• Laser Solutions
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• v.12 no.1
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• pp.7-13
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• 2009

Engineering ceramics as sapphire are widely used in industry owing to their superior mechanical and corrosion properties. However, micromachining of sapphire is a considerable challenge due to its transparency. Recently, direct ablation of sapphire has been demonstrated with a visible laser pulse at sufficiently high laser intensity. In this work, the theoretical model for pulsed laser ablation of sapphire is suggested and numerical analysis is carried out using the model. Sapphire ablation begins with plasma generation by the laser interaction with surface defects, impurities and contaminations in the initial stage of machining. Subsequent absorption of the visible laser beam can be explained by three mechanisms: metalization of sapphire surface due to the EUV radiation from the hot plasma, increments of surface roughness and temperature-dependent absorption coefficient. Comparison of the computation results with experimental observation indicates that the proposed model of sapphire is reasonable.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.2
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• pp.43-47
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• 2003

Lead zirconate titanate (PZT) thin films were fabricated by the pulsed laser ablation deposition (PLAD) method onto Pt/Ti/SiO$_2$/Si substrates. Crystalline phases as well as preferred orientations in PZT films were investigated by X-ray diffraction analysis (XRD). The well-crystallized perovskite phase and the (101) preferred orientation were obtained by two-step annealing at the conditions of $650^{\circ}C$, 1 hour. It was found that the temperature for the pulsed laser ablated PZT films annealed via a two-step annealing process can be reduced 20$0^{\circ}C$ compared to that of the conventional three-step annealing temperature profile for enhancing the transformation of the perovskite phase. The remanent polarization and the coercive field of this film were about 20 $\mu$C/$\textrm{cm}^2$ and 46 kV/cm, while the dielectric constant and loss values measured at 1 KHz were approximately 860 and 0.04, respectively. The interesting phenomena of this film, such as vertical shift in hysteresis curve, are also discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.105-110
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• 2020

Radioactive Oxides are formed on the surface of the primary equipment in a nuclear power plant. In order to remove the oxide film that is formed on the surfaces of the equipment, chemical and physical decontamination technologies are used. The disadvantage of traditional technologies is that they produce secondary radioactive wastes. Therefore, in this study, the short-pulsed laser eco-friendly technology was used in order to reduce production of the secondary radioactive wastes. They were also used to minimize the damages that were caused on the base material and to remove the contaminated oxide film. The study was carried out using a Stainless steel 304 specimen that was coated with nickel-ferrite particles. Further, the laser source was selected with two different wavelengths. Furthermore, the depth of the coating layer was analyzed using a 3D laser microscope by changing the laser ablation conditions. Based on the analysis, the optimal conditions of ablation were determined using a 1064nm short-pulsed laser ablation technique in order to remove the radioactively contaminated oxide film from the irradiated stainless steel surface.

• Journal of Photoscience
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• v.6 no.3
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• pp.103-108
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• 1999

We present recent results on ablation mechanism, single-pulse laser micropatterning , pulsed-laser deposition(PLD) and particulates formation accompanying laser ablation, with special emplasis on polymers, in particular polymide, (PI), and polytetrafluoroethylene, (PTFE). Ablation of polymers is described on the basis of photothermal bond breaking within the bulk material. Here, we assume a first order chemical reaction, which can be described by an Arrhenius law. Ablation starts when the density of broken bonds at the surface reaches a certain critical value. Single-pulse laser ablation of polyimide shows a clear-length dependence of the threshold fluence. This experimental result strongly supports a thermal ablation model. We discuss the various possibilities and drawbacks of PLD and describe the morphology, physical properties and applications of PTFE films.

• Journal of Sensor Science and Technology
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• v.22 no.5
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• pp.357-363
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• 2013

An ultraviolet pulsed laser ablation of polyimide film coated with platinum has been used to enhance the sensitivity for the application as an electrochemical biosensor. Densely packed cones are formed on polyimide surface after UV irradiation which results in increase of surface area. In order to apply the sensitivity improvement of laser ablated polyimide film electrodes, the glucose oxidase modified biosensor was fabricated by using an encapsulation in the gel matrix through sol-gel transition of tetraethoxysliane on the surface of laser ablated polyimide film. The optimum conditions for glucose determination have been characterized with respect to the applied potential and pH. The linear range and detection limit of glucose detection were from 2.0 mM to 18.0 mM and 0.18 mM, respectively. The sensitivity of glucose biosensors fabricated with laser ablated polyimide film is about three times higher than that of plain polyimide film due to increase in surface area by laser ablation.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2004.10a
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• pp.90-94
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• 2004

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3909-3911
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• 2013

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.208-211
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• 2003

The dielectric carbon nitride thin films were deposited onto Si(100) using a pulsed laser ablation of pure graphite target combined with a high voltage discharge plasma in nitrogen gas atmosphere. We can be calculated dielectric constant, ${\varepsilon}_s$, with a capacitance Sobering bridge method. We reported to investigate the influence of the laser ablation of graphite target and DC high voltage source for the plasma. The properties of the deposited carbon nitride thin films were influenced by the high voltage source during the film growth. Deposition rate of carbon nitride films were found to increase drastically with the increase of high voltage source. Infrared absorption clearly shows the existence of C=N bonds and $C{\equiv}N$ bonds. The carbon nitride thin films were observed crystalline phase, as confirmed by x-ray diffraction data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.641-646
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• 2003

The dielectric carbon nitride thin films were deposited onto Si(100) substrate using a pulsed laser ablation of pure graphite target combined with a high voltage discharge plasma in the presence of a N$_2$ reactive gas. We calculated dielectric constant, $\varepsilon$$\_$s/, with a capacitance Schering bridge method. We investigated the influence of the laser ablation of graphite target and DC high voltage source for the plasma. The properties of the deposited carbon nitride thin films were influenced by the high voltage source during the film growth. Deposition rate of carbon nitride films were increased drastically with the increase of high voltage source. Infrared absorption clearly shows the existence of C=N bonds and C=N bonds. The carbon nitride thin films were observed crystalline phase confirmed by x-ray diffraction data.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3937-3938
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• 2012