Theses Doctoral

Single-Molecule Transistor from Graphene Nanoelectrodes and Novel Functional Materials From Self-assembly

Xu, Qizhi

This thesis introduces a new strategy to fabricate single molecular transistor by utilizing the covalent chemistry to reconnect the molecule with the electroburnt graphene nanogap. We studied the effect of coupling chemistry and molecular length on the efficiency of reconnection between the molecule and the graphene. With this technique, we are also able to observe the Coulomb Blockade phenomenon, which is a characteristics of single-electron transistors. The high yield and versatility of this approach augur well for creating a new generation of sensors, switches, and other functional devices using graphene contacts. This thesis also introduces a new type of organic single-crystal p-n heterojunction inspired from the ball-and-socket shape-complementarity between fullerene and contorted dibenzotetrathienocoronene (c-DBTTC). We studied the influence of temperature, pressure, and time on the self-assembly process of contorted dibenzotetrathienocoronene on the as-grown fullerene crystals. We also utilized fluorescence microscopy to investigate the charge transfer in this type of p-n heterojunction. Finally, this thesis introduces one-dimensional and two-dimensional programming in solid-state materials from superatom macrocycles. We find that the linkers that bridges the two superatoms determine the distance and electronic coupling between the two superatoms in the macrocycle, which in turn determines the way they self-assembled in the solid-state materials.
The thesis is composed of four chapters. The first chapter introduces why we are in terested in molecular transistors and new functional materials, and what has been done so far. The second chapter described the approach we developed to assemble single molecule into circuits with graphene electrodes. The third chapter details the method to fabricate the organic single-crystal C60-DBTTC p-n heterojunction, which is of great importance to understand their charge transfer process. The last chapter introduced a new series of superatom macrocycles and their self-assembly into solid-state materials with electron acceptor tetracyanoethylene.


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More About This Work

Academic Units
Thesis Advisors
Nuckolls, Colin
Ph.D., Columbia University
Published Here
August 20, 2017