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Dr. Xiangfeng DuanDepartment of Chemistry and BiochemistryUniversity of California – Los AngelesHost: Professor Jun Xiao (MS&E)
Van der Waals Heterostructures, Superlattices and Thin Films: Boundless Opportunities at Bondless Boundaries
AbstractThe advent of two-dimensional atomic crystals (2DACs) and bonding-free van der Waals heterostructures has inspired a new thinking on heterostructure construction beyond the limits of traditional epitaxial heterostructures. In this lecture, I will discuss the exploration of van der Waals (vdW) interactions for heterogeneou integration of versatile heterostructures and superlattices with designable electronic interfaces. I start with a brief introduction the fundamental forces involved in vdW integration and some early background on using this approach for damage-free dielectric integration to enable high-speed transistors from atomically thin graphene and 2D semiconductors. Next, I will highlight our recent advancements in exploiting this approach for creating pinning-free metal/semiconductor junctions or photodiode approaching the Schottky-Mott limit or the intrinsic excitonic photophyiscs limit. Beyond simple heterostructures, I will discuss a broad family of vdW superlattices consisting of alternating 2D atomic layers and/or self-assembled molecular layers, with tailored structural symmetry, electronic band modulation and interlayer coupling as an artificial material platform for exploring emergent electronic, photonic, and exotic quantum phenomena; and introduce a unique design of vdW thin films that feature broad-area pinning-free vdW interfaces among the staggered nanosheets to ensure excellent electronic performance, and a sliding and rotation degree freedom to endow extraordinary mechanical stretchability, creating an exciting material platform for highly stretchable and adaptable electronic membranes. I will conclude with a brief perspective on exploring such artificial materials to unlock new physical limits and enable new device concepts beyond the reach of the existing materials.
BiographyDr. Duan received his B.S. Degree from University of Science and Technology of China in 1997, and Ph.D. degree from Harvard University in 2002. He was a Founding Scientist and then Manager of Advanced Technology at Nanosys Inc., a nanotechnology startup founded based partly on his doctoral research. Dr. Duan joined UCLA with a Howard Reiss Career Development Chair in 2008, and was promoted to Associate Professor in 2012 and Full Professor in 2013. Dr. Duan’s research interest includes nanoscale materials, devices and their applications in future electronic and energy technologies. Dr. Duan has published over 300 papers with nearly 90,000 citations, and holds >50 issued US patents. Dr. Duan has received many awards for his pioneering research in nanoscale science and technology, including MIT Technology Review Top-100 Innovator Award, NIH Director’s New Innovator Award, NSF Career Award, Alpha Chi Sigma Glen T. Seaborg Award, Herbert Newby McCoy Research Award, US Presidential Early Career Award for Scientists and Engineers (PECASE), ONR Young Investigator Award, DOE Early Career Scientist Award, Human Frontier Science Program Young Investigator Award, Dupont Young Professor, Journal of Materials Chemistry Lectureship, International Union of Materials Research Society and Singapore Materials Research Society Young Researcher Award, the Beilby Medal and Prize, the Nano Korea Award, International Society of Electrochemistry Zhao-Wu Tian Prize for Energy Electrochemistry, Science China Materials Innovation Award, AIP Horizons Lectureship, NanoMaterials Science Young Scientist Award, Materials Research Society Middle Career Researcher Award, International Union of Materials Research Society Frontier Materials Young Scientists Award, IEEE Nanotechnology Council Distinguished Lectureship, and most recently the IEEE Pioneer Award in Nanotechnology. He is currently an elected Fellow of Royal Society of Chemistry and Fellow of American Association for the Advancement of Science.