Nanoscale Heat Transport at Organic-Inorganic Interfaces
*Faculty only 12:00 — 12:30 PM (Non-ME Faculty are welcome)

Mark Losego, Ph.D.  
Assistant Research Professor
Department of Chemical &
Biomolecular Engineering
North Carolina State University

Compared with our ability to precisely control the flow of electrons or light within a material, our capacity to design the flow of heat, particularly at the nano-scale, is rather rudimentary. Crucial to nanoscale thermal  management  is  an  understanding  of  interfacial  heat  transport.  Interfaces  between  two  materials  act  as barriers to heat flow. For nano-scale systems, these interfaces largely determine the thermal conductivity of the entire material. However, thermal transport across interfaces is still not well understood. This talk will describe experimental work that attempts to validate recent molecular dynamics (MD) simulations suggesting  that  interfacial  thermal  conductance  can  be  strongly  modulated  by  adjusting  the  strength  of  
interfacial bonds.  Our experimental system consists of self-assembled monolayers (SAMs) on SiO₂ substrates having either methyl or mercapto terminations.  Gold films are transfer printed onto these surfaces forming  either  a  van  der  Waals  or  covalent  bond  respectively.    The  interfacial  thermal  conductance  across  the  Au/SAM  interface  is  measured  via  time-domain  thermoreflectance  (TDTR)  and  found  to  increase  by  nearly  2x  when  the  interface  is  switched  from  a  van  der  Waals  interaction  to  a  covalent  bond.    The  interfacial  bond  stiffness  is  independently  measured  using  pico-second  acoustics.    Together  these experiments represent the first clear demonstration of how changing the stiffness of a single atomic-scale interfacial bonding layer affects thermal conductance.  Methods for expanding this understanding to  create  new  materials  systems  will  be  discussed  
as  well  as  opportunities  for  engineering  organic-inorganic interfaces for other molecularly enabled systems. 

Mark D. Losego is an Assistant Research Professor of Chemical and Biomolecular Engineering at North Carolina  State  University.    He  earned  his  Ph.D.  in  materials  science  and  engineering  at  North  Carolina  State University in 2008 and conducted postdoctoral research in nano-scale heat transport at the University of Illinois until 2011.  Losego’s research focuses on understanding transport phenomena at organic /inorganic interfaces and within three-dimensionally nanostructured systems used in energy and environmental applications.