ÚFI-odbor fyziky pevných látek a povrchů

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    Electron beam directed etching of hexagonal boron nitride
    (Royal Society of Chemistry, 2016-09-28) Elbadawi, Christopher; Tran, Trong Toan; Kolíbal, Miroslav; Šikola, Tomáš; Scott, John; Cai, Qiran; Li, Lu Hua; Taniguchi, Takashi; Watanabe, Kenji; Toth, Milos; Aharonovich, Igor; Lobo, Charlene
    Hexagonal boron nitride (hBN) is a wide bandgap van der Waals material with unique optical properties that make it attractive for two dimensional (2D) photonic and optoelectronic devices. However, broad deployment and exploitation of hBN is limited by alack of suitable material and device processing and nano prototyping techniques. Here we present a high resolution, single step electron beam technique for chemical dry etching of hBN. Etching is achieved using H2O as a precursor gas, at both room temperature and elevated hBN temperatures. The technique enables damage-free, nano scale, iterative patterning of supported and suspended 2D hBN, thus opening the door to facile fabrication of hBN-based 2D heterostructures and devices.
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    Magneto-optical investigations of molecular nanomagnet monolayers
    (Royal Society of Chemistry, 2016-04-11) Rozbořil, Jakub; Rechkemmer, Y.; Bloos, Dominik; Münz, Filip; Wang, C. Nan; Neugebauer, Petr; Čechal, Jan; Novák, Jiří; van Slageren, Joris
    We report field-dependent magnetization measurements on monolayers of [Dy(Pc)2] on quartz, prepared by the Langmuir–Blodgett technique. The films are thoroughly characterized by means of X-ray reflectivity and atomic force microscopy. The magnetisation of the sample is measured through the magnetic circular dichroism of a ligand-based electronic transition.
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    X-ray induced electrostatic graphene doping via defect charging in gate dielectric
    (NPG, 2017-04-03) Procházka, Pavel; Mareček, David; Lišková, Zuzana; Čechal, Jan; Šikola, Tomáš
    Graphene field effect transistors are becoming an integral part of advanced devices. Hence, the advanced strategies for both characterization and tuning of graphene properties are required. Here we show that the X-ray irradiation at the zero applied gate voltage causes very strong negative doping of graphene, which is explained by X-ray radiation induced charging of defects in the gate dielectric. The induced charge can be neutralized and compensated if the graphene device is irradiated by X-rays at a negative gate voltage. Here the charge neutrality point shifts back to zero voltage. The observed phenomenon has strong implications for interpretation of X-ray based measurements of graphene devices as it renders them to significantly altered state. Our results also form a basis for remote X-ray tuning of graphene transport properties and X-ray sensors comprising the graphene/oxide interface as an active layer