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Research Papers

Time-Resolved Experimental Study of Silicon Carbide Ablation by Infrared Nanosecond Laser Pulses

[+] Author and Article Information
Yibo Gao, Yun Zhou, Sha Tao

Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616

Benxin Wu1

Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616bwu11@iit.edu

Ronald L. Jacobsen

 Mound Laser and Photonics Center, Inc., Miamisburg, OH 45343

Bill Goodman

 Trex Enterprises Corporation, Albuquerque, NM 87107

1

Corresponding author.

J. Manuf. Sci. Eng 133(2), 021006 (Mar 11, 2011) (5 pages) doi:10.1115/1.4003618 History: Received August 24, 2010; Revised January 28, 2011; Published March 11, 2011; Online March 11, 2011

Silicon carbide, due to its unique properties, has many promising applications in optics, electronics, and other areas. However, it is difficult to micromachine using mechanical approaches due to its brittleness and high hardness. Laser ablation can potentially provide a good solution for silicon carbide micromachining. However, previous studies of silicon carbide ablation by nanosecond laser pulses at infrared wavelengths are very limited on material removal mechanism, and the mechanism has not been well understood. In this paper, experimental study is performed for silicon carbide ablation by 1064 nm and 200 ns laser pulses through both nanosecond time-resolved in situ observation and laser-ablated workpiece characterization. This study shows that the material removal mechanism is surface vaporization, followed by liquid ejection (which becomes clearly observable at around 1μs after the laser pulse starts). It has been found that the liquid ejection is very unlikely due to phase explosion. This study also shows that the radiation intensity of laser-induced plasma during silicon carbide ablation does not have a uniform spatial distribution, and the distribution also changes very obviously when the laser pulse ends.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the experimental system setup

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Figure 2

The laser ablation depth per pulse for silicon carbide (laser wavelength: 1064 nm and total pulse duration: 200 ns)

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Figure 3

The ICCD images of laser SiC ablation process from t=10 ns to 500 ns (the studied laser pulse starts at t=0, fluence per pulse: 57 J/cm2, ICCD gate width is 10 ns for t=10–300 ns, and 20 ns for t=500 ns, and workpiece target surface is located at the bottom of the images)

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Figure 4

The ICCD images of the laser SiC ablation process from t=300 ns to 5000 ns (the ejected liquid is pointed by arrows from t=1000 ns to 5000 ns, laser parameters are the same as Fig. 3, ICCD gate width is 10 ns for t=300 ns, 20 ns for t=500 ns, 50 ns for t=800–2000 ns, and 100 ns for t=3000–5000 ns, and workpiece surface is located at the bottom of the images)

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Figure 5

The maximum size of ejected liquid cloud during laser SiC ablation (shown in the ICCD image) versus the size of the ejected liquid redeposition zone on the target surface after ablation (shown in the SEM image) (laser fluence per pulse: 57 J/cm2 and the two sizes are consistent with each other)

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Figure 6

A SEM image of the same hole, as that shown in Fig. 5 (generated by laser ablation), at a higher magnification (magnification: ×2000 and scale bar: 10 μm)

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Figure 7

The calculated silicon carbide target temperature (unit: K) distribution at t=160 ns when the target surface temperature reaches the temporal maximum of ∼3963 K (laser fluence per pulse: 11 J/cm2 and target is in the x<0 region with the surface located at x=0)

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Figure 8

The transient front location of laser-induced plasma above the workpiece surface during silicon carbide ablation (laser fluence: 57 J/cm2 and the fitted curve is based on Eq. 2)

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