Micro/nanostructures formation by femtosecond laser surface processing on amorphous and polycrystalline Ni60Nb40

Authors

Edwin Peng, University of Nebraska-LincolnFollow
Alfred Tsubaki, University of Nebraska-LincolnFollow
Craig A. Zuhlke, University of Nebraska-LincolnFollow
Meiyu Wang, University of Nebraska-Lincoln
Ryan Bell, University of Nebraska-Lincoln
Michael J. Lucis, University of Nebraska-Lincoln
Troy P. Anderson, University of Nebraska-LincolnFollow
Dennis R. Alexander, University of Nebraska-LincolnFollow
George Gogos, University of Nebraska-LincolnFollow
Jeffrey E. Shield, University of Nebraska-LincolnFollow

Date of this Version

2017

Citation

Appl Surf Sci. 2017 February 28; 396: 1170–1176.

Comments

Copyright 2016 Elsevier B.V.

Abstract

Femtosecond laser surface processing is a technology that can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophilicity/superhydrophobicity. In this study, two unique classes of surface structures, below surface growth (BSG) and above surface growth (ASG) mounds, were formed by femtosecond laser surface processing on amorphous and polycrystalline Ni₆₀Nb₄₀ with two different grain sizes. Cross sectional imaging of these mounds revealed thermal evidence of the unique formation processes for each class of surface structure. BSG mounds formed on all three substrates using the same laser parameters had similar surface morphology. The microstructures in the mounds were unaltered compared with the substrate before laser processing, suggesting their formation was dominated by preferential valley ablation. ASG mounds had similar morphology when formed on the polycrystalline Ni₆₀Nb₄₀ substrates with 100 nm and 2 [H9262]m grain size. However, the ASG mounds had significantly wider diameter and higher peak-to-valley heights when the substrate was amorphous Ni₆₀Nb₄₀. Hydrodynamic melting was primarily responsible for ASG mound formation. On amorphous Ni₆₀Nb₄₀ substrates, the ASG mounds are most likely larger due to lower thermal diffusivity. There was clear difference in growth mechanism of femtosecond laser processed BSG and ASG mounds, and grain size does not appear to be a factor.