Modern day electronic devices are reaching nanometer dimensions where atomistic effects are dominant. Present day chips have half a billion transistors, while scanning tips allow researchers to `see' and manipulate atoms and molecules to build interesting materials and devices. Fundamentally new principles are needed to understand how current flows at these nanometer length scales (1 nm ~ 10 atomic lengths), and traditional macroscopic concepts like mobility and diffusion coefficient need to be replaced by more basic concepts that require an understanding of resistance, `friction', and electron transport at their most fundamental level. Regardless of the specific form future electronic devices adopt, it is clear that we need to develop ways to describe and model the electronic properties of device structures engineered on an atomic scale. This is what our research is all about.

Specifically, our research focuses on three aspects of nanoelectronic modeling and simulation:

Fundamental physics of current flow through nanosystems:
Traditional CAD tools for electronic conduction are based on macroscopic concepts such as mobility and diffusion and continuum approaches such as effective mass theory, that do not apply at these length scales. We are exploring the novel physics arising from quantum interference, inelastic scattering, friction and heating due to vibrations and spins, strong non-equilibrium many-body effects, atomistic effects, nanoscale thermal and spin transport, hybrid electron dynamics at the nano-micro interface, as well as time-dependent effects due to hysteretic switching, memory and noise. Our aim is to understand these diverse physical phenomena, establish their formal evolution equations and predict/explain their experimental implications.

Computational modeling:
Next we translate the formal evolution equations into quantitative simulation tools, using a combination of computational materials science and quantum chemistry. This includes semi-empirical as well as first principles methods for capturing bulk and surface chemistry, interfacial bandstructure and transport, describing the nano-channels and contact surfaces atomistically. Special attention is aimed at multiscaling and embedding techniques to describe hetero-interfaces and surface states, as in hybrid molecule-silicon devices.

Device engineering:
Finally, we combine the formal equations with numerical simulation tools to identify performance advantages and limitations of nanoscale devices, such as resonant tunneling diodes, switches, conductors, interconnects, transistors and electronic sensors made out of various materials such as silicon or SiGe, molecules, nanotubes, nanowires, spintronic or magnetic elements and silicon quantum dots. Part of our current interests involve exploring hybrid devices operating on novel principles, such as gate-tunable scattering centers for characterization and detection, conformationally gated molecules for nano-relays, molecular redox centers and motors integrated on a silicon CMOS platform for memory and heat sinking.

Concrete research projects:

  • Molecular Electronics
  • Graphene based Electronics
  • Nanoscale characterization using Low-frequency noise
  • Nanoscale heat flow
  • Spin torque based random access memory
  • Non-equilibrium switching
  • Signal propagation in axonal systems
  • Multiscaling of transport properties
  • Computational modeling of interfacial bandstructure, chemistry and transport



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