N. Swami, L. Harriott, Electrical Engineering, University of Virginia (UVA)
The interconnection of molecular device layers presents a major challenge to the realization of circuits based on molecular electronics. The objectives of this research are to develop strategies for the construction of high-yield interconnected polymer-molecular device junctions through controlled deposition and patterning of contact layers, and devise pathways for the vertical integration of molecular devices into useful circuits. The approach to pattern contact layers is through selective deposition on molecular device layers or selective removal from layers without active device layers, thereby enabling molecular devices with independently addressable arrays of top and bottom contacts that may be integrated vertically to form high-density circuits.
Intellectual Merit: Intellectual merits of the work include the enabling of better interconnection strategies through the improvement of device yield; the capability to conduct studies on chemical stability, electromigration, and molecular conformation changes within a device junction; and the development of device structures that are compatible with vertical integration. Since molecular electronics is seen as a viable alternative to next-generation CMOS-compatible nanoelectronic circuits, the development of interconnection strategies is crucial to its adoption.
Broader Impacts: Broader educational impacts include an understanding of the limits of electronic coupling to molecular device layers from stable polymer contacts, and addressing signal integration of molecular devices with CMOS circuits. One Ph.D. student will be supported for this work, and educational content from this research will be integrated into distance education courses on Nanoelectronics, Nanofabrication and Nano-device characterization.
Molecular device junctions are currently on the International Technology Roadmap for Semiconductors as viable alternatives for application within specialized next-generation nanoelectronic circuits that may require higher device densities, selective conformational state properties, and surface-modulated charge control. In this project, we focused on the fabrication, characterization and interconnection of molecular device junctions for interfacial charge control due to molecular conformation or dipoles. Within follow-up supplements to the award, we applied polymer nanofabrication towards fields other than molecular device junctions, such as: biomaterials and microfluidics. Intellectual Merits: Interfacial charge modulation is an essential feature for switching within field effect transistors in information processing and sensing. Device scale-down causes poor control of threshold voltage variations. We developed molecular layers that offer electronic tunability (for charge modulation) and self-assembly. The charge-modulation within these devices was based on molecular conformation changes or induced dipoles. Additionally, we established preliminary schemes for interconnection of molecular device junctions. Methodology: We developed the following methods towards this vision: • Soft lithography contact fabrication to molecular layers • Electrical characterization of molecule-induced dipoles • Strategies for interconnection of molecular devices Broader Impacts: The technological and societal impacts from this award include: •Improving reproducibility of switching within high-sensitivity nanoscale devices • Improving reliability of molecular junctions • Distance education course developed on Nanoelectronics and Nanofabrication • Training 2 Ph.D. students to degree completion: 1 International (Ms. Fernanda Camacho-Alanis) and 1 US citizen woman student (Ms. Emma Fauss) • International collaboration with Academia Sinica, Taiwan, for polymer nanofabrication for devices in molecular electronics, tissue regeneration and microfluidics A number of research articles and conference presentations