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Title: The dynamics of femtosecond pulsed laser removal of 20 nm Ni films from an interface

The dynamics of femtosecond laser removal of 20 nm Ni films on glass substrates was studied using time-resolved pump-probe microscopy. 20 nm thin films exhibit removal at two distinct threshold fluences, removal of the top 7 nm of Ni above 0.14 J/cm{sup 2}, and removal of the entire 20 nm film above 0.36 J/cm{sup 2}. Previous work shows the top 7 nm is removed through liquid spallation, after irradiation the Ni melts and rapidly expands leading to tensile stress and cavitation within the Ni film. This work shows that above 0.36 J/cm{sup 2} the 20 nm film is removed in two distinct layers, 7 nm and 13 nm thick. The top 7 nm layer reaches a speed 500% faster than the bottom 13 nm layer at the same absorbed fluence, 500–2000 m/s and 300–700 m/s in the fluence ranges studied. Significantly different velocities for the top 7 nm layer and bottom 13 nm layer indicate removal from an interface occurs by a different physical mechanism. The method of measuring film displacement from the development of Newton's rings was refined so it could be shown that the 13 nm layer separates from the substrate within 70 ps and accelerates to its final velocity within several hundred picoseconds. We propose that removal of the bottom 13 nm is consistent with heterogeneousmore » nucleation and growth of vapor at the Ni-glass interface, but that the rapid separation and acceleration of the 13 nm layer from the Ni-glass interface requires consideration of exotic phases of Ni after excitation.« less
Authors:
;  [1] ;  [2]
  1. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)
  2. Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States)
Publication Date:
OSTI Identifier:
22482153
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; EXCITATION; GLASS; INTERFACES; IRRADIATION; LASERS; LAYERS; MICROSCOPY; SUBSTRATES; THIN FILMS; TIME RESOLUTION; VAPORS