NSF- NIRT: "Surface State Engineering" Charge Storage and Conduction in Organo-Silicon Heterostructures as a Basis for Nanoscale Devices John C. Bean (PI) 1, Avik Ghosh 1, Lloyd R. Harriott 1, Lin Pu 2, Keith Williams 3 1 Department of Electrical and Computer Engineering, 2 Department of Chemistry, 3 Department of Physics University of Virginia, Charlottesville Virginia Basic Idea: Create highly-pure, highly-ordered bound organo-silicon hybrids Molecules bound so intimately that electron waves pass easily between components Yielding: 1) Precise charge transfer into and out of Si surfaces 2) Conduction based on quantum mechanical resonance In nanoscale MOSFETs this could: 1) Supplant trace donor/acceptor charge creation 2) Minimize ionized impurity scattering => Enhanced transport 3) Enable devices based on quantum interference phenomenon Dual pronged first year NIRT strategy: CNT FET experiments to hone characterization + modeling tools Parallel development of full quasi 1D Molecular-SOI FET “Fingerprinting” of Charge Centers in CNT FETs Based on phenomenon of “random telegraph signals” (RTS): In quasi 1D FET, charged trap can act as gate As that charge center charges & discharges, FET current flickers Details of flicker vs. FET bias => Spectroscopy of charge centers? Quasi 1D FET realized with carbon nanotube: Yielding “classic” And a form of RTS signal single Level RTS:not previously observed Explaining newly observed CNT RTS signals As effect of two closely spaced charge centers Preparing for full Molecular-SOI FET device where: MOST exposed Si surface sites must first be molecularly passivated So SELECTED sites can then be molecularly activated Molecular attachment to Si measured with ATR-FTIR Molecular passivation of Si measured using pulsed photoconductance: Passivation  Minimal surface recombination  Maximum carrier lifetime State-of-the-art passivation demonstrated for acetylene attached via UV-hydrosilylation: Completing toolset necessary to meet up with... Parallel development of full FET device structure Side-gated Silicon on Insulator FET: Side gated design to vary effective channel width Based on double lift-off e-beam patterning New e-beam system acquired and installed Contact metallization and resists developed Key sub-structures recently produced: Now in process of combining these into full SOI FET Device Which will then be ready to test molecular passivation & activation + Education and Outreach building upon: 1999 NSF CCLI => “UVA Virtual Lab” Science Education Website Website traffic now approaching 4.5 million hits! ( NSF NUE => “Hands-on Introduction to Nanoscience” Class Our VR recreation of class's AFMs and STMs Together => 2009 IEEE Undergraduate Teaching Medal To bring Nanoscience into Virginia Public Schools: - Helped Danville CC create and fund Nano curriculum Including successful grants to build their own ATM / STM lab - Worked with Science Museum of Virginia to develop Nano exhibits - Created for K-12 teacher workshop / class on teaching Nano: For which teachers received UVA credits With ongoing follow-up activities Addressed by Multiscale Modeling: Coupling weak and strong quantum correlation (wires vs. dots): Density Functional Theory (Si) / Extended Hückel (molecules) Within framework of Non-Equilibrium Green's Functions Applied to molecular SURFETs data: Successfully modeling observed threshold shifts as: Vasudevan et al, IEEE-Sens. ’08 and Cond-Mat ‘08 Validated modeling techniques then applied to our CNT RTS data Aluminum channel side gates with 92 nm gap 50 nm wide silicon on insulator channel 29 nm wide silicon on insulator channel Tour et al (JACS 2006) J.Chan et al, in review Acetylene / Si Thermal Oxide / Si Native Oxide / Si } 500 uSec Photocunductance