Dept. of Materials Science & Nanoengineernig
Exploring the Flatlands: Synthesis, Characterization and Engineering of Two-Dimensional Materials
Location: EB1 Room 1011
Friday, March 21st 2014 - 11:00 am
In this talk, we report the controlled vapor phase synthesis of MoS2 atomic layers and elucidate a fundamental mechanism for the nucleation, growth, and grain boundary formation in its crystalline monolayers. The atomic structure and morphology of the grains and their boundaries in the polycrystalline molybdenum disulfide atomic layers are examined and first-principles calculations are applied to investigate their energy landscape. The electrical properties of the atomic layers are examined and the role of grain boundaries is evaluated. More importantly, if precise two-dimensional domains of graphene, h-BN and MoS2 atomic layers can be seamlessly stitched together, in-plane heterostructures with interesting electronic applications could potentially be created. Here, we show that planar graphene/h-BN heterostructures can be formed by growing graphene in lithographically-patterned h-BN atomic layers. Our approach can create periodic arrangements of domains with size that ranging from tens of nanometers to millimeters. The resulting graphene/h-BN atomic layers can be peeled off from their growth substrate and transferred to various platforms including flexible substrate. Finally, we demonstrate how self-assembled monolayers with a variety of end termination chemistries can be utilized to tailor the physical properties of single-crystalline MoS2 atomic-layers. Our data suggests that combined interface-related effects of charge transfer, built-in molecular polarities, varied densities of defects, and remote interfacial phonons strongly modify the electrical and optical properties of MoS2, illustrating an engineering approach for local and universal property modulations in two-dimensional atomic-layers.
Jun Lou obtained B.E. and M.S. degrees in Materials Science and Engineering from Tsinghua University and Ohio State University, respectively, and his Ph.D. degree from the Department of Mechanical and Aerospace Engineering and Princeton Materials Institute at Princeton University. After a brief postdoc at Brown University he joined the Department of Mechanical Engineering and Materials Science at Rice University, and currently is an associate professor in the newly established Department of Materials Science and NanoEngineering. He is a recipient of the US Air Force Office of Scientific Research Young Investigator Award and the ORAU Ralph E. Powe Junior Faculty Enhancement Award. His research interests include nanomaterial synthesis, nanomechanical characterization and nanodevice fabrication for energy, environmental and biomedical applications.