Material Science

Prof. Tanenbaum’s PhD at the University of Colorado and the National Renewable Energy Laboratory was focused on UHV STM measurements of amorphous silicon thin films used in thin film photovoltaic cells to understand the evolution of structural voids during the film growth. A parallel project focused on using the STM for nanolithography, became a recurring theme in later work. Postdoctoral research at Cornell University developing both field emitters and novel lithographic processing for low energy electron beam lithography continues to be an active area of research.

Prof. Tanenbaum and his students have been regular users of the Cornell nanofabrication and characterization facilities for many years, even as our group’s research evolved from lithography to nano-mechanical resonators, microfluidics, carbon nanotubes, graphene, and eventually back to photovoltaics. Pomona undergraduates have worked in all these areas. Prof. Tanenbaum recently spent a one-year sabbatical leave in Denmark at working with Dr. Frederik Krebs to apply nanotube networks and graphene films as replacements for Indium Tin Oxide (ITO) as the transparent conductor in low cost organic photovoltaics (OPVs). ITO is the most expensive part of OPVs today, and its brittle nature is not a good match for flexible cells. Carbon nanotubes and graphene sheets have the potential to both lower the cost and increase the reliability. Our research group continues to explore approaches to enhance the stability of OPVs by employing new materials and device structures.

There is a tendency to describe academic research as narrow and deep, to the point where it may no longer have much relevance. Our group strives to be important and vibrant, evolving with major trends in science. Recently the Nobel Prize in physics was awarded for research on graphene, and Pomona students have been working on projects connected with graphene in our labs for the past six years.

While extended research collaborations with Cornell University and newer international collaborations on OPVs are very important to our research, we focus on research projects that can be accomplished at Pomona College. Our research labs and facilities at Pomona support undergraduate research students year-round in current research fields. Student researchers have unlimited access to wet chemistry, spin coating, thermal evaporation, micro-contact printing, UV ozone cleaning, oxygen plasma cleaning, sputter coating, critical point drying, optical microscopy, optical lithography, ellipsometry, thin film spectral reflectivity, Raman spectroscopy, current-voltage characterization, simulated solar sources, outdoor solar tracking, chemical vapor deposition for growth of single-walled nanotubes and graphene, atomic force microscopy, scanning tunneling microscopy, field emission electron microscopy, electron beam lithography, and energy dispersive x-ray spectroscopy.

Currently the focus in our lab is on fabrication, characterization, and stability of OPV devices, and the creation, application, and properties of novel materials such as carbon fullerenes and nanotubes, graphene, semiconducting polymers, and quantum dot materials. In Fall of 2012 we installed a new state of the art electron microscopy facility which is arguably the best electron microscopy facility dedicated to undergraduate research in the world.