Interfacial Thermal Transport
    Interfaces play a critical role in thermal transport, especially at low temperatures and in nanostructured materials. We are interested in interfacial thermal transport and phonon scattering at grain boundaries, surfaces, and heterointerfaces. Key to understanding structure-property relationships is a detailed understanding of fundamental scattering mechanisms.
   To elucidate the underlying mechanisms of interfacial conductance, we have developed wave-packet simulation techniques as a complement to standard molecular-dynamics simulations. The basic idea is to create a phonon wave packet that propagates in a molecular-dynamics simulation and scatters from defects and interfaces. By analyzing the final state of the system, detailed phonon couplings are revealed.
       Below is a simulation movie that demonstrates the technique. A wave packet corresponding to a longitudinal acoustic mode with a wavelength of about 3 lattice parameters is scattered from a high-energy twist grain boundary in silicon. The entire system has about 100,000 atoms, and the total simulation time is approximately 30ps.

gbmovie

Scientific Highlights:
Key collaborators:

Pawel Keblinski and Arun Bodapati, Rennselaer Polytechnic Institute
Simon Phillpot, University of Florida
Ken Goodson, Stanford University
Sanjiv Sinha, Intel Corporation
Chris Kimmer, University of Louisville
Sylvie Aubry, Ed Piekos, and Ed Webb, Sandia National Laboratory
O. Auciello, J.A. Carlisle, and J.A. Eastman, Materials Science Division, Argonne National Laboratory
Theodorian Borca-Tasuic, Rennselaer Polytechnic Institute
Li Shi, University of Texas-Austin

Students:

Ph.D.
Brian Becker (UCF Physics), Arun Bodapati (RPI Materials Science, graduated July 2006)

Undergraduate
Nushien Shahnami (UCF Physics)

Funding:

Consultant, Sandia National Laboratory, June 2005-present

References:

1. C. Kimmer, S. Aubry, Ashton Skye, and Patrick Schelling, "Scattering of phonons from a high-energy grain boundary in silicon: Dependence on angle of incidence", in preparation for submission to Phys. Rev. B (2006)

2. A. Bodapati, P.K. Schelling, S.R. Phillpot, and P. Keblinski, "Vibrations and transport in nanocrystalline silicon," submitted to Phys. Rev. B (2006)

3. A. Bodapati, P.K. Schelling, and P. Keblinski, "Effect of Point Defects on Phonons in Carbon Nanotubes," submitted to Phys. Rev. Lett. (2006)

4. B. Becker, P.K. Schelling, and S.R. Phillpot, "Interfacial Phonon Scattering in Semiconductor Nanowires by Molecular-Dynamics Simulation," J. Appl. Phys. 99, 123715 (2006)

5. A. Bodapati, P.K. Schelling, S.R. Phillpot, and P. Keblinski, "Crossover in thermal transport mechanism in nanocrystalline silicon," Appl. Phys. Lett. 88, 141908 (2006)

6. M. A. Angadi, T. Watanabe, A. Bodapati, X. Xiao, O. Auciello, J.A. Carlisle, J.A. Eastman, P. Keblinski, P.K. Schelling, and S.R. Phillpot, "Thermal Transport and grain-boundary conductance in ultrananoscrytalline diamond thin films,"  J. Appl. Phys. 99, 114301 (2006)

7. P.K. Schelling, L. Shi, and K.E. Goodson, "Managing Heat for Electronics," Mat. Today 8, 30 (2005)

8. S.R. Phillpot, P.K. Schelling, and P. Keblinski, "Interfacial thermal conductivity: Insights from atomic level simulation," J. Mat. Sci. 40, 3143 (2005) Eleventh Int. Conf. on Intergranular and Interphase Boundaries 2004

9. S. Sinha, P.K. Schelling, S.R. Phillpot, and K.E. Goodson, "Scattering of g-process longitudinal optical phonons at hotspots in silicon," J. Appl. Phys. 94, 023702 (2005)

10. B. Becker, P.K. Schelling, and S.R. Phillpot, "Computational studies of nanoscale phonon transport and interfacial scattering," Phys. Stat. Sol. (c) 1, 2955 (2004)

11. P.K. Schelling, S.R. Phillpot, and P. Keblinski, "Kapitza conductance and phonon scattering at grain boundaries by simulation," J. Appl. Phys. 95, 6082 (2004)

12. P.K. Schelling and S.R. Phillpot, "Multiscale simulation of phonon transport in superlattices," J. Appl. Phys. 93, 5277 (2003)

13. P.K. Schelling, S.R. Phillpot, and P. Keblinski, "Phonon wave-packet dynamics at semiconductor interfaces by molecular-dynamics simulation," Appl. Phys. Lett. 80, 2484 (2002)