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Title: Generating gradient germanium nanostructures by shock-induced amorphization and crystallization

Gradient nanostructures are attracting considerable interest due to their potential to obtain superior structural and functional properties of materials. Applying powerful laser-driven shocks (stresses of up to one-third million atmospheres, or 33 gigapascals) to germanium, we report a complex gradient nanostructure consisting of, near the surface, nanocrystals with high density of nanotwins. Beyond there, the structure exhibits arrays of amorphous bands which are preceded by planar defects such as stacking faults generated by partial dislocations. At a lower shock stress, the surface region of the recovered target is completely amorphous. Here, we propose that germanium undergoes amorphization above a threshold stress and that the deformation-generated heat leads to nanocrystallization. These experiments are corroborated by molecular dynamics simulations which show that supersonic partial dislocation bursts play a role in triggering the crystalline-to-amorphous transition.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [1] ; ORCiD logo [4] ;  [5]
  1. Univ. of California, San Diego, CA (United States). Materials Science and Engineering Program
  2. Univ. of California, San Diego, CA (United States). Dept. of Structural Engineering
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Univ. of California, San Diego, CA (United States). Materials Science and Engineering Program; Univ. of California, San Diego, CA (United States). Dept. of Mechanical and Aerospace Engineering; Univ. of California, San Diego, CA (United States). Dept. of Nanoengineering
Publication Date:
Grant/Contract Number:
AC05-00OR22725; NA0002930; AC52-07NA27344
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 37; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; amorphization; laser shock; nanocrystallization; germanium; gradient materials
OSTI Identifier:
1377093
Alternate Identifier(s):
OSTI ID: 1414697