• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.105.1-105.1
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• 2011

To enhance the performance of photovoltaic a-Si:H solar cells with a hybrid-type light absorbing structure of single crystal silicon nanoparticles (Si NPs) in a-Si:H matrix, single crystal Si NPs were produced by laser pyrolysis. The Si NPs were synthesized by $SiH_4$ gas decomposition using a $CO_2$ laser. The properties of Si NPs were controlled by process parameters such as $CO_2$ laser power, reactive gas pressure, and $H_2/SiH_4$ gas flows. The crystalline properties and sizes of Si NPs were analyzed by High Resolution Transmission Electron Microscopy (HRTEM). The sizes of Si NPs were controllable in the range of 5-15 nm in diameter and the effects of process parameters of laser pyrolysis were systematically investigated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.150-151
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• 2006

Laser pyrolysis is a very suitable method for the synthesis of a wide range of nanoparticles. A pilot unit based on this process has been recently developed at CEA. This paper reports results showing the possibility to produce SiC and $TiO_2$ nanoparticles at rates of respectively 1 and 0.2 kg/h and also the possibility to adjust the mean grain size of the particles and their structure by changing the laser intensity and reactants flow rates. First tests of liquid recovery have been also successfully performed to limit the risks of nanoparticles dissemination in the environement during their recovery.

• Korean Journal of Materials Research
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• v.23 no.5
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• pp.260-265
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• 2013

Silicon nanoparticle is a promising material for electronic devices, photovoltaics, and biological applications. Here, we synthesize silicon nanoparticles via $CO_2$ laser pyrolysis and study the hydrogen flow effects on the characteristics of silicon nanoparticles using high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-Vis-NIR spectrophotometry. In $CO_2$ laser pyrolysis, used to synthesize the silicon nanoparticles, the wavelength of the $CO_2$ laser matches the absorption cross section of silane. Silane absorbs the $CO_2$ laser energy at a wavelength of $10.6{\mu}m$. Therefore, the laser excites silane, dissociating it to Si radical. Finally, nucleation and growth of the Si radicals generates various silicon nanoparticle. In addition, researchers can introduce hydrogen gas into silane to control the characteristics of silicon nanoparticles. Changing the hydrogen flow rate affects the nanoparticle size and crystallinity of silicon nanoparticles. Specifically, a high hydrogen flow rate produces small silicon nanoparticles and induces low crystallinity. We attribute these characteristics to the low density of the Si precursor, high hydrogen passivation probability on the surface of the silicon nanoparticles, and low reaction temperature during the synthesis.

• Bulletin of the Korean Chemical Society
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• v.20 no.12
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• pp.1441-1446
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• 1999

Laser-induced fluorescence (LIF) spectroscopy has been applied to study the supersonic jet of radicals of nitric oxide (NO) and atomic iodine produced in the flash pyrolysis of precursors n-butylnitrite (CH₃(CH₂)₃ONO) and allyl iodide (C₃$H_5$I), respectively. The systematic population analysis with spectral simulations demonstrates that the precursors are efficiently pyrolyzed and that radical beams show a substantial supersonic cooling. In addition, absence of local equilibrium was observed in the distributions of two electronic spin-orbit states ²Π$_{1/2}$ and ²Π$_{3/2}$ of NO products and can be rationalized in terms of the efficiency of collision-induced energy transfer rates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.195-198
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• 2004

ZnO films were Prepared by ultrasonic spray Pyrolysis on MgO substrates. The surface morphology and crystallinity were observed as a function of substrate temperature by SEM and XRD, respectively. PL properties of the ZnO films were studied by using Cd-He laser. UV light around 3.37 eV was pronounced in the PL spectra. The origin of the PL peak was discussed.

• Laser Solutions
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• v.12 no.3
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• pp.7-13
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• 2009

The process of thermal-degradation of thin-film polymeris studied in this work for various laser sources from CW to fs. Samples composed of a thin polymer layer sandwiched between two glass plates are irradiated by the lasers and the threshold irradiance of polymer carbonization is experimentally measured. In the numerical analysis, the transient temperature distribution is calculated and the number density of carbonization in the polymer layer is also estimated. It is shown that pulsed lasers can result in more uniform distribution of temperature and carbonization than the CW laser.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.539-545
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• 2001

Undoped and Co$^{2+}$ $\alpha$-Ga$_2$S$_3$ thin films were grown by spray pyrolysis method. It has been found that these thin films have a monoclinic structure and direct optical energy gap and indirect were located to 3.477eV and 3.123 eV at 10K respectively. In the photoluminescence due to a D0A(donor-acceptor) pair recombination were observed at 502 nm and 671 nm for the $\alpha$-Ga$_2$S$_3$ thin film, where is excited by the 325 nm-line of He-Cd laser. These peaks are identified to be corresponding to the electron transition between the energy levels of Co$^{2+}$ ion sited a the T$_{d}$ symmetry point in the $\alpha$-Ga$_2$S$_3$;Co$^{2+}$ thin film. film.

• Carbon letters
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• v.9 no.1
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• pp.17-22
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• 2008

A carbon nanotube (CNT) of diameter ~20 nm has been synthesized by spray pyrolysis of turpentine oil using Ni/Fe catalyst. Pellet of CNTs has been used as a target to produce semiconducting carbon thin film of band gap 1.4 eV. Presence of oxygen pressure in the pulse laser deposition (PLD) chamber helped to control the $sp^3/sp^2$ ratio to achieve the desired band gap. Results are discussed with the help of Raman spectra, SEM TEM micrographs and optical measurements suggest that semiconducting carbon thin film deposited by PLD technique has retained its nanotubes structure except that its diameter has increased from 20 nm to 150 nm.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.905-908
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• 2011

We report fluorescence excitation and emission spectra of the CHBr molecule generated via pyrolysis of $CH_3Br$ in a molecular beam experiment. The 193 nm attenuation cross sections were estimated from the reduction of the CHBr signal as a function of the excimer laser fluence. The derived 193 nm absorption cross section for CHBr [$(3.24{\pm}0.59){\times}10^{-17}\;cm^2$] is slightly higher than the absorption cross section previously determined for CHCl [$(2.6{\pm}0.8){\times}10^{-17}\;cm^2$], but the difference is within the estimated uncertainties in the measured cross section.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.24-31
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• 2010

Laser carbonization of a polymer layer can be employed in various applications in the microelectronics industry, e.g repairing brightness pixels of an LCD panel. In this work, the process of thermal degradation of LCD color filter polymer by various laser sources with pulsewidths from CW to fs is studied. LCD pixels are irradiated by the lasers and the threshold irradiance of LCD color filter polymer carbonization is experimentally measured. In the numerical analysis, the transient temperature distribution is calculated and the number density of carbonization in the polymer layer is also estimated. It is shown that all the lasers can carbonize the polymer layers if the output power is adjusted to meet the thermal conditions for polymerization and that pulsed lasers can result in more uniform distribution of temperature and carbonization than the CW laser.