The is a renewal individual investigator award to two professors at the University of Massachusetts, Amherst. The primary objective of this project is to carry out an experimental investigation of charge transport through precisely-engineered, self-assembled molecular-scale electronic devices. The recently identified phenomenon of electromechanical charge shuttling is expected to play a significant role in these nanodevices -- in particular, because these devices have parts that can move and vibrate. This project utilizes a device fabrication approach that integrates recently developed molecular recognition assembly techniques used in chemical research with electron-beam lithographic methods used in microelectronics research. Thymine/diaminotriazine molecular recognition pairs will be used to position a nanometer-scale particle midway between closely-spaced lithographic electrodes. To explore the interplay of charge shuttling and single-electron charging effects, transport characteristics will be compared for devices using "hard-spring" and "soft-spring" organic bridging molecules. Single-electron transistor behavior will be investigated with the use of a capacitive gate electrode. The project also includes investigations on shuttle dynamics at the macroscopic scale, since much fundamental understanding can be revealed through experiments on larger-sized shuttle devices. This research is likely to impact the development and understanding of a variety of systems: nanodevices made of soft/hard composites, flexible nanosystems, microelectromechanical (MEMS) devices, specific biological systems, and even particular macroscopic devices. This research project will provide training for graduate students and post docs in state-of-the-art techniques and concepts in this interdisciplinary field involving condensed matter physics and chemistry. This training will prepare the students for careers in academe, industry, or government laboratories. %%% Miniaturization technology has resulted in smaller, more powerful computers, smarter handheld devices, and gadgets of increased functionality. However, we are rapidly approaching the limit where the continued miniaturization of microelectronic devices by standard techniques will proceed no further. As a consequence it is crucial to develop reliable methods to create a class of devices at the molecular-size scale. This is a renewal award to two investigators at the University of Massachusetts, Amherst to follow the robust example set by nature itself - to construct nanometer-scale structures by exploiting self-assembly based on molecular recognition. In this project, novel single-electron transistor devices are self-fabricated in a fashion that mimics the way in which biological molecules are able to recognize other specific molecules. These devices are expected to carry electricity by an unusual means that involves electrons which are "shuttled" from one place to another. This research is likely to impact the development and understanding of a variety of systems: hybrid nanodevices made of molecules and nanoparticles, flexible nanosystems, microelectromechanical (MEMS) devices, specific biological systems, and even particular macroscopic devices. This research project will provide training for graduate students and post docs in state-of-the-art techniques and concepts in this interdisciplinary field involving condensed matter physics and chemistry. This training will prepare the students for careers in academe, industry, or government. ***
