Advisor: Paul R. Berger
Phillip E. Thompson (Naval Research Laboratory)
Ilesanmi Adesida (University of Illinois at Urbana-Champaign)
Patrick J. Fay (University of Notre Dame)
Gregory L. Snider (University of Notre Dame)
Alexei O. Orlov (University of Notre Dame)
Roger Lake (University of California at Riverside)
Former Graduate Students:
Ms. Anisha Ramesh (ECE Ph.D. 2012)
Si-Young Park (Master's Thesis 2006, Ph.D. 2009)
Ronghua Yu (Physics Ph.D. 2007)
Sung-Yong Chung (Master's Thesis 2002, Ph.D. 2005)
Sandro Di Giacomo (Master's Thesis 2005)
Niu Jin (Ph.D. 2004)
Matter as we encounter it in our daily lives takes on certain bulk properties with which we have become familiar. Mankind has probed the boundary edges of these materials over the centuries by purifying and mixing elements to form new materials and alloys with slightly enhanced properties. However, with the advent of modern processing techniques, materials can be reduced in size to the nanoscale with high yield and repeatability. At first, precision deposition techniques permitted the control of the layering dimensions vertically, shrinking to lengthscales that effectively confines an electron wave function in 1-dimension. The material is then considered to be confined to a reduced dimensionality. If confinement is in two orthogonal directions, then quantum wires can be synthesized, and if all three dimensions confined, a quantum dot is fashioned. Quantum dots are perhaps the easiest of these to realize in the form of nanoparticles or self-assembled islands. To a large degree, paints and other colorants over the centuries have exploited these properties unknowingly.
Now at these nanoscale dimensions, the behavior and material properties of this nanostructured material can be altered tremendously from their known bulk values. For instance, the traditional and ubiquitous semiconductor, silicon, can perform many functions in modern-day electronics, except emit light efficiently. Silicon is an indirect bandgap material. However, at the nanoscale, not only does the bandgap of a silicon nanoparticle become significantly larger than its bulk value, but it is predicted that it may also become a direct bandgap material, significantly altering its underlying band structure and possibly permitting light to be squeezed out of silicon efficiently.
Continued scaling of CMOS transistors is expected to reach diminishing returns in the years to come.
More more background information, see:
Si-based nanowires with high aspect ratios have been fabricated using inductively-coupled plasma reactive ion etching (ICP-RIE) with a continuous processing gas mixture of fluorine based SF6:C4F8 combined with a thermal oxidation technique. The subsequent thermal oxidation further reduced the nanowire diameter utilizing the self-limiting oxidation effect below the lithographic dimensions. TEM analysis of the completed nanostructures revealed the total oxide thickness and the consumption of the Si core which determines the inner nanowire diameter. The final dimensions of the inner Si nanowire are about 600 nm tall and less than 25 nm wide using top-down processing techniques.
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