NIRT: Semiconducting Nanowires: Novel Phenomenon and Nanoscale Sensors

This NIRT (nanoscale interdisciplinary research team) project resulted from a proposal submitted in response to the solicitation 'Nanoscale Science and Engineering' (NSF 02-148). The project pursues the growth and study of highly pure, defect-free elemental and compound semiconductor nanowires (SNWs) with diameters as small as 2nm. Fundamental knowledge of the growth and nanofrabication of SNW devices and sensors, as well as the development of generalized nano-workbenches to study electronic and thermal transport in nanowires is sought. The approach to nanowire growth includes 'Electric Field Oriented growth from Nanoscale Tips (EFONT)'. Nano-etching and -doping using a focused ion beam (FIB) will be explored. The project aims to acquire the fundamental knowledge and techniques needed to make state-of-the-art electronic devices and sensors. In the 2-10 nm wire-diameter regime, strong quantum confinement effects in electronic and phonon states are anticipated, but are yet to be studied in detail and theoretically modeled. Raman scattering and photoconductivity measurements will be carried out on individual wires to investigate confinement effects on the electronic and phonon states. Fundamental studies of electrical, optical, phonon and thermal transport properties in nanowires as a function of temperature and doping will be conducted. Detailed, 'on-chip' studies of the transport of heat and charge in isolated small-diameter SNWs will be facilitated by 'nano-workbenches' developed as part of this project. Similarly, SNWs will be investigated as photo-detectors, fast bolometric infrared detectors, gas sensors, high-performance thermoelectric materials, heat sensors, and as heat pipes. A challenging goal of this project is the demonstration of room temperature, single-electron devices from crossed SNWs. SNW n-p junctions and heterojunctions and their electrical and electro-optical properties will also be addressed. The project expects to establish requirements for observation of strong quantum confinement effects in nanowires, and to reduce the size limits of device fabrication with these filaments.

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The project addresses basic research issues in a topical area of materials science and engineering with high technological relevance. An important feature of the program is the integration of research and education through the training of graduate and undergraduate students in a fundamentally and technologically significant area. The project also fosters mentoring between undergraduate students and young people of Pennsylvania communities. A program is in place whereby university faculty, researchers, graduate students and undergraduates participate in hands-on teaching, science-based labs and activities to 5th-8th grade students. This activity is based on weeklong sessions (camps) in several basic science topical areas. A special unit on 'Quantum Wires and Sensors' will be constructed and taught for this summer camp. Undergrads in science and engineering will be employed as camp mentors and also receive a summer research internship with co-PIs. The project is co-supported by the MPS/DMR/EM ENG/ECS/EPDT, ENG/BES, ENG/CTS/TTTP, and MPS/DMR/SSC Divisions/Programs.

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