@article{adb9347cf9c24e2db4999d20d47a53b8,
title = "Transient Melting and Recrystallization of Semiconductor Nanocrystals under Multiple Electron-Hole Pair Excitation",
abstract = "Ultrafast optical pump, X-ray diffraction probe experiments were performed on CdSe nanocrystal (NC) colloidal dispersions as functions of particle size, polytype, and pump fluence. Bragg peak shifts related to heating and peak amplitude reduction associated with lattice disordering are observed. For smaller NCs, melting initiates upon absorption of as few as ∼15 electron-hole pair excitations per NC on average (0.89 excitations/nm3 for a 1.5 nm radius) with roughly the same excitation density inducing melting for all examined NCs. Diffraction intensity recovery kinetics, attributable to recrystallization, occur over hundreds of picoseconds with slower recoveries for larger particles. Zincblende and wurtzite NCs revert to initial structures following intense photoexcitation suggesting melting occurs primarily at the surface, as supported by simulations. Electronic structure calculations relate significant band gap narrowing with decreased crystallinity. These findings reflect the need to consider the physical stability of nanomaterials and related electronic impacts in high intensity excitation applications such as lasing and solid-state lighting.",
keywords = "Nanocrystals, melting, molecular dynamics, multiexciton, phonon, transient diffraction",
author = "Kirschner, {Matthew S.} and Hannah, {Daniel C.} and Diroll, {Benjamin T.} and Xiaoyi Zhang and Wagner, {Michael J.} and Dugan Hayes and Chang, {Angela Y.} and Rowland, {Clare E.} and Lethiec, {Clotilde M.} and Schatz, {George C.} and Chen, {Lin X.} and Schaller, {Richard D.}",
note = "Funding Information: *E-mail: schaller@anl.gov; schaller@northwestern.edu. ORCID Benjamin T. Diroll: 0000-0003-3488-0213 George C. Schatz: 0000-0001-5837-4740 Richard D. Schaller: 0000-0001-9696-8830 Author Contributions M.S.K., D.C.H., B.T.D., X.Z., M.J.W., D.H., A.C.C., C.E.R., C.M.L, L.X.C., and R.D.S. performed the TR-XRD experiments and analyzed the data. B.T.D. performed the nanoparticle synthesis. D.C.H., C.M.L., and G.C.S. performed theoretical modeling and calculations. All authors contributed to the writing of this paper. M.S.K. and D.C.H. contributed equally to this work. Funding We acknowledge support from the Ultrafast Initiative of the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, through Argonne National Laboratory under Contract No. DE-AC02-06CH11357. D.K.H. is supported by the Joseph J. Katz Postdoctoral Fellowship at ANL. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Notes The authors declare no competing financial interest. Funding Information: We acknowledge support from the Ultrafast Initiative of the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, through Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.",
year = "2017",
month = sep,
day = "13",
doi = "10.1021/acs.nanolett.7b01705",
language = "English",
volume = "17",
pages = "5315--5320",
journal = "Nano Letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "9",
}