Professor
Orr’s research centers on systems where the properties
are controlled by the characteristics of surfaces or interfaces.
As designed structures become ever smaller, their surface characteristics
begin to influence, or even control, their behavior. Often the
research involves scanning probe microscopies such as STM and
AFM. Specific examples of research interests include: studies
of molecules adsorbed on Si and Au surfaces, the molecular origin
of negative differential resistance in metal-insulator-metal
devices, the mechanism for composition modulation in compound
semiconductors grown by molecular-beam epitaxy and the development
of multifunctional nanoparticles as therapeutics for cancer
treatment.
The
demand for smaller, faster silicon-based MOSFET’s necessitates
the creation of thinner, more stable insulating silicon oxide
(SiO2) layers. To achieve this a detailed understanding of the
oxidation process and the structure of the Si/SiO2 is key. Our
research has involved examining a model of this interface and
determining the structure with atomic resolution. The theme
of atomically resolved surface structure continues in my research
on the MBE growth of compound semiconductors and the spontaneous
creation of compositionally modulated superlattices. We are
also examining novel molecules that bind to gold and form self-assembled
monolayers.
A
second part of my research is the creation of targeted drugs
for chemotherapy. This work involves the study of functionalized
poly(amidoamine) dendrimers as drug transport agents. We are
studying the interaction of these nanoparticles with lipid layers,
cell membranes and cells. In situ AFM is has been used to examine
cell apoptosis (programmed cell death) that occurs as a result
of successfully killing the cancer cell.
Most
of the research being performed is interdisciplinary and falls
in the broad category of nanotechnology. I have active collaborations
with researchers in the departments of Chemistry and Material
Science as well the Medical School and the Center
for Biologic Nanotechnology. By combining our respective
areas of expertise we are able to address problems from a number
of angles. This has proven to be a very successful and powerful
style of research for my group.
