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Search Results: 1 - 10 of 458 matches for " Viera Skakalova "
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Growth and properties of few-layer graphene prepared by chemical vapor deposition
Hye Jin Park,Jannik Meyer,Siegmar Roth,Viera Skakalova
Physics , 2009, DOI: 10.1016/j.carbon.2009.11.030
Abstract: The structure, and electrical, mechanical and optical properties of few-layer graphene (FLG) synthesized by chemical vapor deposition (CVD) on a Ni coated substrate were studied. Atomic resolution transmission electron microscope (TEM) images show highly crystalline single layer parts of the sample changing to multilayer domains where crystal boundaries are connected by chemical bonds. This suggests two different growth mechanisms. CVD and carbon segregation participate in the growth process and are responsible for the different structural formations found. Measurements of the electrical and mechanical properties on the centimeter scale provide evidence of a large scale structural continuity: 1) in the temperature dependence of the electrical conductivity, a non-zero value near 0 K indicates the metallic character of electronic transport; 2) the Young's modulus of a pristine polycarbonate film (1.37 GPa) improves significantly when covered with FLG (1.85 GPa). The latter indicates an extraordinary Young modulus value of the FLG-coating of TPa orders of magnitude. Raman and optical spectroscopy support the previous conclusions. The sample can be used as a flexible and transparent electrode and is suitable for special membranes to detect and study individual molecules in high resolution TEM.
Transconductance fluctuations as a probe for interaction induced quantum Hall states in graphene
Dong Su Lee,Viera Skakalova,R. Thomas Weitz,Klaus von Klitzing,Jurgen H. Smet
Physics , 2012, DOI: 10.1103/PhysRevLett.109.056602
Abstract: Transport measurements normally provide a macroscopic, averaged view of the sample, so that disorder prevents the observation of fragile interaction induced states. Here, we demonstrate that transconductance fluctuations in a graphene field effect transistor reflect charge localization phenomena on the nanometer scale due to the formation of a dot network which forms near incompressible quantum states. These fluctuations give access to fragile broken-symmetry and fractional quantum Hall states even though these states remain hidden in conventional magnetotransport quantities.
Correlation between resistance fluctuations and temperature dependence of conductivity in graphene
Viera Skakalova,Alan B. Kaiser,Jai Seung Yoo,Dirk Obergfell,Siegmar Roth
Physics , 2009, DOI: 10.1103/PhysRevB.80.153404
Abstract: The weak temperature dependence of the resistance R(T) of monolayer graphene1-3 indicates an extraordinarily high intrinsic mobility of the charge carriers. Important complications are the presence of mobile scattering centres that strongly modify charge transport, and the presence of strong mesoscopic conductance fluctuations that, in graphene, persist to relatively high temperatures4,5. In this Letter, we investigate the surprisingly varied changes in resistance that we find in graphene flakes as temperature is lowered below 70 K. We propose that these changes in R(T) arise from the temperature dependence of the scattered electron wave interference that causes the resistance fluctuations. Using the field effect transistor configuration, we verify this explanation in detail from measurements of R(T) by tuning to different gate voltages corresponding to particular features of the resistance fluctuations. We propose simple expressions that model R(T) at both low and high charge carrier densities.
Raman Scattering at Pure Graphene Zigzag Edges
Benjamin Krauss,Péter Nemes-Incze,Viera Skakalova,László P. Biro,Klaus von Klitzing,Jurgen H. Smet
Physics , 2010, DOI: 10.1021/nl102526s
Abstract: Theory has predicted rich and very distinct physics for graphene devices with boundaries that follow either the armchair or zigzag crystallographic directions. A prerequisite to disclose this physics in experiment is to be able to produce devices with boundaries of pure chirality. Exfoliated flakes frequently exhibit corners with an odd multiple of 30{\deg}, which raised expectations that their boundaries follow pure zigzag and armchair directions. The predicted Raman behavior at such crystallographic edges however failed to confirm pure edge chirality. Here, we perform confocal Raman spectroscopy on hexagonal holes obtained after the anisotropic etching of prepatterned pits using carbothermal decomposition of SiO2. The boundaries of the hexagonal holes are aligned along the zigzag crystallographic direction and leave hardly any signature in the Raman map indicating unprecedented purity of the edge chirality. This work offers the first opportunity to experimentally confirm the validity of the Raman theory for graphene edges.
Electronic Transport in Composites of Graphite Oxide with Carbon Nanotubes
Viera Skakalova,Viliam Vretenar,Lubomir Kopera,Peter Kotrusz,Clemens Mangler,Marcel Mesko,Jannik C. Meyer,Martin Hulman
Physics , 2013,
Abstract: We show that the presence of electrically insulating graphite oxide (GO) within a single wall carbon nanotube network strongly enhances electrical conductivity, whereas reduced graphite oxide, even though electrically conductive, suppresses electrical conductivity within a composite network with single wall carbon nanotubes. Measurements of Young modulus and of Raman spectra strongly support our interpretation of the indirect role of the oxide groups, present in graphite oxide within the single wall carbon nanotubes/graphite oxide composite, through electronic doping of metallic single wall carbon nanotubes.
Charged defects in graphene and the ionicity of hexagonal boron nitride in direct images
Jannik C. Meyer,Simon Kurasch,Hye Jin Park,Viera Skakalova,Daniela Künzel,Axel Gro?,Andrey Chuvilin,Gerardo Algara-Siller,Siegmar Roth,Takayuki Iwasaki,Ulrich Starke,Jürgen Smet,Ute Kaiser
Physics , 2010,
Abstract: We report on the detection and charge distribution analysis for nitrogen substitutional dopants in single layer graphene membranes by aberration-corrected high-resolution transmission electron microscopy (HRTEM). Further, we show that the ionicity of single-layer hexagonal boron nitride can be confirmed from direct images. For the first time, we demonstrate by a combination of HRTEM experiments and first-principles electronic structure calculations that adjustments to the atomic potentials due to chemical bonding can be discerned in HRTEM images. Our experiments open a way to discern electronic configurations in point defects or other non-periodic arrangements or nanoscale objects that can not be analyzed in an electron or x-ray diffraction experiment.
