@article{MikayelyanGroddKsianzouetal.2019, author = {Mikayelyan, Eduard and Grodd, Linda and Ksianzou, Viachaslau and Wesner, Daniel and Rodygin, Alexander I. and Sch{\"o}nherr, Holger and Luponosov, Yuriy N. and Ponomarenko, Sergei A. and Ivanov, Dimitri A. and Pietsch, Ullrich and Grigorian, Souren}, title = {Phase Transitions and Formation of a Monolayer-Type Structure in Thin Oligothiophene Films: Exploration with a Combined In Situ X-ray Diffraction and Electrical Measurements}, series = {Nanoscale Research Letters}, volume = {14}, journal = {Nanoscale Research Letters}, issn = {1556-276X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12314}, year = {2019}, abstract = {A combination of in situ electrical and grazing-incidence X-ray diffraction (GIXD) is a powerful tool for studies of correlations between the microstructure and charge transport in thin organic films. The information provided by such experimental approach can help optimizing the performance of the films as active layers of organic electronic devices. In this work, such combination of techniques was used to investigate the phase transitions in vacuum-deposited thin films of a common organic semiconductor dihexyl-quarterthiophene (DH4T). A transition from the initial highly crystalline phase to a mesophase was detected upon heating, while only a partial backward transition was observed upon cooling to room temperature. In situ electrical conductivity measurements revealed the impact of both transitions on charge transport. This is partly accounted for by the fact that the initial crystalline phase is characterized by inclination of molecules in the plane perpendicular to the π-π stacking direction, whereas the mesophase is built of molecules tilted in the direction of π-π stacking. Importantly, in addition to the two phases of DH4T characteristic of the bulk, a third interfacial substrate-stabilized monolayer-type phase was observed. The existence of such interfacial structure can have important implications for the charge mobility, being especially favorable for lateral two-dimensional charge transport in the organic field-effect transistors geometry.}, language = {en} } @article{GrytsenkoKsianzouKolomzarovetal.2021, author = {Grytsenko, Kostyantyn and Ksianzou, Viachaslau and Kolomzarov, Yurii and Lytvyn, Peter and Dietzel, Birgit and Schrader, Sigurd}, title = {Fluoropolymer Film Formation by Electron Activated Vacuum Deposition}, series = {Surfaces}, volume = {4}, journal = {Surfaces}, number = {1}, publisher = {MDPI}, issn = {2571-9637}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13786}, pages = {66 -- 80}, year = {2021}, abstract = {Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a factor five in the presence of the electron cloud. Mass spectrometry revealed changes in the mass spectra of fragments generated by thermal decomposition only and formed under electron activation. The observed changes were different for each fluoropolymer. Infrared spectroscopy (IRS) showed that the structure of the films was close to the structure of the bulk polymers. Atomic force microscopy (AFM) has revealed different morphologies of PTFE, PHFP and PCTFE films, suggesting a Volmer-Weber growth mechanism for PTFE and PHFP but a Frank-van der Merwe one for PCTFE. All films were smooth at nanoscale and transparent from ultraviolet to near-infrared region. Additional radio frequency (RF) plasma ignited in the emitted fragments at a low pressure increased mechanical characteristics of the films without losing their optical transparency and smoothness.}, language = {en} } @inproceedings{PadillaMichelPulwerSaffarietal.2016, author = {Padilla-Michel, Yazmin and Pulwer, Silvio and Saffari, Pouneh and Ksianzou, Viachaslau and Schrader, Sigurd}, title = {On the origin and removal of interference patterns in coated multimode fibres}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15295}, pages = {1517 -- 1527}, year = {2016}, abstract = {In this study, we present the experimental investigations on interference patterns, such as those already reported in VIMOS-IFU, and up to now no appropriate explanation has been presented. These interference patterns are produced in multimode fibres coated with acrylate or polyimide, which is the preferred coating material for the fibres used in IFUs. Our experiments show