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Title: In situ dynamic TEM characterization of unsteady crystallization during laser processing of amorphous germanium

The unsteady propagation mechanism for the crystallization of amorphous germanium (a-Ge) was studied with in situ movie-mode dynamic transmission electron microscopy (MM-DTEM). We used short laser pulses to heat sputter-deposited a-Ge films and the resulting crystallization process was imaged with up to 16 sequential 50 ns long electron pulses separated by a controlled delay that was varied between 0.5 and 5 μs. The unsteady crystallization in the radial, net-growth direction was observed to occur at a decreasing rate of ~1.5–0.2 m/s through a mechanism involving the formation of discrete ~1.1 μm wide bands that grew with velocities of 9–12 m/s perpendicular to the radial direction and along the perimeter of the crystallized area. The crystallization rate and resulting microstructure were consistent with a liquid-mediated growth mechanism, which suggests that locally the band front reaches the amorphous melting temperature of Ge. Furthermore, a mechanism based on the notion of a critical temperature is proposed to explain the unsteady, banded behavior.
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-733656
Journal ID: ISSN 1359-6454; TRN: US1800938
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 143; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1416492

Egan, Garth C., Li, Tian T., Roehling, John D., McKeown, Joseph T., and Campbell, Geoffrey H.. In situ dynamic TEM characterization of unsteady crystallization during laser processing of amorphous germanium. United States: N. p., Web. doi:10.1016/j.actamat.2017.10.003.
Egan, Garth C., Li, Tian T., Roehling, John D., McKeown, Joseph T., & Campbell, Geoffrey H.. In situ dynamic TEM characterization of unsteady crystallization during laser processing of amorphous germanium. United States. doi:10.1016/j.actamat.2017.10.003.
Egan, Garth C., Li, Tian T., Roehling, John D., McKeown, Joseph T., and Campbell, Geoffrey H.. 2017. "In situ dynamic TEM characterization of unsteady crystallization during laser processing of amorphous germanium". United States. doi:10.1016/j.actamat.2017.10.003. https://www.osti.gov/servlets/purl/1416492.
@article{osti_1416492,
title = {In situ dynamic TEM characterization of unsteady crystallization during laser processing of amorphous germanium},
author = {Egan, Garth C. and Li, Tian T. and Roehling, John D. and McKeown, Joseph T. and Campbell, Geoffrey H.},
abstractNote = {The unsteady propagation mechanism for the crystallization of amorphous germanium (a-Ge) was studied with in situ movie-mode dynamic transmission electron microscopy (MM-DTEM). We used short laser pulses to heat sputter-deposited a-Ge films and the resulting crystallization process was imaged with up to 16 sequential 50 ns long electron pulses separated by a controlled delay that was varied between 0.5 and 5 μs. The unsteady crystallization in the radial, net-growth direction was observed to occur at a decreasing rate of ~1.5–0.2 m/s through a mechanism involving the formation of discrete ~1.1 μm wide bands that grew with velocities of 9–12 m/s perpendicular to the radial direction and along the perimeter of the crystallized area. The crystallization rate and resulting microstructure were consistent with a liquid-mediated growth mechanism, which suggests that locally the band front reaches the amorphous melting temperature of Ge. Furthermore, a mechanism based on the notion of a critical temperature is proposed to explain the unsteady, banded behavior.},
doi = {10.1016/j.actamat.2017.10.003},
journal = {Acta Materialia},
number = C,
volume = 143,
place = {United States},
year = {2017},
month = {10}
}