Azad Naeemi, Ph.D. - US grants

The objective of this research is to develop methods to characterize and control edge scattering in graphene nanoribbons (GNRs). The approach is (i) to optimize patterning of narrow-width GNRs, (ii) characterize size-effect in narrow-width GNRs, and (iii) reduce edge scattering by using a combination of surface and edge chemistry.

Intellectual merit: Graphene has been found to have a variety of interesting and superior properties suitable for post-CMOS nanoelectronics. Long mean free paths and very high mobility have been demonstrated in large-area graphene. With dimensional scaling, edge scattering in GNRs leads to a significant degradation in carrier transport, it was recently demonstrated by the proposing principal investigators that edge scattering sets in at widths of around 60 nm. Extending the superior properties of graphene to GNRs is important for a number of nanoelectronics applications since it allows for fast switching, quantum coherent devices, and high device density. The techniques proposed in this work will hasten the implementation of graphene for various charge-based as well as alternative state variable switches and interconnects.

Broader impact: Education will be an important component of the proposed work the PIs regularly involve undergraduates and minorities in their research as part of summer internship programs. Graduate and undergraduate students involved in this research will get trained on advanced fabrication and characterization techniques. The PIs' also involve a number of teachers as part of research experience for teachers (RET) programs. The PIs' labs are a regular part of tours to middle- and high-school children.

The objective of this program is to develop experimentally-validated physical models for graphene interconnects and to optimize and benchmark them against conventional metallic interconnects. The proposed research will model and experimentally validate: high-frequency signal propagation in mono- and multi-layer graphene nanoribbons; impact of contact shape and size, interconnect length and width, and edge quality on current distribution in multilayer graphene nanoribbons; and crosstalk noise and line-to-line interference amongst graphene nanoribbons.

The intellectual merit is to provide the first unified electromagnetic/quantum mechanical model to analyze high-frequency signal transport in nanomaterials in general and in multilayer graphene interconnects in particular. Existing full-wave electromagnetic field simulators cannot capture the multi-physical nature of signal transport in nanomaterials. Crosstalk in nanoconductors such as graphene is fundamentally different than in conventional metallic wires. This is because the voltage applied to the neighboring interconnects would shift the Fermi energy of the victim line which would affect the victim?s conductance.

The broader impacts are: to create a new paradigm in teaching electron transport by developing a video game in which players navigate electrons or holes in a crystal and get to visualize and experience the key concepts in the physics of semiconductors; to engage undergraduate students taking Physics of Semiconductors to think creatively about the course materials and to create game scenarios aimed at learning various physical concepts; and to adopt the video game for K-12 students, their teachers, and the public, and for outreach activities to attract underrepresented minorities to engineering.

Proposal: ECCS-1626153
PI: Oliver Brand
Institution: Georgia Tech Research Corporation
Title: NNCI Coordinating Office at Georgia Tech


Abstract

The National Nanotechnology Coordinated Infrastructure (NNCI) comprises 16 university sites and their partners awarded individually by the National Science Foundation to provide open access to nanoscale fabrication and characterization user facilities and staff expertise across the nation. The NNCI Coordinating Office at Georgia Tech is established to enhance the impact of NNCI as a national infrastructure network by promoting its capabilities, facilitating user access to its resources, sharing best practices, and improving overall efficiency through coordination of activities of the individual sites. The Coordinating Office will assist users from academe, industry, and government in finding NNCI fabrication and characterization resources to meet their research needs through an interactive NNCI web portal. It will use the expertise of site staff to facilitate programs in education and outreach, social and ethical implications, and computational modeling and simulation across the network, and help provide linkages with other national and international nanotechnology resources. The overall activities of the NNCI Coordinating Office will contribute to the economic competiveness of the U.S. in training a globally competitive workforce and in providing efficient access to resources for innovation and commercialization of nanotechnology. They will also help to inform and educate the general public on fundamentals and advances of nanoscience and engineering and their social and ethical implications.

The mission of the NNCI Coordinating Office is to support the individual NNCI sites, site users, and broader public interests using the combined assets of a nation-wide network of university nanotechnology user facilities. A key component of the Coordinating Office will be the development of mechanisms for communicating availability of network assets to users of the facilities as well as for fostering interactions among the sites. A primary mode for this communication will be an interactive NNCI web portal, which will allow new and existing users to efficiently locate capabilities and expertise within the network, and also provide up-to-date nanotechnology resources to the K-20 communities and broader public. To emphasize the importance of a network of sites, the Coordinating Office will be guided by an Executive Committee with representation from all 16 sites and will organize a number of working groups and committees to address topics of broad interest and solve common problems. A flagship event for the NNCI network will be an annual NNCI Conference that will highlight the research supported by the individual sites, as well as provide a venue for site staff to share best practices and research trends with the broader nanotechnology community. An External Advisory Board with members selected from the external advisory boards of all sites will provide input on network management issues and future directions. Education and outreach activities will be coordinated across the network to share and disseminate best practices and resources for impactful programs at the local, regional, and national levels. Social and ethical implications programs, such as an annual retreat and conference forums, will enable social scientists to interact with nanoscale scientists, engineers, and students so that all groups can consider the potential impacts new discoveries might have on society. Computational modeling and simulation needs of the user community will be supported through an inventory of available resources and close collaboration with the existing Network for Computational Nanotechnology (NCN). Assessment of the strength of the sites and the network as a whole will be determined through metrics developed in collaboration with the sites and will be based on site usage, site productivity and technical impact, contributions to the network, and education and outreach activity.

There is a critical need for new technologies as the semiconductor industry reaches the limits of how small a transistor can be made and how much power can be used in an increasingly small space. This project will meet this need through the development of novel memory and logic devices. Continual interaction between academia and the semiconductor industry will ensure in new semiconductor device concepts that lead to faster and better electronics that use significantly less energy than current approaches. These advances will exploit the unusual magnetic properties of magnetoelectrics, a special class of materials that tie together magnetism and voltage. An important aspect of the devices will be their nonvolatility, a feature that makes them prime candidates for use in the emerging Internet of Things. Nonvolatility refers to the property that once written, information can be recovered, even if electrical power has been absent for an extended period. An example of such a situation is the shutdown of a computer. A computer equipped with this type of "instant on" circuitry will restart to the exact state when power failed. Nonvolatility will also lead to energy savings by enabling electronics to operate longer on smaller batteries with less need for recharge. Reducing the energy cost of consumer electronics could also lead to some world-wide energy savings, as new less energy expensive electronics become available.

This project develops novel device concepts to greatly extend the practical limits of energy-efficient computation, focusing primarily on magnetoelectric materials, enabling interfacial magnetism to be reversibly switched by voltage. This approach to the writing of magnetic information via voltage will result in a significant reduction in energy consumption, while improving the computing speed of integrated circuit technologies. To enable electronic applications based on these devices to come to fruition, the new concepts must allow for miniaturization, inexpensive fabrication on a huge scale, and long working lifetimes. Just as for conventional electronic circuits, to ensure reliable operations, the new devices will be capable of operating repeatedly at well above room temperature. By exploiting more than just electrical charge in each device, these new devices will have more function than a simple transistor, which in turn, will present new opportunities for the development of circuit ideas that go beyond existing technologies ? ideas that will also be explored as this research program develops.