ABSTRACT: The isolation of graphene, now over decade ago, has given rise to the revitalization of an old full set of materials, two-dimensional materials (2DM), which have exceptional electrical, chemical and physical properties. Some of the materials under investigation in addition to graphene are hexagonal boron nitride (h-BN), semiconducting, metallic, and superconducting, transition metal dichalcogenides (TMD) with a general chemical formula, MX2 where M is for example equal to Mo, W, Ta, Nb, Zr, Ti, and X = S, Se and Te, and others. While graphene is a material with many exceptional properties and h-BN is an excellent 2D insulator, TMD materials provide what neither graphene nor h-BN can, bandgap engineering that, in principle, can be used to create new devices that cannot be fabricated with h-BN and graphene alone. There is hope that 2DM can be integrated to fabricate numerous device types for many applications ranging from inkjet-printed circuits, photonic applications, flexible electronics, and high-performance electronics. However, in order to fully realize the benefits of these materials, the community will have to work together to define the device structures, device integration schemes, and materials growth processes and requirements.
A number of deposition techniques have been used to prepare large area graphene, such as growth on SiC through the evaporation of Si at high temperatures, precipitation of carbon from metals, and chemical vapor deposition on Cu. Direct growth of good quality graphene on dielectrics/semiconductors other than SiC with reasonable properties has only been reported recently on Ge. The preparation of large area h-BN is also in great demand and processes are being developed to achieve this on both metals and dielectrics. Transition metal dichalcogenides present altogether different opportunities and difficulties in the preparation of low defect density large area single crystals. Vapor transport, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE) are being developed to produce these materials for initial studies of materials physics device fabrication. In addition, there is some effort in performing simulations to guide growth for both CVD and MBE growers. Therefore, there is an opportunity here to have the crystal growers and the modeling community collaborate to develop high quality materials and processes.
A number of devices structures are currently under evaluation to take advantage of the basic properties of graphene, bi-layer graphene, h-BN and TMDs. Some of the devices are based on tunneling phenomena while others are based on excitonic phenomena. In this presentation I will present the state of the art results of graphene, h-BN, and a few TMD materials and their prospects for future electronic device applications.
BIOGRAPHY: Dr. Luigi Colombo earned BS (1975) degree in Physics from Iona College (NY) and PhD (1980) degree in Materials Science from the University of Rochester (NY). He is now an Adjunct Professor of Materials Science & Engineering at the University of Texas at Dallas after a 36-year career at Texas Instruments (TI). He joined TI in 1981 to work on infrared detector materials where he performed research on II-VI compounds, and developed a HgCdZnTe liquid phase epitaxy process and put in production in 1991; this process is still in production today. Luigi has also developed high-k capacitor MIM structures for DRAMs, SiON/poly-Si and Hf-based high-k gate/metal transistor gate stacks for advanced transistor devices beyond the 90 nm node. In the last 10 years or so he was responsible for the development of new materials such as graphene, hexagonal boron nitride and transition metal dichalcogenides and their integration in new device flows as part of the Nanoelectronics Research Initiative (NRI). Luigi has developed the first CVD graphene process on Cu in collaboration with researchers at UT Austin. He has authored and co-authored over 150 refereed papers, made over 170 invited and contributed presentations, has written 4 chapters in edited books, and holds over 100 US and international patents. He is on the Strategic Advisory Council of the European Graphene Flagship, has been on the advisory board of the UC Berkeley Center for Energy Efficient Electronics Science External Advisory Board, the SRC-NRI Technical Program Group, and the SRC-STARnet Strategic Advisory Board. He was a TI Fellow, and is an IEEE and APS Fellow.