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Graphene p–n–p junctions controlled by local gates made of naturally oxidized thin aluminium films
Nam, Youngwoo,Lindvall, Niclas,Sun, Jie,Park, Yung Woo,Yurgens, August Elsevier 2012 Carbon Vol.50 No.5
<P><B>Abstract</B></P><P>Graphene structures with both top- and bottom-electrostatic gates are studied. The top gate is made of thin aluminium (Al) film deposited directly onto graphene, with no prior dielectric layer in between. Natural oxidation of Al at the interface with graphene results in an insulating barrier proving useful in making top gates to graphene. For electrically disconnected top gate, graphene resistance as a function of the slowly-varying back-gate voltage shows hysteresis which reveals dielectric properties of the barrier. The estimated barrier thickness is only 2nm allowing for very sharp profiles of the electric field in graphene devices. By applying voltages to both back- and top gates, effective p–n–p junctions with sharp interfaces can be created.</P>
Determination of the Bending Rigidity of Graphene via Electrostatic Actuation of Buckled Membranes
Lindahl, Niklas,Midtvedt, Daniel,Svensson, Johannes,Nerushev, Oleg A.,Lindvall, Niclas,Isacsson, Andreas,Campbell, Eleanor E. B. American Chemical Society 2012 Nano letters Vol.12 No.7
<P>Classical continuum mechanics is used extensively to predict the properties of nanoscale materials such as graphene. The bending rigidity, κ, is an important parameter that is used, for example, to predict the performance of graphene nanoelectromechanical devices and also ripple formation. Despite its importance, there is a large spread in the theoretical predictions of κ for few-layer graphene. We have used the snap-through behavior of convex buckled graphene membranes under the application of electrostatic pressure to determine experimentally values of κ for double-layer graphene membranes. We demonstrate how to prepare convex-buckled suspended graphene ribbons and fully clamped suspended membranes and show how the determination of the curvature of the membranes and the critical snap-through voltage, using AFM, allows us to extract κ. The bending rigidity of bilayer graphene membranes under ambient conditions was determined to be 35.5<SUB>–15.0</SUB><SUP>+20.0</SUP> eV. Monolayers are shown to have significantly lower κ than bilayers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2012/nalefd.2012.12.issue-7/nl301080v/production/images/medium/nl-2012-01080v_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl301080v'>ACS Electronic Supporting Info</A></P>
The Aharonov-Bohm effect in graphene rings with metal mirrors
Nam, Y.,Yoo, J.S.,Park, Y.W.,Lindvall, N.,Bauch, T.,Yurgens, A. Pergamon Press ; Elsevier Science Ltd 2012 Carbon Vol.50 No.15
We measured the Aharonov-Bohm (AB) effect in graphene rings with superconducting-(Al) and normal-metal (Au) mirrors. The mirrors were deposited either on additional stubs connected to the rings in the transverse direction or on the ring bias lines. A significant enhancement of the visible phase coherence was observed in the latter case, in which we observed even the third harmonic of the AB oscillations. The superconductivity of the mirrors appears to be unimportant for the improved coherence in graphene. A large Fermi energy mismatch between graphene and the mirror material is sufficient for this effect. In addition, a transport gap was observed in our graphene structures at the gate voltage close to the Dirac point. The value of the gap can be reproduced by assuming the occurrence of Coulomb blockade effects in graphene.
Carbon nanotube field effect transistors with suspended graphene gates.
Svensson, Johannes,Lindahl, Niklas,Yun, Hoyeol,Seo, Miri,Midtvedt, Daniel,Tarakanov, Yury,Lindvall, Niclas,Nerushev, Oleg,Kinaret, Jari,Lee, Sangwook,Campbell, Eleanor E B American Chemical Society 2011 Nano letters Vol.11 No.9
<P>Novel field effect transistors with suspended graphene gates are demonstrated. By incorporating mechanical motion of the gate electrode, it is possible to improve the switching characteristics compared to a static gate, as shown by a combination of experimental measurements and numerical simulations. The mechanical motion of the graphene gate is confirmed by using atomic force microscopy to directly measure the electrostatic deflection. The device geometry investigated here can also provide a sensitive measurement technique for detecting high-frequency motion of suspended membranes as required, e.g., for mass sensing.</P>
Erta Kalanxhi,Karianne Risberg,Imon S. Barua,Svein Dueland,Stein Waagene,Solveig Norheim Andersen,Solveig J. Pettersen,Jessica M. Lindvall,Kathrine Røe Redalen,Kjersti Flatmark,Anne Hansen Ree 대한암학회 2017 Cancer Research and Treatment Vol.49 No.2
Purpose When integrating molecularly targeted compounds in radiotherapy, synergistic effects of the systemic agent and radiation may extend the limits of patient tolerance, increasing the demand for understanding the pathophysiological mechanisms of treatment toxicity. In this Pelvic Radiation and Vorinostat (PRAVO) study, we investigated mechanisms of adverse effects in response to the histone deacetylase (HDAC) inhibitor vorinostat (suberoylanilide hydroxamic acid, SAHA) when administered as a potential radiosensitiser. Materials and Methods This phase I study for advanced gastrointestinal carcinoma was conducted in sequential patient cohorts exposed to escalating doses of vorinostat combined with standard-fractionated palliative radiotherapy to pelvic target volumes. Gene expression microarray analysis of the study patient peripheral blood mononuclear cells (PBMC) was followed by functional validation in cultured cell lines and mice treated with SAHA. Results PBMC transcriptional responses to vorinostat, including induction of apoptosis, were confined to the patient cohort reporting dose-limiting intestinal toxicities. At relevant SAHA concentrations, apoptotic features (annexin V staining and caspase 3/7 activation, but not poly-(ADP-ribose)-polymerase cleavage) were observed in cultured intestinal epithelial cells. Moreover, SAHA-treated mice displayed significant weight loss. Conclusion The PRAVO study design implemented a strategy to explore treatment toxicity caused by an HDAC inhibitor when combined with radiotherapy and enabled the identification of apoptosis as a potential mechanism responsible for the dose-limiting effects of vorinostat. To the best of our knowledge, this is the first report deciphering mechanisms of normal tissue adverse effects in response to an HDAC inhibitor within a combined-modality treatment regimen.