Research Interests: synthesis, modeling, and development of nanoscale materials and devices for new electronic, photonic, and energy applications
Key to these technological developments is morphological control during synthesis and understanding the finite-size effects that manifest at the nanoscale for cutting edge modern technologies (such as transistors, memory, etc.). Characterization of these new materials and morphologies (shapes and structures) is essential, as they often break the rules that we expect as classical physics gives way to quantum mechanics at the nanoscale.
Three classic problems often occur in nanoscience research. At the nanoscale, atomic-scale effects like quantum mechanics, bonding, etc. dominate in ways we often ignore in our everyday lives. These effects are generally understood via simple models, but the field of nanoscience is unsure how all these effects work together in the real world, limiting our ability to fabricate at the nanoscale by anything other than trial and error. The second major problem is scaling. The world is using more nanoscale materials than ever before and this need will continue to grow in the future. Fundamental research is needed to determine the best material choices, the best types of structures, etc. for industries to develop technologies with as little waste as possible. The third major issue is assembly. Manipulating and building samples on the nanoscale is very challenging and current tools are time-intensive and wasteful. Further understanding regarding how to assemble and grow nanostructures is paramount for society to build future nanotechnology with the speed, precision, efficiency, reliability, and tailored properties demanded.
The experiments performed in Chris’ lab first start with sample growth. This is done in a home-built chemical vapor deposition reactor capable of transporting gases to a deposition chamber where we essentially “cook” with the various elements of the periodic table. The furnaces (maximum temperature 1500°C), gas pressures, valves, gas flow rates, etc. are all computer controlled to maintain consistent growth recipes and programmed via LabVIEW. Basic characterization occurs at Lafayette with a metallurgical microscope in-lab and scanning electron microscopy in a shared science and engineering facility. Typical nanowire, film, and nanoparticle samples of various materials are on the order of tens of nanometers in size.
More advanced characterization is often needed for new types of samples, as large scale behaviors rarely transfer directly to the nanoscale. More advanced optical characterization techniques in Chris’ lab include high resolution Raman spectroscopy and photoluminescence measurements. These are performed with visible and UV lasers using a free-space optics setup and a high resolution spectrometer. Additionally, samples are mounted on a stage with tens of nanometer resolution and the ability to heat the sample from liquid nitrogen temperatures (-196°C) up to 600°C. This variable temperature spectroscopy is especially useful in characterizing the structure and properties of new materials with unknown properties.
Ethan Garvey ’19 worked in Chris’ lab for his senior thesis building optical setups and characterizing ferroelectric materials via Raman spectroscopy.