π-stacked biphenyls. Thereby, edge-on biphenyl moieties of biaxial molecule TBPB is the key to the successful assembly of conjugated 1D nanowires.
Subjects
掃描穿隧顯微術
掃描穿隧能譜
平躺位向
立起位向
電荷轉移
奈米導線
Type
thesis
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