Electron Flow in Semiconductor and Molecular Nanostructures

The main avenues of experimental research being pursued in various laboratories to build future generations of smaller/faster devices are (i) down sizing of conventional semiconductor devices and (ii) molecular devices.

In a large number of these structures, the length scales and transit times are comparable to the wavelength of the electrons and the scattering times. The focus of my research is to understand and characterize transport through molecular and semiconductor nanostructures. Below are brief descriptions of these two items.

Please visit my publication page for reprints or contact me at anant@nas.nasa.gov, for more information.

2D quantum simulations

Our aim is to investigate the influence of the wave nature of electrons on the electronic properties of ultra small structures / devices. We have developed a set of approximations and state of the art computer code to study the following (1D approximations are not made): * I_d vs. V_g and I_d vs. V_d characteristics for ultra small MOSFETs
* Short channel effects
* Ballistic effects
* Gate leakage current
* Benchmark semi-classical methods that include quantum effects in MOSFETs without significant increase in simulation time.

Further, our code can handle a wide variety of 2D doping profiles and anisotropic effective mass within the parabolic approximation. The equations we solve are the Non Equilibrium Green's Function and Poisson's equations.

This work is done in collaboration with T. R. Govindan and Alexei Svizhenko. Outside collaborators: Ramesh Venugopal (Purdue University), Mark Lundstrom (Purdue University)

For more information on this project contact anant@nas.nasa.gov

Molecular Structures

Our work at this time is focused on carbon nanotubes and DNA. We are using a combination of tight-binding and quantum chemistry methods to study various aspects of current flow in these structures:
* Current-carrying capacity of nanotubes
* Coupling between molecules and metal contact
* Effect of uniaxial strain in nanotubes
* Transport in deformed nanotubes and DNA
* Nanotubes with end groups (other molecules)

Our work in this area has so far used a simple pi orbital tight-binding approach. Based on the numerical expertise we have developed in "2D quantum simulations" in semiconductor nanostructures, we are now extending this frame work to include molecular nanostructures.

This work is done in collaboration with Christophe Adessi, T. R. Govindan, Jie Han, Alexei Svizhenko and Liu Yang. Outside collaborators: James O' Keefe (Stanford University)