Research Areas:
Selective growth of Ge quantum structures/high-quality heteroepitaxial films on Si; atom-tracking scanning tunneling microscopy to fundamentally understand the selective growth process; hybrid micro/nanofluidic systems for advanced bioseparation and analysis; synthetic modification of semiconductor surfaces for the purpose of probing functional activities of biomolecules; and high-yield Ge0 nanocrystal (NC) synthesis from novel Ge(II) precursors and NC surface functionalization.

Brief Description of Research:
I envision a nationally reputable research program in Micro to Atomic Scale Interfacial Science and Engineering on Si and Ge Based Systems. The above figure presents an overview of my research program where the fabrication technology forms the centerpiece and lends itself to (1) defining nanoscale features in thin films, (2) creating templates to grow coherent quantum structures and epitaxial films, (3) creating nanofluidic channels for advanced separation and detection of biomolecules, and (4) providing a platform for surface functionalization to study biomolecular interactions with synthetically created surfaces. Our strategy is to fundamentally understand the interfacial phenomena at multiple length scales and to utilize that understanding to solve engineering problems, such as growing high-quality lattice mismatched materials on Si and separating biomolecules in nanofluidic channels. I provide below a few select research topics that provide a framework for my research program.

High-quality Ge Epitaxy on Si by Nanoscale Heterojunction Engineering - A Foundation for III-V and II-VI Integration†: Our research objective is to develop a comprehensive materials engineering solution to integrate high-quality III-V and II-VI heteroepitaxial films on Si, utilizing (1) properly sized Ge seeds (3 to 100 nm in width) and (2) their fully coalesced film as an interlayer. To grow high-quality Ge on Si, we manipulate the growth surface at the nanoscale to significantly reduce the strain at the heterojunction. Our general engineering approach is to insert a thin, perforated dielectric layer (2 to 12 nm wide openings and 1 to 10 nm in thickness) between Ge and Si. This technique, as an alterative to metamorphic growth and wafer bonding/cutting, is uniquely different from the epitaxial lateral overgrowth in that the characteristic dimension of the Ge-Si heterojunction ensures coherent Ge seed pads and that the remaining interlayer serves as artificially introduced dislocations that relieve the strain.
Fundamental Understanding of Ge Adspecies Transport on SiGe Wetting Layer and Partially Oxidized Si Using Scanning Tunneling Microscopy - A Path to Selective Growth: To complement the above materials engineering effort and to understand at the atomic-level the selective growth of Ge on Si, rather than on a dielectric layer (e.g., SiO2), we have employed scanning tunneling microscopy. We have so far identified adatom pairs (or c-dimers), shown in the STM image of Fig. 1, as the main transport species on SiGe 2xN surfaces. The main scientific goal is to determine the surface mechanism responsible for the selectivity.
Hybrid Micro/Nanofluidics for Advanced Separation and Anaysis of Biomolecules‡: This research focuses on how the unique characteristics of nanochannels influence the structure and orientation of protein molecules as well as their biofunctional activities. We intend to explicitly measure the effects of nanochannel geometry, double layer overlap, pH modulation, "gate" potential for the field effect transistor (FET) analogue, and externally applied electric field for electrophoresis. Our scientific goal is to render an accurate description of biomolecular structural changes, reaction, and transport in nanochannels as a function of built-in as well as externally applied potentials.
Summary
The objective of my research program is to carve out a unique contribution to electronic materials research as well as bioseparations, and to help my University to capture national prominence in engineering education. My commitment to the research-oriented science and engineering education is demonstrated by the immediate dissemination of research results through specialized graduate-level courses, the inclusion of undergraduates in my research program, the recruitment of underrepresented students, and the individualized approach to teaching.

† UNM-650 US Patent application was filed on September 8, 2004.
‡ UNM-675 US Patent application was filed on July 19, 2004.

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