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SUMMARY:Time-Resolved Probes of Lattice Dynamics in Technologically Releva
 nt Semiconductors
DTSTART:20190523T171500
DTEND:20190523T181500
DTSTAMP:20260406T170504Z
UID:39d6fd6b2b1479005af4f8bab1617f5df33495290bd07ea495361b2d
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Richard Schaller\nNorthwestern University\nThe role of t
 hermal energy deposition in nanoparticles and bulk semiconductors with nan
 oscopic features has not been substantively probed\, yet can impact materi
 al function. I will present studies of ultrafast optical-pump\, x-ray diff
 raction probe as well as infrared-pump electronic-probe performed on semic
 onductor nanocrystal (NC) colloidal dispersions as functions of particle s
 ize\, polytype\, and pump intensity to examine lattice response in materia
 ls such as CdSe and lead halide perovskites. In x-ray experiments\, shifts
  of Bragg peaks relate lattice heating and peak amplitude reduction convey
 s transient lattice disordering (or melting). Intraband and Auger-derived 
 heating is clearly observed for low fluences\, and disordering was observe
 d upon absorption of larger numbers of photons excitations per NC on avera
 ge. Perovskites are shown to undergo solid-solid phase transitions followe
 d by melting at elevated fluences. Infrared-pump experiments offer insight
 s into thermal dissipation within these compositions including sub-lattice
  coupling and interfacial thermal conductance. These findings suggest a ne
 ed to take into account nanomaterial physical stability and transient elec
 tronic structure for high intensity excitation applications such as lasing
  and solid-state lighting.
LOCATION:BCH 2201 https://plan.epfl.ch/?room==BCH%202201
STATUS:CONFIRMED
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