Defect Engineering and Patterning of Thin Films and Two-Dimensional Materials: A Computational Materials Science Approach
Department of Chemical Engineering, University of Massachusetts, Amherst
Defect engineering of nanomaterials and metamaterial structures, in conjunction with chemical functionalization, is a most promising route for developing new materials with unique properties and function. Moreover, the ability to drive pattern formation on material surfaces by applying and precisely controlling macroscopic external forces, such as mechanical stress and electric fields, can have major fundamental and technological impact on improving materials function and reliability and developing innovative, directed-assembly processes for nanotechnology. Toward these goals, multiscale computational materials science has emerged as a systematic approach for designing new materials and enabling new nanofabrication technologies.
In this seminar, we focus on superstructures of diamond nanocrystals (SDNs) embedded between the graphene planes of twisted bilayer graphene, synthesized by patterned chemical functionalization of graphene bilayers. We demonstrate the tunability of the electronic band gap, mechanical properties, fracture behavior, and thermal transport properties of SDNs achieved by precise control of the extent and pattern of chemical functionalization. In addition, we address problems of surface morphological instabilities in biaxially stressed thin films used in electronic and nanofabrication technologies. We demonstrate the precisely controlled formation of multiple quantum dots (QDs), or QD molecules, by exploiting a nonlinear film surface morphological instability due to the lattice mismatch between the film and substrate materials, and show how QDs can be transformed to nanorings as a result of thermal annealing due to the thermal mismatch between the film and the substrate. We also explore strategies for the growth of ordered patterns of quantum dots and nanorings on films grown epitaxially on pit-patterned substrates.
- 10:30 Refreshments
- 10:45–12:00 Talk