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Register a new userFunctional surfaces through the creation of adhesion and charged patterns on azopolymer surface relief gratings
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We show that an azopolymer can be used to create a supramolecular architecture in a parallel process with patterned surface properties. By illuminating with an interference pattern, we created adhesion and charge patterns that reflect the molecular ordering. We studied the recording process in two limit situations. When birefringence dominates over mass transport, an adhesion pattern was recorded even in absence of a surface relief grating (SRG). When mass transport dominates, we measured a higher frequency adhesion and relief patterns on top of the SRG. We measured an increased negative charge in the regions where molecules are expected to be parallel aligned in trans conformational state.
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We investigate theoretically the adhesion and electronic properties of graphene on a muscovite mica surface using the density functional theory (DFT) with van der Waals (vdW) interactions taken into account (the vdW-DF approach). We found that irregularities in the local structure of cleaved mica surface provide different mechanisms for the mica-graphene binding. By assuming electroneutrality for both surfaces, the binding is mainly of vdW nature, barely exceeding thermal energy per carbon atom at room temperature. In contrast, if potassium atoms are non uniformly distributed on mica, the different regions of the surface give rise to $n$- or $p$-type doping of graphene. In turn, an additional interaction arises between the surfaces, significantly increasing the adhesion. For each case the electronic states of graphene remain unaltered by the adhesion. It is expected, however, that the Fermi level of graphene supported on realistic mica could be shifted relative to the Dirac point due to asymmetry in the charge doping. Obtained variations of the distance between graphene and mica for different regions of the surface are found to be consistent with recent atomic force microscopy experiments. A relative flatness of mica and the absence of interlayer covalent bonding in the mica-graphene system make this pair a promising candidate for practical use.
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