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Creation of micro/nano surface structures on silver using collinear double femtosecond laser pulses with different pulse separation

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Self-organized mound-like micro/nanoscale structures are reported for the first time on silver using a dual-pulse femtosecond laser surface processing technique. The dual-pulse laser processing technique reported in this paper uses femtosecond laser pulse pairs with a controlled temporal delay between the leading and trailing pulses. Using dual pulses at higher fluence values, mound-like micro/nanostructures have been created on silver samples for the first time. Formation of the self-organized microstructures is shown to be dependent on the time delay between the leading and trailing pulses. Mound-like microstructures do not develop on silver for overlapped pulses or using single-pulse femtosecond laser surface processing for the parameter space studied. Subsurface microstructure characterization of a single mound-like surface structure is analyzed by cross-sectional analysis using focused ion beam milling followed by scanning electron microscopy and energy dispersive X-ray spectroscopy.
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Multiscale and Multidisciplinary Modeling, Experiments and Design (2018) 1:145–153
https://doi.org/10.1007/s41939-018-0011-2
ORIGINAL PAPER
Creation of micro/nano surface structures on silver using collinear
double femtosecond laser pulses with different pulse separation
Nicholas Roth1·Craig Zuhlke1·Edwin Peng2·Scott Hansen3·Jeffrey E. Shield2·Dennis Alexander1
Received: 27 March 2018 / Accepted: 9 April 2018 / Published online: 23 April 2018
© Springer International Publishing AG, part of Springer Nature 2018
Abstract
Self-organized mound-like micro/nanoscale structures are reported for the first time on silver using a dual-pulse femtosecond
laser surface processing technique. The dual-pulse laser processing technique reported in this paper uses femtosecond laser
pulse pairs with a controlled temporal delay between the leading and trailing pulses. Using dual pulses at higher fluence
values, mound-like micro/nanostructures have been created on silver samples for the first time. Formation of the self-organized
microstructures is shown to be dependent on the time delay between the leading and trailing pulses. Mound-like microstructures
do not develop on silver for overlapped pulses or using single-pulse femtosecond laser surface processing for the parameter
space studied. Subsurface microstructure characterization of a single mound-like surface structure is analyzed by cross-
sectional analysis using focused ion beam milling followed by scanning electron microscopy and energy dispersive X-ray
spectroscopy.
Keywords Femtosecond ·Laser ·Silver ·Materials ·Nanotechnology ·Functionalization
1 Introduction
Femtosecond laser surface processing (FLSP) is a develop-
ing technique for creating micro/nanoscale surfaces with a
wide range of applications including improved heat transfer
(Kruse et al. 2013,2015,2016), medical implants (Vorobyev
and Guo 2007), improving efficiency of electrolysis cells
(Anderson et al. 2015), and controlling material wetting prop-
erties (Zuhlke et al. 2013). In most of these applications, the
greatest enhancements result from a surface with a combi-
nation of micro and nanoscale surface features. Creation of
self-organized micro/nanoscale structures has been demon-
strated using FLSP for a range of metals including stainless
steel, titanium, nickel, and many other transition metals but
BNicholas Roth
Nicholas.roth@huskers.unl.edu
1Department of Electrical and Computer Engineering,
University of Nebraska–Lincoln, 209N Scott Engineering
Center, Lincoln, NE 68588, USA
2Department of Mechanical and Materials Engineering,
University of Nebraska–Lincoln, W342 Nebraska Hall,
Lincoln, NE 68588, USA
3EC6: Thermal Systems Branch, NASA Johnson Space
Center, 2101 NASA Parkway, Houston, TX 77058, USA
has been challenging in general for noble metals (Vorobyev
and Guo 2013). The difficulty in forming microscale surface
structures and the difference in structure formation on noble
metals versus other metals has not been adequately explained
and this paper explores the phenomena.
In this paper, a dual-pulse FLSP technique is used to
produce self-organized microscale mound-like structures on
silver with controlled temporal delay between the pulse
pairs. The mound-like structures are similar to the struc-
tures reported in the literature for other metals (Vorobyev
and Guo 2007; Kietzig et al. 2009; Kruse et al. 2013; Zuhlke
et al. 2013; Peng et al. 2017a,b). The dual-pulse technique
reported in this paper uses a similar experimental setup for
controlled temporal delay between pulse pairs as pump/probe
experiments used in time-resolved spectroscopy. The char-
acteristics of dual-pulse laser interactions have been studied
in the past in the context of laser-induced breakdown spec-
troscopy (LIBS) (Schiffern et al. 2007). Past experiments
show that overlapped double pulses result in an increased
ablation depth compared to double pulses with a delay greater
than 10 ps. Therefore, the energy does not go into removal of
material when a delay between pulses is introduced (Semerok
and Dutouquet 2004). The current consensus, in the literature
review, indicates this change in energy absorption for differ-
ent delay times is a result of plasma shielding from the first
123
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... The chaotic nature of fluid mechanics and redeposition creates structure interiors with voids. Figure 4.14 is an image adopted from a paper published covering this research [29]. This image compares an unprocessed silver surface shown in ...
... 21: Schematic of short pulse heating of solid-density plasma. Adopted from[29]. ...... 39 ...
... 14: SEM images adopted from[29] which show a) the grain boundary in unprocessed silver b) the grain boundary in dual pulse FLSP structures created in silver c) grain structure within bulk silver d) small and large pores within the silver structures. ...
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