• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.96-101
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• 2001

In this study, diluted magnetic $Zn_{1-x}Mn_{x}Te$ epilayers were grown on GaAs(100) substrates by hot-wall epitaxy, and their characteristics were systematically examined. The maximum Mn composition of the $Zn_{1-x}Mn_{x}Te$ epilayers was 0.97. The crystallographic orientation was toward <100> and the structure of the $Zn_{1-x}Mn_{x}Te$ epilayers was the zincblende structure, identical to those of the GaAs substrate. With increasing the substrate temperature (350~$400^{\circ}C$), Mn composition increased (0.02~0.23) and he quality of the epilayer became worse. The lattice constants increased linearly with increasing Mn composition, but the band gap energy increased nonlinearly with increasing x.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.116-119
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• 2003

[ $Hg_{1-x}Cd_xTe$ ] (MCT) was grown by hot wall epitaxy method. Prior to the MCT growth, the CdTe (111) buffer layer was grown on the GaAs substrate at the temperature of 590 C for 15 min. When the thickness of the CdTe buffer layer was 5 m or thicker, the full width at half maximum values obtained from the x-ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe (111) /GaAs substrate at various temperature in situ. The crystal quality for those epilayers was investigated by means of the x-ray rocking curves and the photocurrent experiment. The photoconductor characterization for the epilayers was also measured. The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were turned out.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.18 no.1
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• pp.1-41
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• 1992

A new and unique class of nonionic surfactants was synthesized by reacting biological a-tocopherol with ethylene oxide for functional cosmetics. The structures were confirmed by Hl-UMR, FT-lR, TLC and elemental analysis. POV and conjugated diene value study for EPO showed POE(n)TE had antioxidative effect similar to tocopheryl acetate Protective effect on cell membrane in photohemolysis of POE(5)TE, POE(10)TE and POE(18)TE were slightly lower than tocopherol but higher than nonoxynol-12, and POE(10)TE had UV absorption power comparable with tocopherol and homosalate. Biological activity of the hydrophobic group of the new surfactants make them unique and different from those of conventional nonionic surfactants Systematic safety evaluations of POE(n)TEs on the skin and eye proved that they are as safe as tocopherol. The results of physicochemical study showed POE(10)TE had the lowest CMC value, POE(18)TE had the maximum surface tension reduction and the highest foam volume and POE(n)TEs had various HLB values by the degree of ethoxylation. The test resul Is of technological and practical applications of these surfactants for cosmetics showed some POE(n)TEs were superior to conventional surfactants. POE(5)TE in W/O emulsions, POE(10)TE and POE(12)TE in O/W emulsions, POE(12)TE in dispersions, POE(18)TE in solubilizations and POE(50)TE in gelations were shown to be excellent which was considered due to the structural characteristic and formation of liquid crystals of POE(n)TEs. By the development and applications of these excel lent multi-functional surfactants, innovative functional cosmetics were successfully formulated.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.369-373
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• 2005

High quality CdTe single crystal for the solar cell fabrication was grown by vertical Bridgman method. The etch pits patterns of (111) surfaces of CdTe etched by Nakagawa solution was observed the (111)A compesed of Cd atoms with typical triangle etch pits of pyramid mode. From the photoluminescence measurement on (111)A, we observed free exciton ($E_{x}$) existing only high quality crystal and neutal acceptor bound exciton ($A^{0}$,X) having very strong peak intensity. Then, the full width at half maximum and binding energy of neutral acceptor bound exciton were 7 meV and 5.9 meV, respectively. By Haynes rule, an activation enery of impurity was 59 meV. Therefore, the origins on impurity level acting as a neutral acceptor were associated Ag or Cu elements.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.154-158
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• 1999

Purpose : The purpose of this study was to find the optimum TE value for enhancing $T_2^{*}$ weighting effect and minimizing the SNR degradation and to compare the BOLD effects according to the changes of TE in 1.5T and 3.0T MRI systems. Materials and Methods : Healthy normal volunteers (eight males and two females with 24-38 years old) participated in this study. Each volunteer was asked to perform a simple finger-tapping task (sequential opposition of thumb to each of the other four fingers) with right hand with a mean frequency of about 2Hz. The stimulus was initially off for 3 images and was then alternatively switched on and off for 2 cycles of 6 images. Images were acquired on the 1.5T and 3.0T MRI with the FLASH (fast low angle shot) pulse sequence (TR : 100ms, FA : $20^{\circ}$, FOV : 230mm) that was used with 26, 36, 46, 56, 66, 76ms of TE times in 1.5T and 16, 26, 36, 46, 56, 66ms of TE in 3.0T MRI system. After the completion of scan, MR images were transferred into a PC and processed with a home-made analysis program based on the correlation coefficient method with the threshold value of 0.45. To search for the optimum TE value in fMRI, the difference between the activation and the rest by the susceptibility change for each TE was used in 1.5T and 3.0T respectively. In addition, the functional $T_2^{*}$ map was calculated to quantify susceptibility change. Results : The calculated optimum TE for fMRI was $61.89{\pm}2.68$ at 1.5T and $47.64{\pm}13.34$ at 3.0T. The maximum percentage of signal intensity change due to the susceptibility effect inactivation region was 3.36% at TE 66ms in 1.5T 10.05% at TE 46ms in 3.0T, respectively. The signal intensity change of 3.0T was about 3 times bigger than of 1.5T. The calculated optimum TE value was consistent with TE values which were obtained from the maximum signal change for each TE. Conclusion : In this study, the 3.0T MRI was clearly more sensitive, about three times bigger than the 1.5T in detecting the susceptibility due to the deoxyhemoglobin level change in the functional MR imaging. So the 3.0T fMRI I ore useful than 1.5T.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.1-8
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• 2008

