Bottom-Up Solutions to Plasma Synthesis of Nanomaterials

Large-scale, low-pressure plasmas are essential to the manufacturing of integrated circuits
that are now ubiquitous in consumer electronics. However, challenges have arisen for these topdown
approaches to materials processing. Future electronic devices will incorporate nanoscale
materials such as nanoparticles, carbon nanotubes, and silicon nanowires that must be prepared
from the “bottom-up” because of the current limitations of photolithography. In addition, emerging
applications in sensors, energy, and medicine require nanomaterials that are not easily fabricated
by current plasma tools. The aim of our research is to develop a new class of plasmas, termed
“microplasmas”, for nanomaterials synthesis. Unlike conventional plasmas used in materials
processing, microplasmas operate at small volumes (less than 1 nanoliter!) and high pressures (up
to and exceeding atmospheric). These unique features open new avenues for material synthesis.
Vapors of metal-organic precursors can be non-thermally dissociated by the “hot” electrons
contained in a microplasma to homogeneously nucleate nanoparticles from gas-phase radicals.
Excessive particle growth and agglomeration are limited by short reactor residence times, leading
to the formation of uniform particles less than 5 nm in size. The synthesis of nanometer-sized
metal particles lends itself to catalytic applications including carbon nanotube and silicon nanowire
growth. Recently, we have also coupled microplasmas with liquids or polymeric films to nucleate
nanoparticles from metal ions. In this talk, I will discuss these topics in detail, highlighting materials
synthesis, characterization, and applications.
Dr. Mohan Sankaran is the George B. Mayer Asst. Professor of Chemical
Engineering at Case Western Reserve University (CWRU). He received his BS in Chemical
Engineering from the University of California at Los Angeles in 1998 and his Ph.D. in Chemical
Engineering from the California Institute of Technology in 2004. At Caltech, he received
fellowships from the National Science Foundation, Intel Foundation, and Applied Materials. In
2000, he was awarded the Constantine G. Economou Prize. He joined the Dept. of Chemical
Engineering at CWRU in 2005 as the John Angus Legacy Asst. Professor. As a faculty member,
he received the NSF CAREER Award, the CWRU Glennan Fellowship, and the Young Investigator
Program Award from AFOSR. His current research interests include microplasmas, nanoparticle
synthesis, carbon nanotube and silicon nanowire growth, surface-enhanced Raman spectroscopy,
plasma electrochemistry, and electrostatic charging of materials.