that, under specific conditions, cladding modes interact with the coating and produce interference. Our results show that the conditions at which the fibre is held during data acquisition has an impact in the output spectrum. Altering the positioning conditions of the fibre leads to the changes into the interference pattern, therefore, fibres should be carefully manipulated in order to minimise this potential problem and improve the performance of these instruments. Finally we present a simple way of predicting and modelling this interference produced from the visible to the near infrared spectra. This model can be included in the data reduction pipeline in order to remove the interference patterns. These results should be of interest for the optimisation of the data reduction pipelines of instruments using optical fibres. Considering these results will benefit innovations and developments of high performance fibre systems.}, language = {en} } @article{KsianzouVelagapudiGrimmetal.2006, author = {Ksianzou, Viachaslau and Velagapudi, R. K. and Grimm, Bernd and Schrader, Sigurd}, title = {Polarization-dependent optical characterization of poly(phenylquinoxaline) thin films}, series = {Journal of Applied Physics}, volume = {100}, journal = {Journal of Applied Physics}, number = {6}, issn = {1089-7550}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9761}, year = {2006}, abstract = {Linear optical properties of two types of poly(phenylquinoxaline) (PPQ) are studied by multiwavelength prism coupling technique and optical absorption spectroscopy. Surface roughness measurements are done using atomic force microscopy. PPQs form smooth films of high optical quality having refractive indices above 1.7 in the visible and near infrared spectral ranges. Enhanced birefringence of Δn∼0.04Δn∼0.04 has been observed in both PPQ films prepared by spin coating. Sellmeier coefficients are derived for the wavelength range starting from 0.532to1.064μm0.532to1.064μm for both TE and TM polarizations. Quantum chemical calculations both on the semiempirical and on the ab initio level are carried out in order to calculate the first-order molecular polarizability tensors of the polymer repeat units. From the obtained tensor elements, theoretical values for both the average refractive indices and the maximum expectable birefringence are calculated. Based on these values a more detailed interpretation of the experimental findings is carried out. The dispersion of refractive index is quantified by the value of Abbe's constant (νd)(νd). In our case the value νd≈11νd≈11 indicates high dispersion in the visible spectral range. The imaginary part kk of the complex refractive index n∗=n-ikn*=n-ik reaches values of k⩽10-3k⩽10-3 in the wavelength range from 0.5to1μm0.5to1μm.}, language = {en} } @inproceedings{GrytsenkoDoroshenkoKolomzarovetal.2008, author = {Grytsenko, Kostyantyn and Doroshenko, T. and Kolomzarov, Yurii and Prokopets, Vadym M. and Fedoriak, O. and Zelinski, R. and Lytvyn, Oksana and Prescher, Dietrich and Grimm, Bernd and Ksianzou, Viachaslau and Schrader, Sigurd and Tolmachev, O. I. and Slominskii, Yu L. and Kurdiukov, V. and Smirnova, G.}, title = {Research on the growth of dye film in vacuum in situ}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15206}, pages = {318 -- 323}, year = {2008}, abstract = {Organic film deposition in vacuum is fast developing scientific and industrial domain. We developed installation for deposition of organic films equipped with optical spectrometer for measurements in situ. We are developing new dyes aimed for application in waveguide sensor, nonlinear optics and studying film organisation during deposition. Fluorinated azo-dyes and azomethine dyes were synthesized at University of Applied Sciences Wildau and at the Institute of Organic Chemistry, Kyiv. Compounds were evaporated at a pressure of 10-3 Pa using resistive heated crucible. Glass and glass covered with polytetrafluoroethylene (PTFE) film are used as substrates. The films were studied with Polytec and StellarNet spectrometers and an atomic force microscope. Optical spectra of the dye films revealed, that some compounds were decomposed during evaporation. Several kinds of dyes were evaporated and deposited without decomposition. Some deposited films formed H-aggregates and other types of aggregates. AFM images of dye films showed that their morphology depends on the chemical structure of the compounds and on the nature of the substrate on which the film was grown.