Biomedical subjects

Natalie Stutzmann

Publications and source records attributed to Natalie Stutzmann.

4 recordsLinked to original sources

PubMed2006

Control of ambipolar thin film architectures by co-self-assembling oligo(p-phenylenevinylene)s and perylene bisimides.

Control of thin film morphology by self-assembly of, respectively, p-type oligo(p-phenylenevinylene)s (OPV)s and n-type perylenebisimides (PBI)s in solution prior to processing, results in film architectures consisting of uniform rodlike domains as shown by atomic force microscopy. Such films from self-assembled molecules show superior charge-carrier mobility in comparison with films processed from molecular dissolved molecules. Moreover, connecting the OPV and PBI building blocks through hydrogen-bonding interactions creates dyad complexes that cofacially stack in apolar solvents. Ambipolar field-effect transistors constructed from these dyad complexes show two independent pathways for charge transport. In strong contrast, processing of OPV and PBI, that are not connected by hydrogen bonds, form charge transfer donor-acceptor complexes that show no mobility in field-effect transistors presumably due to an unfavorable supramolecular organization.

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PubMed2005

High anisotropy of the field-effect transistor mobility in magnetically aligned discotic liquid-crystalline semiconductors.

A magnetic field has been utilized for producing highly oriented films of a substituted hexabenzocoronene (HBC). Optical microscopy studies revealed large area HBC monodomains that covered the entire film, while wide-angle X-ray measurements showed that the HBC molecules are aligned with their planes along the applied field. On the basis of this method, solution-processed field-effect transistors (FET) have been constructed with charge carrier mobilities of up to 10(-3) cm2/V.s, which are significantly enhanced with respect to the unaligned material. Exceptionally high mobility anisotropies of 25-75 for current flow parallel and perpendicular to the alignment direction have been measured as a function of the channel length. Atomic force microscopy performed on the FET structures reveals fibril superstructures that are oriented perpendicularly to the magnetic field direction, consisting of molecular columns with a slippage angle of 40 degrees between the molecules. For channel lengths larger than 2.5 mum, the fibrils are smaller than the electrode spacing, which adversely affects the device performance.

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PubMed2003

Self-aligned, vertical-channel, polymer field-effect transistors.

The manufacture of high-performance, conjugated polymer transistor circuits on flexible plastic substrates requires patterning techniques that are capable of defining critical features with submicrometer resolution. We used solid-state embossing to produce polymer field-effect transistors with submicrometer critical features in planar and vertical configurations. Embossing is used for the controlled microcutting of vertical sidewalls into polymer multilayer structures without smearing. Vertical-channel polymer field-effect transistors on flexible poly(ethylene terephthalate) substrates were fabricated, in which the critical channel length of 0.7 to 0.9 micrometers was defined by the thickness of a spin-coated insulator layer. Gate electrodes were self-aligned to minimize overlap capacitance by inkjet printing that used the embossed grooves to define a surface-energy pattern.

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PubMed2003

Induced alignment of a solution-cast discotic hexabenzocoronene derivative for electronic devices investigated by surface X-ray diffraction.

A surface X-ray diffraction study is presented showing that highly ordered and uniaxially aligned hexa(3,7-dimethyl-octanyl)hexa-peri-hexabenzocoronene (HBC-C8,2) films can be fabricated by crystallization from solution onto friction-transferred poly(tetrafluoroethylene) (PTFE) layers. Three crystalline HBC-C8,2 majority phases result. In all three phases, the HBC-C8,2 molecules self-organize into columns which are uniaxially aligned along the direction defined by the PTFE macromolecules of the substrate. The three phases are quite similar, the major difference being their orientation with respect to the substrate. A quasi-2D epitaxial growth mechanism with a grapho-epitaxial component for one of the three phases explains the formation of the three rotational HBC-C8,2 variants. A method to obtain a thin film with only one phase is proposed. The results show that standard THETAV;-2THETAV; X-ray diffraction and transmission electron diffraction can be very misleading tools to estimate the crystalline quality in a thin film of complex structure.

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