Physics & Astronomy ETDs


Anita Parmar

Publication Date



The beginning of this century saw the pioneering fabrication of a single molecular transistor using a single C60 molecule between gold nanowires, and inspired experimentalists and theorists alike to focus on studying phonon assisted transport through nanoscale electronic devices. We have formulated an electron tunnelling model for the current-voltage (I-V) relationship for a C60 molecular transistor that reproduces trends observed in the experimental I-V curves. A uniform one dimensional tight-binding lattice is used to model the transistor system, with a central defect site representing the molecule. The current is written as a function of tunnelling rates on and off of the molecule, where the rates are calculated using Fermi's Golden Rule and a Green function technique called the Renormalized Perturbation Expansion. In calculating the tunnelling rates, a deeper understanding of the trends that are seen in the experimental data is attained, and certain new features of the system are uncovered. First, incorporating the degeneracy of the tunnelling state into the expression for the current allows the prediction of the degree of asymmetry in the saturation values for forward and reverse bias current. Also, using the relative sizes of the source-drain voltage gaps for forward and reverse bias current, and the relative sizes of the initial steps in current, we show that the C60 molecule is negatively charged when in a nanometre sized gap between two gold nanowires. Finally, an experimental method for measuring the effect that varying the gate voltage has on the size of the voltage gap between the tunnelling level of the molecule and the Fermi level of the electrodes is obtained.

Degree Name


Level of Degree


Department Name

Physics & Astronomy

First Advisor

Dunlap, David H.

First Committee Member (Chair)

Prasad, Sudhakar

Second Committee Member

Kenkre, V.M.

Third Committee Member

Grey, John




Molecular integrated circuits--Mathematical models, Electron-phonon interactions--Mathematical models, Tunneling (Physics)--Mathematical models, Green's functions, Nanoelectronics.

Document Type