TY - JOUR AU - Wecker, Tobias AU - Callsen, Gordon AU - Hoffmann, Axel AU - Reuter, Dirk AU - As, Donat Josef ID - 7055 IS - 5S JF - Japanese Journal of Applied Physics SN - 0021-4922 TI - Photoluminescence excitation spectroscopy of excited states of an asymmetric cubic GaN/Al0.25Ga0.75N double quantum well grown by molecular beam epitaxy VL - 55 ER - TY - JOUR AB - We investigate the band dispersion and related electronic properties of picene single crystals within the GW approximation for the electronic self-energy. The width of the upper highest occupied molecular orbital (HOMOu) band along the Γ–Y direction, corresponding to the b crystal axis in real space along which the molecules are stacked, is determined to be 0.60 eV and thus 0.11 eV larger than the value obtained from density-functional theory. As in our recent study of rubrene using the same methodology [S. Yanagisawa, Y. Morikawa, and A. Schindlmayr, Phys. Rev. B 88, 115438 (2013)], this increase in the bandwidth is due to the strong variation of the GW self-energy correction across the Brillouin zone, which in turn reflects the increasing hybridization of the HOMOu states of neighboring picene molecules from Γ to Y. In contrast, the width of the lower HOMO (HOMOl) band along Γ–Y remains almost unchanged, consistent with the fact that the HOMOl(Γ) and HOMOl(Y) states exhibit the same degree of hybridization, so that the nodal structure of the wave functions and the matrix elements of the self-energy correction are very similar. AU - Yanagisawa, Susumu AU - Morikawa, Yoshitada AU - Schindlmayr, Arno ID - 18473 IS - 5S1 JF - Japanese Journal of Applied Physics SN - 0021-4922 TI - Theoretical investigation of the band structure of picene single crystals within the GW approximation VL - 53 ER - TY - JOUR AB - The electrooptic characteristics of the field-induced reorientation of a nematic liquid crystal are studied using graphene layers as transparent conductive electrodes. The covering of a large area with highly conductive graphene was achieved by the thermal reduction of a graphene oxide film. The conductivity of the graphene electrode provides electrooptic properties that are comparable to those of liquid crystal cells with two conventional indium tin oxide electrodes. This result confirms earlier studies and suggestions concerning graphene-based liquid crystal devices. It demonstrates that the fabrication of graphene layers via the deposition and subsequent reduction of graphene oxide is suitable for liquid crystal applications. AU - Nordendorf, Gaby AU - Kasdorf, Olga AU - Kitzerow, Heinz-Siegfried AU - Liang, Yanyu AU - Feng, Xinliang AU - Müllen, Klaus ID - 39739 IS - 10R JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - Liquid Crystal Addressing by Graphene Electrodes Made from Graphene Oxide VL - 49 ER - TY - JOUR AU - Kasdorf, Olga AU - Kitzerow, Heinz-Siegfried AU - Lenoble-Zwahlen, Julie AU - Deschenaux, Robert ID - 39745 IS - 1 JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - Physics and Astronomy (miscellaneous) KW - General Engineering SN - 0021-4922 TI - Influence of a Mesogenic Dendrimer on the Morphology of Polymer–Fullerene Composites for Photovoltaics VL - 49 ER - TY - JOUR AB - The present study shows that a cholesteric gel consisting of a low molar mass liquid crystal and a highly crosslinked anisotropic network can be switched between a transparent and a colored scattering state. The latter state can be induced in an initially non-aligned cholesteric liquid crystal by an electric field, as described recently by Chilaya and coworkers. A short pulse of an electric field can be used to select between the two states which are stable at zero field. The angular dependence of the wavelength of the diffracted light is studied in detail and explained by the known properties of the spatially periodic cholesteric structure. AU - Kitzerow, Heinz-Siegfried ID - 40298 IS - 3B JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - Bistable Diffractive Electro-Optical Effect in Cholesteric Gels* VL - 36 ER - TY - JOUR AB - The electrooptic properties due to the transient light scattering mode (TSM) are studied for non-aligned ferroelectric and antiferro-electric liquid crystals with short pitch. The transient light scattering appears in thick samples without polarizers if the sign of an applied dc field is reversed. As a consequence, an ac field of suitable frequency can be used to switch the sample from a transparent to a scattering state. Due to the short pitch, a colored scattering can be observed under oblique angles. The latter effect provides high contrast ratios. AU - Kitzerow, Heinz-Siegfried ID - 40300 IS - 1R JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - Transient Light Scattering of a Ferroelectric and an Antiferroelectric Liquid Crystal with Short Pitch VL - 36 ER - TY - JOUR AB - Most electrooptic effects in liquid crystals require a uniform orientation of the director at the glass substrates. A new method to produce suitable alignment layers is based on the creation of anisotropic polymer films by photopolymerization with linearly polarized light. In the present paper we report on measurements of the anchoring strength of these photo-induced anisotropic films. Using a wedge-cell technique, we find an azimuthal anchoring energy of W ϕ≈2.3·10-6 J/m2. AU - Vorflusev, Valery P. AU - Kitzerow, Heinz-Siegfried AU - Chigrinov, Vladimir G. ID - 40315 IS - 9A JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - Azimuthal Anchoring Energy in Photoinduced Anisotropic Films VL - 34 ER - TY - JOUR AB - A novel technique to produce planar and homeotropic alignment of smectic liquid crystals is presented. The technique is based on producing an anisotropic polymer network in the bulk by photo-polymerizing a mixture of photoresist material and liquid crystal by linearly polarized UV-light. Both uniform planar alignment and homeotropic alignment can be obtained depending on the curing conditions. In the case of planar alignment, the orientation of liquid crystal molecules is governed by the direction of the polarization vector of the UV-light, thus making it possible to produce a defined azimuthal orientation of the liquid crystal director. This technique obviates the need to give any previous treatment to the bounding substrates. AU - Jain, Sukhmal C. AU - Kitzerow, Heinz-Siegfried ID - 40317 IS - 5A JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - A New Method to Align Smectic Liquid Crystals by Photo-Polymerization VL - 33 ER - TY - JOUR AB - We investigated the switching behavior of the well-known antiferroelectric liquid crystal (R)-4-(1-methylheptyloxycarbonyl)phenyl-4'-octyloxybiphenyl-4-carboxylate (MHPOBC), embedded in a polymer matrix. The alignment of the liquid crystal in the UV-cured adhesive was controlled by mechanical shear during the polymerization-induced phase separation. Multistable switching with time constants down to 150 µs indicates that antiferroelectric PDLC devices are promissing for electrooptic application as flexible displays. AU - Molsen, Henning AU - Kitzerow, Heinz-Siegfried AU - Heppke, Gerd ID - 40328 IS - 8A JF - Japanese Journal of Applied Physics KW - General Physics and Astronomy KW - General Engineering SN - 0021-4922 TI - Antiferroelectric Switching in Polymer-Dispersed Liquid Crystals VL - 31 ER -