• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.5 s.347
• /
• pp.25-33
• /
• 2006

We have extracted the material parameters such as absorption coefficients of GaN, $Al_{0.2}Ga_{0.8}N$, and Schottky contact metal Ni of Schottky Diode UV-A and B detectors using a transfer matrix method (TMM). The ratios of the absorbed light to the total incident amount at the depletion regions of GaN and $Al_{0.2}Ga_{0.8}N$ have been calculated in order to obtain the spectral responsivity. Absorption coefficients of the materials have been obtained by fitting the simulated data with measured data. The depletion layer thickness has been obtanied by capacitance-voltage measurement. The results pave the way for the optimum design of UV Schottky detectors. Since the absorption coefficient of the Ni electrode is very high, its thickness is a major factor that determines the responsivity. It is possible to attain improved UV detectors using thinnest possible Ni electrodes and wide depletion regions of GaN and $Al_{0.2}Ga_{0.8}N$.

• Journal of the Korean Ceramic Society
• /
• v.41 no.5
• /
• pp.359-363
• /
• 2004

Photoluminescence excitation (PLE) spectroscopy studies were performed for anodically etched porous Zn, which exhibited a PL in the blue/violet spectral range peaking at 420 nm (2.95 eV), and oxidzed porous Zn at 380$^{\circ}C$ for 10 min and 12 h. A broad absorption band was observed at 4.07 eV (305 nm), 3.49 (355 nm) for anodically etched porous Zn. In contrast, both the oxidized porous Zn and sintered ZnO exhibited an almost identical one broad absorption band at 3.85 eV (322 nm), when PLE spectra were measured at 378 nm (3.28 eV). The oxidized porous Zn and sintered ZnO, which displayed both UV and green luminescence band, showed an additional absorption band at 389 nm (3.19 eV) and 467 nm (2.66 eV). In contrast, no significant absorption band was detected for a 10-min oxidized porous Zn, which only displayed one UV luminescence void of deep-level luminescence. These absorption bands determined by PLE studies enabled a clear understanding of an emission mechanism for the UV and green luminescence from ZnO.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.15 no.3
• /
• pp.114-119
• /
• 2005

This study has been carried out with the eight HPHT processed NOUV diamonds - two yellow, two yellowish green, two green and two orangy yellow color stones. The gemological properties of these diamonds included a highly saturated body color, graphitized fractures around the girdles, tension cracks around crystalline inclusions, long-wave UV with medium yellowish green to a very strong yellowish green luminescence, and short-wave UV with faint yellowish green to a strong yellowish green luminescence. Distinctive features of spectroscopic properties include absorption peaks at 415 nm and 503 nm a strong absorption band at $460{\sim}480nm$ and a H2 center at 986nm. Infrared spectra showed an absorption peak at $1344cm^{-1}$ (C center), which is the characteristics related to single substitutional nitrogen.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.3
• /
• pp.327-340
• /
• 1996

In this study, a series of $LiNbO_{3}$ crystals with different [Li]/[Nb] ratios, congruent $LiNbO_{3}$ crystals with doped Mg and with Mg and codoped with Mn were grown by the Czocharalski method. These were investigated by UV and IR spectrophotometry. Stoichiometry dependences of the UV absorption edge and the $OH^{-}$ absorption spectra were studied with different [Li]/[Nb] ratios. The position of the UV absorption edge adn the shape and peak point of the $OH^{-}$ absorption spectra changed monotonously upto a critical concentration of Mg ions. The mechanism of the incorporation of Mg ions changes at this concentration. The decomposition of the $OH^{-}$ absorption spectra using a Gaussian lineshape function showed that in Li-deficient crystals the absorption spectra consist of five components in contrast to more or less perfect stoichiometric crystals which reveal to three components. On the basis of these results, the intrinsic and the extrinsic defect structure models in $LiNbO_{3}$ crystals were examined. The behaviour of $\nu$ (OH) reflects the defect structure and supports the Li-site vacancy model as the intrinsic defect structure model and the corresponding extrinsic defect model. A brief discussion is also given of the behaviour of $\nu$ (OH) in $LiNbO_{3}$ crystals simultaneously doped with several kinds of impurity.

