• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.88-93
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• 1994

We fabricated a large-scale photovoltaic device for detecting-3-5$\mu$m IR, by forming of n$^{+}$-p junction in the $Hg_{1-x}Cd_{x}$Te (MCT) layer which was grown by LPE on CdTe substrate. The composition x of the MCT epitaxial layer was 0.295 and the hole concentration was 1.3${\times}10^{13}/cm^{4}$. The n$^{+}$-p junction was formed by B+ implantation at 100 keV with a does 3${\times}10^{11}/cm^{2}. The n$^{+}$ region has a circular shape with 2.68mm diameter. The vacuum-evaporated ZnS with resistivity of 2${\times}10^{4}{\Omega}$cm is used as an insulating layer over the epitaxial layer. ZnS plays the role of the anti-reflection coating transmitting more than 90% of 3~5$\mu$m IR. For ohmic contacts, gole was used for p-MCT and indium was used for n$^{+}$-MCT. The fabrication took 5 photolithographic masks and all the processing temperatures of the MCT wafer were below 90$^{\circ}C$. The R,A of the fabricated devices was 7500${\Omega}cm^{2}$. The carrier lifetime of the devices was estimated 2.5ns. The junction was linearly-graded and the concentration slope was measured to be 1.7${\times}10^{17}/{\mu}m$. the normalized detectivity in 3~5$\mu$m IR was 1${\times}10^{11}cmHz^{12}$/W, which is sufficient for real application.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.11
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• pp.490-492
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• 2005

A study on radiation hardening of infrared(IR) detector, the chief component of IR camera was performed. The radiation test on IR sensor passivated with the ZnS by Co$^{60}$ gamma-ray over 1 Mrads showed the reduction in Ro by 1/100 which was related to the noise level. This effect that was caused by carrier trapping in the ZnS passivation layer increased the leakage current and resulted in degradation in the device performance. For the radiation hardening of IR devices we suggested the ones with CdTe passivation layer which had a tendency to reluctant to carrier trapping in its layer and developed test patterns. Radiation test to the patterns showed that the our CdTe passivated device could survived over 1 Mrad gamma-ray dose.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.72-72
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• 2011

Surface science is intrinsically related to the performance of solar cells. In solar cells the generation and collection of charge carriers determines their efficiency. Effective transport of charge carriers across interfaces and minimization of their recombination at surfaces and interfaces is of utmost importance. Thus, the chemistry at the surfaces and interfaces of these devices must be determined, and related to their performance. In this talk we will discuss the role of two important interfaces, First, the role of surface passivation is very important in limiting the rate of carrier of recombination. Here we will combine x-ray photoelectron spectroscopy of the surface of a Si device with electrical measurements to ascertain what factors determine the quality of a solar cell passivation. In addition, the quality of the heterojunction interface in a ZnSe/CdTe solar cell affects the output voltage of this device. X-ray photoelectron spectroscopy gives some insight into the composition of the interface, while ultraviolet photoemission yields the relative energy of the two materials' valence bands at the junction, which controls the open circuit voltage of the solar cell. The relative energies of ZnSe and CdTe at the interface is directly affected by the material quality of the interface through processing.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4080-4092
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• 2021

In this study, the performance of sequence tracking methods for multiple interaction events in specific CdZnTe Compton imagers was evaluated using Monte Carlo simulations. The Compton imager consisted of a 6 × 6 array of virtual Frisch-grid CZT crystals, where the dimensions of each crystal were 5 × 5 × 12 mm³. The sequence tracking methods for another Compton imager that consists of two identical CZT crystals arrays were also evaluated. When 662 keV radiation was incident on the detectors, the percentages of the correct sequences determined by the simple comparison and deterministic methods for two sequential interactions were identical (~80%), while those evaluated using the minimum squared difference method (55-59%) and Three Compton method (45-55%) for three sequential interactions, differed from each other. The reconstructed images of a 662 keV point source detected using single and double arrays were evaluated based on their angular resolution and signal-to-noise ratio, and the results showed that the double arrays outperformed single arrays.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.49.2-49.2
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• 2007

• 한국전자현미경학회:학술대회논문집
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• 1995.06a
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• pp.42-43
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• 1995

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.39-43
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• 1998

