Abstract
We monitored the femtosecond-laser-induced lattice dynamics in PbSe quantum dots by ultrafast electron diffraction. The electron-phonon coupling didn’t show phonon bottleneck. And lattice dilation exhibited unusual features. Heat transport to the substrate deviated significantly from Fourier’s Law.
Highlights
Lead selenide (PbSe) quantum dots (QD) are photoactive in the near infrared region with very high photoluminescence quantum yields
We demonstrated a method of probing the electron-phonon coupling in QDs through directly monitoring the lattice system with ultrafast electron diffraction (UED)
The lattice temperature rose in about 10 ps and fell back to the original value in about 40 ps; while the lattice spacing showed an initial 6 ps rise faster than lattice temperature, and didn’t return back to the original value
Summary
Lead selenide (PbSe) quantum dots (QD) are photoactive in the near infrared region with very high photoluminescence quantum yields. Electron and hole Bohr radii in PbSe QDs are so large (about 23 nm) that both carriers experience very strong confinement in sub-10 nm particles [1]. We demonstrated a method of probing the electron-phonon coupling in QDs through directly monitoring the lattice system with ultrafast electron diffraction (UED). We traced the lattice temperature, its dilation, and the heat transport from QDs to the substrate.
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