ELECTRICAL AND COMPUTER ENGINEERING SEMINAR SERIES
Dr. Xudong Wang
Material Science and Engineering
University of Wisconsin
Thursday, April 12, 2018
3:00 p.m. - 4:00 p.m.
“Design and Synthesis of 1D and 2D Nanomaterials Away from Equilibrium”
Morphology is one essential element that gives rise to extraordinary physical, chemical, and mechanical properties in nanomaterials. Precise morphology control of nanomaterials is a notorious task, which heavily relies on fundamental understanding of the governing mechanisms and kinetics at the nanoscale. In this talk, I will present our three recent discoveries of the growth kinetics in 1D and 2D nanomaterial evolution. Firstly, the surface-reaction-limited pulsed chemical vapor deposition (SPCVD) technique will be discussed. The SPCVD technique effectively decouples the crystal growth from precursor vapor concentration, thus makes the conform growth of dense NW arrays inside highly-confined submicron-sized spaces possible. The evolution of NRs was found to be a manifestation of the Ostwald-Lussac Law. SPCVD opens a new route toward the design and creation of complex 3D hierarchical nanostructures, which can advantageously impact the devices performance of solar energy harvesting. Secondly, I will present our discovery of the wedding cake growth mechanism in the formation of 1D and 2D ZnO nanostructures. Within a narrow kinetic window, the surfaces of the 1D and 2D structures were covered with a unique concentric terrace feature, different from the screw-dislocation features. An interesting 1D to 2D morphology transition was found during the wedding cake growth, when the adatoms overcome the Ehrlich-Schwoebel (ES) barrier. At last, I will present a new ionic layer epitaxy (ILE) technique that uses surfactant monolayers to serve as soft templates guiding the nucleation and growth of 2D nanomaterials in large area beyond the limitation of van der Waals solids. One- to two-nm-thick, single-crystalline free-standing ZnO nanosheets with sizes up to tens of micrometers were synthesized at the water-air interface. ILE of other metals and oxides have also been proved to be successful.
Prof. Xudong Wang is a professor in the department of Materials Science and Engineering at University of Wisconsin – Madison. He received his PhD degree in Materials Science and Engineering from Georgia Tech in 2005. His current research interests include studying the growth mechanisms and developing assembly techniques of oxide nanostructures; developing advanced nanomaterials and nanodevices for mechanical energy harvesting from human activities and ambient environment; and understanding the coupling effect between piezoelectric polarization and semiconductor functionalities.
Faculty Host: Dr. Nelson Sepulveda (firstname.lastname@example.org)
Michigan State University is committed to providing equal opportunity for participation in all programs, services and activities. Accommodations for persons with disabilities may be requested by contacting Dr. Cagri Ulusoy (Ulusoy@msu.edu)