Presented by Xiaogan Liang, Ph.D, Assistant Professor
Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, U.S.A
Time：3:00 p.m.,July 4,2013.
One of the most exciting and important research directions of graphene and other emerging atomically layered 2D materials is to investigate how nanopatterning technologies can be adapted, developed, and refined to pattern 2D material films into nanostructures, aiming to obtain the desirable electronic characters and functionalies that could significantly leverage the unique property or potential of these 2D materials. In this talk, Xiaogan Liang present an upscalable nanolithographic method for patterning orderly arranged sub-10 nm half-pitch graphene nanoribbons (GNRs) and fabricated field-effect transistors (FETs) bearing such densely arranged GNRs. The nanofabrication method combines nanoimprint lithography (NIL), directed self-assembly of block copolymers, and plasma etching. Their work shows that the standard variation of the ribbon width (3σ value) among densely arranged GNRs strongly depends on the processing condition of directed self-assembly of block copolymers, and it can significantly affect the ON/OFF current ratio of the FETs bearing multiple GNR channels. A relatively large 3σ variation of the ribbon width can result in a poor ON/OFF current ratio, which is attributed to the non-synchronization of OFF states of multiple nonuniform GNRs. Through the processing optimization, they are able to create 8 nm hp GNRs with 3σ width variation less than 3 nm. The FET bearing 200 such GNRs exhibits a relatively high ON/OFF current ratio > 10. The nanofabrication method presented in this work could be further developed to realize nanomanufacturing of high-quality graphene nanostructures for future scale-up nanoelectronic applications. In addition, their work provides critical insights for the further optimizing the electronic properties of graphene nanostructures.
In addition,Xiaogan Liang will also present their recent work on plasma-assisted transfer-printing of MoS2 micro-/nanostructures into ordered arrays over cm2-scale areas. The MoS2 patterns printed on plasma-charged substrates feature a regular edge profile faithfully correlated to prepatterned structures on bulk stamps. Furthermore, they have successfully fabricated working transistors based on printed MoS2 pixels, which exhibit excellent transport properties. Their transfer-printing method could be generalized for massively producing other emerging 2D nanostructures and lay an important foundation for future scale-up applications of MoS2 and graphene micro- and nanostructures.
Dr. Xiaogan Liang is currently working as an Assistant Professor at The Mechanical Engineering Department of University of Michigan (UM). Before joining UM, Dr. Liang was a Staff Scientist (PI) working at The Molecular Foundry, Lawrence Berkeley National Laboratory. His current research interests are focused on nanoimprint/nanoprint lithography, nanoelectronics based on low-dimensional nanostructures, nanofluidics, and block copolymer self-assembly. Dr. Liang has coauthored 35 journal publications and more than 30 conference presentations, and has 3 US patents and 6 pending patents. Xiaogan Liang is the member of Sigma Xi, IEEE, and MRS.Dr. Liang obtained a BS in Physics from Peking University, a MS in Condensed Matter Physics from Chinese Academy of Sciences, and a Ph.D. in Electrical Engineering from Princeton University.