Technical: This CAREER project addresses a key materials science challenge of the nanoscale science and engineering: developing ability for precise control of nanomaterials structure, size and uniformity and their dopant distribution on the atomic level in order to achieve desired functionality. The research goals are to understand materials science that governs synthesis and doping of semiconductor nanowires and to explore their properties for nanoscale electronics and photonics. The project is comprised of the following interrelated sub-topics: (1) Growth of semiconductor nanowires and nanowire heterostructures with desired structural, optical, magnetic, and electronic properties. New growth facilities will be developed at MIT in order to rationally synthesize semiconductor nanowires and nanowire heterostructures in a controllable fashion. (2) Development of advanced electron microscopy techniques for direct correlation of structural and physical properties at a high spatial resolution. Heterostructure interfaces and dopant distribution will be studied, for example, using aberration corrected Z-contrast scanning transmission electron microscopy. (3) Development of devices such as nanowire-based electrical-injection single photon sources, lasers, and high-electron mobility transistors.
The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to provide new scientific understanding of the nanoworld and potentially contribute to the extension of the information technology revolution. The research component of the project is closely integrated with the educational component. The PI plans to develop a new course "Imaging of Materials" and to create three new laboratory modules for the class "Materials Laboratory" at MIT. She will design and create research and educational internship opportunities for students and high-school teachers, and organize a series of outreach seminars "Nanotechnology for Beginners." It is also planned that materials created through the education/outreach activities will be posted on an interactive Wiki-based web page.
Free-standing nanomaterials – including two dimensional (2D) ultrathin films, one dimensional (1D) nanowires/nanotubes, and zero dimensional (0D) nanocrystals – have properties that are distinct from their bulk counterparts, mostly due to quantum confinement effects and large surface-to-volume ratios. A variety of naturally occurring nanostructured materials can be found in nature giving rise to some unique functionalities. Nanomaterials have also been used through human history, alas, only empirically. The overall goal of this CAREER project is to address some of the key materials challenges of the nanoscale science and engineering; namely, the precise control of material structural properties, size, uniformity, and dopant distribution on the atomic level. As a result of the CAREER project, we have revealed several important insights into the fundamental nanowire growth and doping mechanisms in several compound materials systems, and more recently, we have used this knowledge to control composition and morphology of nanowires in-situ during the growth ("nanowires on demand"). These findings were enabled by the development of a unique growth system in our laboratory, as well as by direct structure-property correlation using state of the art electron microscopy techniques, some of which we have developed. Experimental techniques and methodologies developed as a part of this program have also been a basis of several collaborative projects focusing on structure-property correlation on the nanoscale. Finally, the materials and knowledge developed in this project have been a starting point for the development of devices for applications in nanophotonics, nanoelectronics, and in energy harvesting and conversion.