}, language = {en} } @article{KsianzouVillringerGrytsenkoetal.2025, author = {Ksianzou, Viachaslau and Villringer, Claus and Grytsenko, Kostyantyn and Pekur, Demyd and Lytvyn, Peter and Sopinskyy, Mykola and Lebedyeva, Iryna and Niemczyk, Agata and Baranowska, Jolanta}, title = {Structural and Optical Anomalies in Thin Films Grown in a Magnetic Field by Electron-Assisted Vacuum Deposition of PTFE}, series = {Macromolecular Materials and Engineering}, volume = {310}, journal = {Macromolecular Materials and Engineering}, number = {3}, publisher = {Wiley}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19712}, year = {2025}, abstract = {Polytetrafluoroethylene (PTFE) films are deposited in parallel and perpendicular magnetic fields (MF) by electron-enhanced vacuum deposition (EVD) and EVD + low-temperature plasma (LTP) methods. The structure, morphology, and nanomechanical properties of the films are studied by infrared spectroscopy (IRS), atomic force microscopy (AFM), and spectroscopic ellipsometry. The structure of the thicker films is closer to that of bulk PTFE than that of thin films. The films' crystallinity and surface roughness are higher than those deposited without MF. The birefringence of the refractive index (n) of the films deposited in the MF is inverse to the anisotropy of the n of the films deposited without MF. The hardness of the films is close to that of bulk PTFE.}, language = {en} } @inproceedings{MeisterAlSaadiFrankeetal.2010, author = {Meister, Stefan and Al-Saadi, Aws and Franke, B{\"u}lent A. and Mahdi, Shaimaa and Kuhlow, Berndt and Voigt, Karsten and Tillack, Bernd and Richter, Harald H. and Zimmermann, Lars and Ksianzou, Viachaslau and Schrader, Sigurd and Eichler, Hans J.}, title = {Photonic crystal microcavities in SOI waveguides produced in a CMOS environment}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15223}, pages = {330 -- 339}, year = {2010}, abstract = {We have investigated microcavities in Silicon-on-Insolator (SOI) waveguides. The rectangular waveguides with 500 nm width are fabricated in the 220 nm silicon device layer. The microcavities are formed by one-dimensional photonic crystals in Fabry-Perot structure directly written in the waveguides. The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography, where the waveguides as well as the photonic crystals are created in the same step using a single mask. In order to achieve a desired spectral shape of the filter function capable for several applications, a number of different cavities were investigated, e.g. single cavities of first and higher order as well as multi-cavity filters. The experimental results are compared with simulations of photonic crystal microcavities in strip waveguides. The spectral transmission function of such filters dependent on the design parameters are calculated by an analysis based on Finite-Difference-Time-Domain (FDTD) method.}, language = {en} } @inproceedings{WangMeisterMahdietal.2011, author = {Wang, Sha and Meister, Stefan and Mahdi, Shaimaa and Franke, B{\"u}lent A. and Al-Saadi, Aws and Zimmermann, Lars and Richter, Harald H. and Stolarek, David and Lisinetskii, Viktor and Ksianzou, Viachaslau and Schrader, Sigurd and Eichler, Hans J.}, title = {Spontaneous and stimulated Raman scattering in planar silicon waveguides}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15248}, pages = {281 -- 289}, year = {2011}, abstract = {Raman scattering in planar silicon on insulator (SOI) waveguides with 2 μm width, 220 nm height and 2 cm length is investigated. A cw Nd:YAP laser at 1340.6 nm with 7 GHz FWHM spectral width is used as the pump source. A lensed fiber of 2.5 μm focus diameter is used to couple the pump laser into the waveguide. The coupling efficiency is estimated to be around 10\%. Spontaneous Raman scattering is observed with as low as 2.5 mW pump power inside the waveguide. The spontaneous Raman spectrum is measured by an optical spectrum analyzer. The first order Raman peak is measured at around 1441.4 nm corresponding to a Raman shift of 15.6 THz, while the FWHM of Raman spectrum is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22 mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the relationship between spontaneous Raman output power and pump power. A temperature dependence of Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power, around 0.6 dB gain has been determined with both pump and probe being TE polarized.