diseminated the advances t the broader scientific comunity. Refereed Journal Publications (1) L. Wu, F. Camacho-Alanis, G. Zangari, N. Swami; "Electrical contacts to molecules: electroless deposition for fabrication of top contacts to molecular devices on semiconductors", ECS Transactions, Chicago, Volume 6, New Bioanalytical and Biomedical Methods (2007). (2) "Molecular junctions of ~1 nm device length on self-assembled monolayer modified n- vs. p-GaAs", F. Camacho-Alanis, L. Wu+, G. Zangari, N. Swami*, Journal of Materials Chemistry, 18, 5459-5467 (2008). http://pubs.rsc.org/en/Content/ArticleLanding/2008/JM/B811395E Journal Impact Factor = 4.34 Times Cited: 13 (3) "Electrolytic Gold Deposition on Dodecanethiol-Modified Gold Films." G. Pattanaik, W. Shao, N. Swami, G. Zangari*. Langmuir. (2009), 25, pp 5031–5038. Journal Impact Factor = 4.1; Times Cited: 4. http://pubs.acs.org/doi/abs/10.1021/la803907p (4) "Fabrication and characterization of interconnected molecular devices in a nanowell crossbar architecture", Z. Martin, N. Majumdar, M. Cabral, F. Camacho-Alanis, N. Gergel, N. Swami*, L. Harriott, Y. Yao, J. Tour, D. Long, R. Shashidhar, IEEE Trans. Nanotechnology (2009) 8, 574-581. http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4907067 . Journal Impact Factor = 2.0; Times Cited: 3 (5) "Electrochemical impedance spectroscopy of carboxylic-acid terminal alkanethiol monolayers on GaAs of varying substrate doping", L. Wu, F. Camacho-Alanis, H. Castenada, G. Zangari, N. Swami*, Electrochimica Acta (2010) 55, 8758–8765. Journal Impact Factor = 3.56; Times Cited: 7. http://dx.doi.org/10.1016/j.electacta.2010.08.001 (6) "Electrochemical Impedance Spectroscopy for Probing Semiconductor Surface Charge Modulation through monolayer de-protonation", F. Camacho- Alanis, H. Castenada, G. Zangari, N. Swami*, Langmuir (2011), 27, 11273-11277. Journal Impact Factor = 4.1. Times Cited = 1. http://pubs.acs.org/doi/abs/10.1021/la2013107 Supported by Award Supplement (1) "Photoelectrochemical Stability of Electrodeposited Cu2O Films", Lingling Wu, Lok-kun Tsui, Nathan Swami, Giovanni Zangari*, Journal of Physical Chemistry C (2010) 114, 11551-11556. Journal Impact Factor = 4.22 Times Cited: 18 http://pubs.acs.org/doi/abs/10.1021/jp103437y (2) "Interplay of electrical forces for alignment of sub-100 nm electrospun nanofibers at insulator gap collectors", V. Chaurey, P. Chiang, C. Polanco, R. Su, C.F. Chou, N. Swami*. Langmuir (2010), 26 (24), pp 19022–19026. http://pubs.acs.org/doi/abs/10.1021/la102209q Journal Impact Factor = 4.1; Times Cited: 12 (3) "Floating electrode enhanced constriction dielectrophoresis for trapping of nanoscale biomolecules in high-conductivity media", V. Chaurey, C.F. Polanco, C.F. Chou, N. Swami*, Biomicrofluidics (2012) 6 (1), 012806. Journal Impact Factor = 3.5; Times Cited: 9 DOI: 10.1063/1.3676069; http://link.aip.org/link/doi/10.1063/1.3676069 (4) "Nano-constriction device for rapid protein pre-concentration in physiological media by electrokinetic force balance", K.T. Liao, M. Tsegaye, V. Chaurey, C.F. Chou, N. Swami*. Electrophoresis (2012), 33, 1958-1966. Journal Impact Factor =3.3; Times Cited: 5. DOI: 10.1002/elps.201100707 www.ncbi.nlm.nih.gov/pubmed/22806460 (5) "Nanofiber size-dependent sensitivity of fibroblast directionality to the methodology for scaffold alignment", V. Chaurey, F. Block, R. Su, P. Chiang, E.A. Botchwey, C.F. Chou, N. Swami*, Acta Biomaterialia (2012), 8, 3982–3990. Journal Impact Factor = 4.865 http://dx.doi.org/10.1016/j.actbio.2012.06.041 (6) "Scaling down constriction-based dielectrophoresis for trapping nanoscale biomolecules in high conductivity media", V. Chaurey, A. Rohani, Y.-H. Su, W. Varhue, K.T. Liao, C. F. Chou, N. S. Swami*, Electrophoresis (2013), 34, 1097-1104. Journal Impact Factor =3.3 We envision that these methodologies will be applied within future advances in nanoelectronic circuits, micro/nanofluidics for biosensing and tissue regeneration.