Single crystals of{{{{ { Zn}_{ 1-x} {Mn }_{x }{Te} }}}} with x=0.3-0.6 were prepared by the standard Bridgeman method. Diffuse neutron diffraction intensities due to the short range magnetic ordering is found in the vicinities of 1 1/2 0 reciprocal point and its equivalent point, indicating that the magnetic correlation of the clusters is the type III antiferromangetic one do the F-type Bravais class crystals, being identical with that of {{{{{ Cd}_{ 1-x} {Mn }_{x }Te }}}}. Neutron inelastic scattering measure-ment has been performed for {{{{{ Zn}_{ 0.6} { Mn}_{ 0.4}Te }}}} sample using the cold neutron spectrometer. AGNES. High resolution measurement with the energy resolution of {{{{ TRIANGLE E= +- .01meV}}}} was carried out in the temperature range from 10K to the ambient. Critical scattering, closely related with the spin glass transition, has been observed for the first time in this semimagnetic semi-conductor. The critical scattering is observed at temperatures in the vicinity of the spin glass transition temperature, 17K. The scattering is observed as a kind of quasielastic scattering in the reciprocal range where the elastic magnetic diffuse scattering has been observed, e.g., 11/20 reciprocal point, indicating the spin fluctuation has dynamic components in this material. Photoconductivity has been discovered below 150K in {{{{{ Zn}_{ 0.4} {Mn }_{0.6 } Te}}}}. The electric AC conductivity has been increased dramatically under the laser light with the wave lengths of {{{{ lambda =6328,5145 and4880 }}}}$\AA$ ,respectively. After the light was darkened, the conductivity was reduced to the original level after about 2000 seconds at 50K, being above the spin glass transition temperature. This phenomenon is the typical persistent photoconductivity; PPC which was similarly found in {{{{ { Zn}_{ 1-x} { Mn}_{x} Te}}}}.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.567-572
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• 2011

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (${\alpha}$ particle and gamma-ray) emitted from an $^{241}Am$ source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector ($5{\times}5{\times}2\;mm^3$) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from ${\alpha}$ particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (${\mu}{\tau}$) products; the ${\alpha}$ particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the ${\alpha}$ particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than ${\alpha}$ particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.27-33
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• 2001

In order to study the long-term change of heavy metal concentrations in the Kumho river water, water analysis was conducted at 13sites surrounding the Kumho river system for 18times from September 1993 to August 1999. Analytical items for the study of water quality are Cu, Zn, Cd, Cr, Fe, Mn and Pb. The six year term studied in this work was divided into Part I and Part II, which covers the period from September 1993 to August 1996 and the period from September 1996 to August 1999, respectively. The mean concentrations of Cu, Zn, Cd, Cr, Fe, Mn and Pb in the unit of ppm for the Part I period showed 0.032, 0.025, 0.006, 0.050, 0.053 and 0.019, respectively. The mean concentrations of Cu, Zn, Cd, Cr, Fe, Mn and Pb in the unit of ppm for the Part II period showed 0.001, 0.001, 0.001, 0.004, 0.020, 0.002 and 0.002, respectively. The heavy metal concentrations in the Kumho river water for te second period were found to be decreased by 1/32, 1/25, 1/6, 1/1.5, 1/2.5, 1/26.5 and 1/9.5 for Cu, Zn, Cd, Cr, Fe, Mn and Pb, respectively. The present results clearly indicate that the water quality in the Kumho river is improving in terms of heavy metal contaminations.

• Economic and Environmental Geology
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• v.43 no.5
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• pp.491-503
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• 2010

Geochemical characteristics of the Moisan epithermal gold-silver deposit with total 140 samples in Haenam area, Jeollanamdo were studied by using multivariate statistical analysis (correlation analysis, factor analysis and cluster analysis). The correlation analysis reveals that Ag, Cu, Bi, Te are highly correlated with Au in the both non-mineralized and mineralized zone. It is resulted from the presence of Au-Ag bearing minerals (electrum, sylvanite, calaverite and stuezite) and non Au-Ag containing minerals (chalcopyrite, tellurobismuthite and bismuthinite). Mo shows relatively much higher correlation at the mineralized zone (0.615) than non-mineralized zone (0.269) which implies Mo content is strongly affected by Au-mineralization. While Mn, Cs, Fe, Se correlated with Au at the nonmineralized zone, they have negative correlation at the mineralized zone. Therefore, they seem to be eluviated elements from the host rock during gold mineralization. Sb is enriched during the gold mineralization showing high correlation at the mineralized zone and negative correlation at the non-mineralized zone. According to the factor analysis, Se, Ag, Cs, Te are the indicators of gold mineralization presence due to the strong affection of gold content in the non-mineralized zone. In the mineralized zone, on the other hand, Mo, Te and Sb, Cu are the indicators of gold and silver mineralization, respectively. While the cluster analysis reveals that Cd-Zn-Pb-S, Bi-Fe-Cu-Mn, Se-Te-Au-Cs-Ag, As-Sb-Ba are the similar behavior elements groups in the non-mineralized zone, Cd-Zn-Mn-Pb, Fe-S-Se, As-Bi-Cs, Ag-Sb-Cu, Au-Te-Mo are the similar behavior elements groups in the mineralized zone. Using multivariate statistical analysis as mentioned above makes it possible to compare the behavior of presented minerals and difference of geochemical characteristics between mineralized and non-mineralized zone. Therefore, it will be expected a useful tool on the similar type of mining exploration.