}, language = {en} } @article{SteglichMaiVillringeretal.2021, author = {Steglich, Patrick and Mai, Christian and Villringer, Claus and Dietzel, Birgit and Bondarenko, Siegfried and Ksianzou, Viachaslau and Villasmunta, Francesco and Zesch, Christoph and Pulwer, Silvio and Burger, Martin and Bauer, Joachim and Heinrich, Friedhelm and Schrader, Sigurd and Vitale, Francesco and De Matteis, Fabio and Prosposito, Paolo and Casalboni, Mauro and Mai, Andreas}, title = {Silicon-organic hybrid photonics: an overview of recent advances, electro-optical effects and CMOS integration concepts}, series = {Journal of Physics: Photonics}, volume = {3}, journal = {Journal of Physics: Photonics}, number = {2}, issn = {2515-7647}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13882}, year = {2021}, abstract = {In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon-organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon-organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given.}, language = {en} } @misc{SteglichVillringerPulweretal.2017, author = {Steglich, Patrick and Villringer, Claus and Pulwer, Silvio and Dietzel, Birgit and Ksianzou, Viachaslau and Schrader, Sigurd}, title = {Chip-integrierte photonische Bauelemente}, series = {Wissenschaftliche Beitr{\"a}ge 2017}, volume = {21}, journal = {Wissenschaftliche Beitr{\"a}ge 2017}, issn = {0949-8214}, doi = {10.15771/0949-8214_2017_7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9426}, pages = {55 -- 59}, year = {2017}, abstract = {In unserer hochtechnologisierten Gesellschaft spielt die optische Daten{\"u}bertragung aufgrund der stetig wachsenden Informationsvielfalt eine immer bedeutendere Rolle. In den Anf{\"a}ngen der Nachrichtentechnik waren Datenraten von wenigen bit/s realisierbar. Heute werden mittels optischer Technologien {\"U}bertragungsraten von mehreren Gbit/s umgesetzt. M{\"o}glich wird dies durch neue Entwicklungen in der Chip-integrierten Photonik. Beispiele daf{\"u}r sind Chip-integrierte elektrooptische Modulatoren und Schalter. In diesem Artikel werden neue Entwicklungen in der Chip-integrierten Photonik diskutiert und die experimentelle Charakterisierung der Bauelemente in Form eines Ringresonators beschrieben. F{\"u}r die Experimente wird exemplarisch ein photonisches Bauelement genutzt, das aus einem hybriden Silizium-Polymer-Materialsystem besteht. Die Ergebnisse zeigen, dass diese Materialkombination vielversprechend f{\"u}r zuk{\"u}nftige Chip-integrierte photonische Bauelemente mit extrem geringem Energiebedarf ist.}, language = {de} } @misc{SteglichKsianzouVillringeretal.2018, author = {Steglich, Patrick and Ksianzou, Viachaslau and Villringer, Claus and Pulwer, Silvio and Schrader, Sigurd}, title = {Theorie der Modenlinienspektroskopie zur optischen Charakterisierung von Polymerschichten}, series = {Wissenschaftliche Beitr{\"a}ge 2018}, volume = {22}, journal = {Wissenschaftliche Beitr{\"a}ge 2018}, issn = {0949-8214}, doi = {10.15771/0949-8214_2018_4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10248}, pages = {31 -- 38}, year = {2018}, abstract = {Die Modenlinienspektroskopie kann zur hochpr{\"a}zisen Charakterisierung von Polymerschichten bez{\"u}glich des Brechungsindex verwendet werden. Das vorliegende Manuskript behandelt die Theorie der Modenlinienspektroskopie und beginnt dabei mit den theoretischen Grundlagen eines planaren Wellenleiters, die zum Verst{\"a}ndnis der Modenlinienspektroskopie notwendig sind. Die hier pr{\"a}sentierten expliziten Herleitungen k{\"o}nnen genutzt werden, um die Modenlinienspektroskopie so zu modifizieren, dass auch die Messung des Pockelseffektes m{\"o}glich ist. Eine Anwendungsm{\"o}glichkeit soll in der zuk{\"u}nftigen Bestimmung des Pockelskoeffizienten bestehen, der f{\"u}r die Weiterentwicklung von polymerbasierten elektrooptischen Modulatoren ben{\"o}tigt wird. Zudem werden der Aufbau und die experimentelle Herangehensweisen beschrieben und die Brechungsindexbestimmung wird exemplarisch am Beispiel einer Wirt-Gast-Polymerschicht demonstriert.}, language = {de} }