1. Picosecond needs for phonon dynamics in nanoscience / energy science Yuelin Li, X-ray Science Division, Argonne National Laboratory

2. 2 Thermoelectricity and energy future 90% of US power is from heat engines with efficiency at 30-40%, thus about 15 TW of heat is lost to the environment Thermoelectric devices can potential convert part of these into electricity. At 1% level, this is equivalent to the total power of 100 1 GW nuclear power plants. Solar thermoelectricity However: efficiency/economics are the key Figure of merit ZT=S 2  T/k K: heat conductivity

3. 3 Thermal electricity and nanoscience: Engineering in thermal electric systems Nanoscience research for energy needs: Report of the national naothechnology initiative grad challenge workshop, http://www.sc.doe.gov/BES/reports/files/NREN_rpt.pdf Link the function and structure at nanoscale Use nanostructure to manipulate energy carrier –Allow electrons to flow, block phonons Figure of merit ZT=S 2  T/k

4. 4 Phonon = Lattice vibration Lattice vibration of nanoparticles: optical methods –Oscillation period T: D (particle size)/ v (sound velocity) For gold nano particles, eg., D=10 nm gives T=3 ps (v=3240 m/s ) Perner et al., ‘,’PRL 85, 792 (2000). Vn Dijk et al., PRL 95, 267406 (2005). Jerebtsov et al., PRB 76, 184301 (2007). Courty, et al., Vibrational coherence of self-organized silver nanocrystals in f.c.c. supra-crystals. Nature Mater. 4, 395–398 (2005). Vibration of nano super lattice –Layer structure, ps time scale Trigo et al., ‘Probing Unfolded Acoustic Phonons with X-rays’, PRL. 101, 025505 (2008) Bargheet et al., ‘Coherent Atomic Motions in a Nanostructure Studied by Femtosecond X-ray Diffraction,’ Science 306, 1771 (2004). Bottom up Acoustic oscillation in a nanoparticles/structures Self organized silver nanoparticle and vibration GaAs/AlGaAs superlattice

5. 5 Bottom upapproach Coupling of phonon oscillation between particle via plasmon oscillation: SPR/lattice vibration is dependent on the particle separation Huang, et al., ‘The Effect of Plasmon Field on the Coherent Lattice Phonon Oscillation in Electron-Beam Fabricated Gold Nanoparticle Pairs,’ Nano Letters 2007 7 (10), 3227-3234

6. 6 Top-down approach Materials with promising Macroscopic-property (heat conductivity) Nano scale structures for low thermal conductivity (0.05 W m -1 K -1 ), and ZT~2.4 –Chiritescu et al., Ultralow Thermal Conductivity in Disordered, Layered WSe 2 Crystals, SCIENCE 315, 351 (2007) –Hochbaum et al., ‘Enhanced thermoelectric performance of rough silicon nanowires’, Nature 451, 163 (2008) –Boukai et al., ‘Silicon nanowires as efficient thermoelectric materials,’ Nature 451, 168 (2008) –A. Majumdar, Thermoelectricity in semiconductor nanostructures, Science 303,777 (2004). –Venkatasubramanian, et al., Thin-film thermoelectric devices with high roomtemperature figures of merit, Nature 413, 597 (2001). –Harmon et al., Quantum dot superlattice thermoelectric materials and devices, Science 297, 2229 (2002). Challenges –Phonon dynamics unknown –Very challenging to model (for all nano sctructures!) Disordered WSe 2 layers Silicon naowires

7. 7 Time resolved x-ray measurement: Bridge the macro to nano scales: phonon/propagation Heat = Phonon = Lattice vibration –Excite phonons: Laser pump –See phonons and propagation: x-ray probe with XRD, GISAX, …… Requires ps resolution –Ultrafast lasers: Yes –ps x-ray pulses: No  –ps detector: Y&N (streak camera at Sector. 7)  –Theory and simulation We already have other resources: –CNM, MSD, APS, U-Chicago, North-Western, and other With the ps x-ray source, we can –better understand nanostructure for all purposes –design better thermoelectric material for future sustainable energy source –help others time resolved activities

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9. 9 Taking LCLS into account APS Short pulse/detector vs. LCLS –Pro: Existing infrastructure and collaboration Stability, availability Higher average photon flux Better sample survivability –Con Low peak photon flux Mentally less dazzling LCLS pro and con –Pro Shorter pulse with high photon flux Mentally more dashing –Con Availability and beam time allocation Sample survivability unwilling travel for users