• Journal of Korean Ophthalmic Optics Society
• /
• v.4 no.2
• /
• pp.57-63
• /
• 1999

The optical absorption and transmittance of cow' crystalline were measured by spectrophotometer in the 200~800nm wavelength regions. The optical absorptions of crystalline composed of a high absorption band in the UV-A, UV-B, and appeared the light transmittance edge in the 400nm wavelength region, and completely transmitted without the absorption in the high wavelength regions than 400nm. Also, the optical absorption and transmittance had no temperature dependence. The optical transmittance spectrum of crystalline concord with the thin film structure of $n_0/(0.5H)L(LH)^6(0.5H)/n_s$ and $n_0{\mid}(0.5LH0.5L)^kL/1.25{\mid}4.0$ of long-pass edge filter form. In the artificial crystalline and inter lens layout, long-pass edge filter layout can UV cut off.

• Journal of the Korean Chemical Society
• /
• v.34 no.6
• /
• pp.616-621
• /
• 1990

The spectrophotometric methods for the determination of Nd, Pr, Sm, Eu, Ho, Er were developed, using the multicomponent method of absorption spectra cointerference. The absorption spectra of individual Nd, Pr, Sm, Eu, Ho, Er, mixture of Sm, Eu, Ho, Er in hydrochloric acid solutions were investigated, and also a band register which includes the molar absorptions for all trivalent Nd, Pr, Sm, Eu, Ho and Er absorption band maxima were measured. The spectrophotometric determination of Nd, Pr, Sm, Eu, Ho and Er were investigated using the analytically significant absorption bands at 444.2, 575.1, 401.7, 394.2, 416.6, and 379.7 nm, respectively.

• Journal of Environmental Health Sciences
• /
• v.28 no.5
• /
• pp.59-64
• /
• 2002

The photocatalytic decolorization of the Rhodamine B (RhB) was studied using a UV/TiO$_2$ reactor. Yakuri titanium dioxide(anatase) was used as the suspended photocatalyst and proved to be effective for decolorization irradiated with UV light (254 mm). The photocatalyzed dioxide concentrations, light intensity and air flow rates. In 0.01 mM RhB, color could be completely photodegraded after 3 hours. Absorption spectrum of an aqueous solution containing RhB showed a continued diminution of the RhB concentration in the solution bulk : concomitantly, no new absorption peaks appeared. This confirmed the decolorization of RhB, i.e., the break up of the chromopore. The optimum loaded titanium dioxide for the decolorization was 0.75 g/(equation omitted). The light intensity showed exponential decay with distance. The decay of light intensity of RhB solution showed different tendency from TiO$_2$. These results suggested that the photocatalytic decolorization of dyes may be available method for decolorizing in wastewater.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.12
• /
• pp.2382-2388
• /
• 2007

A series of dimethine cyanine dyes were synthesized in a fast, efficient and high yield by the condensation of quaternary salts with 1H-indole-3-carbaldehyde in the presence of piperidine under solvent-free microwave irradiation. The products were identified by 1H NMR, IR, UV-Vis spectra and elemental analysis. The absorption and fluorescence properties of these dyes were investigated both experimentally and theoretically. Calculations performed at a combination of time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) reproduced the π-π* type absorption bands of the dyes. Regression analysis was used for studying theoretical results of the absorption maxima in different solvents. Compared with experimental counterparts, estimated overall uncertainties in the absorption maxima were about ±2%.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1997.10a
• /
• pp.111-115
• /
• 1997

Iron-doped LiNbO$_3$ crystals were grown by floating zone(FZ) method with different [Li]/[Nb] ratio in order to investigate doping effects of transition metal impurity in LiNbO$_3$ crystal. The grown crystals were analyized edge in UV/VIS/IR spectrometry and EPMA(electron probe micro-analysis). The absorption edge in UV-VIS region and OH-absorption peak in IR region were investigated. The change of Fe concentration along the solidification direction was also investigated

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.1
• /
• pp.62-67
• /
• 2012

Recently UV laser is widely used to process micro parts using various materials such as polymers, metals and ceramics because it has a very high intensity at the focused spot area. It is generally known that there are still some difficulties for alumina($Al_2O_3$) ceramics to directly make micro patterns like holes and lines on the surface of working material using 355nm UV laser because the alumina has a very low absorption coefficient at that wavelength. But nowadays new alumna with nano-porous holes is developed and applied to advanced micro functional parts of IT, BT and BT industries. In this paper, we are going to show the mechanism of photo-thermal ablation for nano-porous ceramics. Inside hole there is a lot of multiple reflections along the depth of hole. Experimentally we can find the micro hole drilling and micro grooving on the surface of nano-porous alumina.