Atomic-scale Observation of Grains and Grain Boundaries in Monolayers of WS2. (August 2014) - Azizi, Amin; Zou, Xiaolong; Ercuis, Peter; Zhang, Zhuhua; Laura Elias, Ana; Perea-López, Néstor; Terrones, Mauricio; Yakobson, Boris I.; Alem, Nasim