NINTH-GRADE STUDENTS' RESULTS OF EXERCISES TO DETERMINE MATHEMATICAL LITERACY IN THE 2007/2008 SCHOOL YEAR TESTING TESTOVANIE 9' / Vysledky deviatakov v úlohách na zis ovanie matematickej gramotnosti v testovaní 9 v kolskom roku 2007/2008
Ringlerová Viera
Technológia vzdelávania , 2008,
Abstract: The mathematics' test in the full-area testing 'Testovanie 9' in the school year 2007/2008 consisted of two parts. This paper deals with students' results in the II part of the test.V kolskom roku 2007/2008 v celoplo nom Testovaní 9 sa test z matematiky skladal z dvoch astí. V príspevku uvádzame vysledky iakov z II. asti testu.
Medzinárodné projekty a u enie sa prostredníctvom novych skúseností:spolupráca Katedry pedagogiky PF UKF v Nitre s vysoko kolskymi in titúciami v Belgicku
Kurincová Viera
Technológia vzdelávania , 2011,
Abstract: Autorka sa v príspevku zaoberá medzinárodnou spoluprácou a jej vyznamnom vo vzdelávaní budúcich u ite ov a u ite ov vysokych k l. Pribli uje 20. ro né skúsenosti so spolupráce KPg PF UKF v Nitre s KH Leuven v Belgicku.
Review: Angela Kaupp (2005). Junge Frauen erz hlen ihre Glaubensgeschichte. Eine qualitativ-empirische Studie zur Rekonstruktion der narrativen religi sen Identit t katholischer junger Frauen Review: Angela Kaupp (2005). Junge Frauen erz hlen ihre Glaubensgeschichte. Eine qualitativ-empirische Studie zur Rekonstruktion der narrativen religi sen Identit t katholischer junger Frauen [Young Women Tell Their Story of Faith] Rese a: Angela Kaupp (2005). Junge Frauen erz hlen ihre Glaubensgeschichte. Eine qualita
Viera Pirker
Forum : Qualitative Social Research , 2007,
Abstract: Angela KAUPP geht in ihrer religionsp dagogischen Dissertation der Frage nach, wie sich Religiosit t in der Lebensgeschichte katholisch sozialisierter junger Frauen entfaltet. Die Kategorien Geschlecht und Religiosit t wurden in der Jugendforschung bislang wenig berücksichtigt. Die lesenswerte Studie schlie t eine Lücke zwischen der p dagogischen, sozialwissenschaftlichen und religionsp dagogischen Forschung. Geschlecht und Religiosit t werden von den befragten Frauen weitgehend als unabh ngig voneinander und von ihrer Lebensgeschichte eingestuft. Von hoher Bedeutung ist die Er ffnung von religi sen Kommunikations- und Beziehungsangeboten sowie authentischer atmosph rischer R ume, z.B. in der Liturgie der Gemeinde. KAUPP zeigt, dass Biographieforschung sich mit einigen Modifikationen als geeignete Methode erweist, die Identit tsentwicklung junger Erwachsener auch im Kontext von Religiosit t und Geschlecht zu erforschen. URN: urn:nbn:de:0114-fqs0701183 In her dissertation on religious pedagogy, Angela KAUPP examines the part played by religiousness in the life stories of young women brought up as Catholics in Germany. The categories of gender and religiousness are still neglected fields in youth studies and KAUPP's readable study closes a gap in research on religious and social-scientific research on pedagogy. The interviewees consider gender and religiousness to be independent and to have few implications for their life stories. They attribute high importance to religious communication, relations and spaces as part of formal and informal religious settings such as the liturgy and prayer groups. KAUPP's work indicates that biographical research is a promising method for the exploration of the development of young adults' identities in the context of religiousness and gender. URN: urn:nbn:de:0114-fqs0701183 En su estudio sobre la pedagogía religiosa, Angela KAUPP examina el papel de lo religioso en Alemania mediante historias de vida de chicas con educación católica. Las categorías de género y religiosidad son campos a menudo olvidados en estudios con jóvenes y el ameno trabajo de KAUPP supera esa brecha en la investigación científico-social de la religiosidad y la pedagogía. Las entrevistadas consideran el género y la religiosidad como algo independiente y que tiene pocas implicaciones en sus vidas. Atribuyen una gran importancia a la comunicación, las relaciones y los espacios religiosos como una parte más de las convenciones religiosas, como la liturgia y las agrupaciones. El trabajo de KAUPP muestra que la investigación biográfica es un método promete
Prejavy personalizácie líderstva: perspektívy slovenskych straníckych lídrov vo vz ahu k medializácii
Viera ?úborová
St?edoevropské Politické Studie , 2011,
Abstract: Expressions of the Personalization of Leadership: Perspectives of Slovak Party Leaders in Relation to their media Coverage. This study examines the impact and position of party leaders in relation to the personalization of politics in the Slovak Republic. It identifies personalization in the media, expressed by an increase in the focus of media coverage on individual politicians. The main objective is to show the nature and presentation of party leaders in relation to the concept of personalization, as well as in relation to the type of presentation (negative, positive, or neutral). The study is based on the common finding that if the political party has a dominant and stable position within the system and the party leader has a strong and charismatic personal characteristic (valence), her or she is presented through positive or neutral messages rather than negative, and vice versa.
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