Browsing by Author "Sagade, Abhay A."

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    Graphene-based nanolaminates as ultra-high permeation barriers
    (Nature Publishing Group, 2017-10-23) Sagade, Abhay A.; Aria, Adrianus Indrat; Edge, Steven; Melgari, Paolo; Gieseking, Bjoern; Bayer, Bernhard C.; Meyer, Jannik C.; Bird, David; Brewer, Paul; Hofmann, Stephan
    Permeation barrier films are critical to a wide range of applications. In particular, for organic electronics and photovoltaics not only ultra-low permeation values are required but also optical transparency. A laminate structure thereby allows synergistic effects between different materials. Here, we report on a combination of chemical vapor deposition (CVD) and atomic layer deposition (ALD) to create in scalable fashion few-layer graphene/aluminium oxide-based nanolaminates. The resulting ~10 nm contiguous, flexible graphene-based films are >90% optically transparent and show water vapor transmission rates below 7 × 10−3 g/m2/day measured over areas of 5 × 5 cm2. We deploy these films to provide effective encapsulation for organic light-emitting diodes (OLEDs) with measured half-life times of 880 h in ambient.
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    Parameter space of atomic layer deposition of ultra-thin oxides on graphene
    (American Chemical Society , 2016-10-10) Aria, Adrianus Indrat; Nakanishi, Kenichi; Xiao, Long; Braeuninger-Weimer, Philipp; Sagade, Abhay A.; Alexander-Webber, Jack; Hofmann, Stephan
    Atomic layer deposition (ALD) of ultrathin aluminum oxide (AlOx) films was systematically studied on supported chemical vapor deposition (CVD) graphene. We show that by extending the precursor residence time, using either a multiple-pulse sequence or a soaking period, ultrathin continuous AlOx films can be achieved directly on graphene using standard H2O and trimethylaluminum (TMA) precursors even at a high deposition temperature of 200 °C, without the use of surfactants or other additional graphene surface modifications. To obtain conformal nucleation, a precursor residence time of >2s is needed, which is not prohibitively long but sufficient to account for the slow adsorption kinetics of the graphene surface. In contrast, a shorter residence time results in heterogeneous nucleation that is preferential to defect/selective sites on the graphene. These findings demonstrate that careful control of the ALD parameter space is imperative in governing the nucleation behavior of AlOx on CVD graphene. We consider our results to have model system character for rational two-dimensional (2D)/non-2D material process integration, relevant also to the interfacing and device integration of the many other emerging 2D materials.