Effects of annealing process in a reduction ambient on thermoelectric properties of the $(Bi,Sb)_{2}Te_3$ thin films prepared by thermal evaporation have been investigated. With annealing at $300^{\circ}C$ for 2 hrs in a reduction ambient(50% $H_2$+50% Ar), the crystallinity of the $(Bi,Sb)_{2}Te_3$ thin films were substantially improved with remarkable increase in the grain size. Seebeck coefficients of the $(Bi,Sb)_{2}Te_3$ thin films increased from$\sim90{\mu}V/K$ to $\sim180{\mu}V/K$ with annealing in the reduction ambient due to decrease in the hole concentration. Power factors of the $(Bi,Sb)_{2}Te_3$ thin films were remarkably improved for $5\sim16$ times with annealing in the reduction atmosphere. After annealing in the reduction ambient, a $(Bi,Sb)_{2}Te_3$ evaporated film exhibited a maximum power factor of $18.6\times10^{-4}W/K^{2}-m$.

• Korean Journal of Materials Research
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• v.33 no.7
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• pp.295-301
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• 2023

Thermoelectric (TE) energy harvesting, which converts available thermal resources into electrical energy, is attracting significant attention, as it facilitates wireless and self-powered electronics. Recently, as demand for portable/wearable electronic devices and sensors increases, organic-inorganic TE films with polymeric matrix are being studied to realize flexible thermoelectric energy harvesters (f-TEHs). Here, we developed flexible organic-inorganic TE films with p-type Bi_0.5Sb_1.5Te₃ powder and polymeric matrices such as poly(3,4-eethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and poly (vinylidene fluoride) (PVDF). The fabricated TE films with a PEDOT:PSS matrix and 1 wt% of multi-walled carbon nanotube (MWCNT) exhibited a power factor value of 3.96 µW·m^-1·K^-2 which is about 2.8 times higher than that of PVDF-based TE film. We also fabricated f-TEHs using both types of TE films and investigated the TE output performance. The f-TEH made of PEDOT:PSS-based TE films harvested the maximum load voltage of 3.4 mV, with a load current of 17.4 µA, and output power of 15.7 nW at a temperature difference of 25 K, whereas the f-TEH with PVDF-based TE films generated values of 0.6 mV, 3.3 µA, and 0.54 nW. This study will broaden the fields of the research on methods to improve TE efficiency and the development of flexible organic-inorganic TE films and f-TEH.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.9-15
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• 2007

Thermoelectric properties of the electrodeposited Bi-Te films and photoresist process have been investigated to apply for thermoelectric thin film devices. After plating in Bi-Te solutions of 20 mM concentration, which were prepared by dissolving $Bi_2O_3$ and $TeO_2$ into 1M $HNO_3$, thermoelectric properties of the films were characterized with variation of the Te/(Bi+Te) ratio in a plating solution. With increasing the Te/(Bi+Te) ratio in the plating solution from 0.5 to 0.65, Seebeck coefficient of Bi-Te films changed from $-59{\mu}V/K$ to $-48{\mu}V/K$ and electrical resistivity was lowered from $1m{\Omega}-cm$ to $0.8m{\Omega}-cm$ due to the increase in the electron concentration. Maximum power factor of $3.5{\times}10^{-4}W/K^2-m$ was obtained for the Bi-Te film with the $Bi_2Te_3$ stoichiometric composition. Using multilayer overhang process, the photoresist pattern to form thermoelectric legs of 30 m depth and 100m diameter was successfully fabricated fur micro thermoelectric device applications.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.353-359
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• 2000

$(Bi_{0.15}Sb_{0.85})_2Te_3$ and $(Bi_{1-x}Sb_x)_2Te_3$ thermoelectric thin films were prepared by magnetron sputtering process, and their thermoelectric characteristics were investigated with variation of the sputtering condition and the $Sb_2Te_3$ content. The $(Bi_{0.15}Sb_{0.85})_2Te_3$ film, deposited by DC sputtering at $300^{\circ}C$ with rotating the Corning glass substrate at 10 rpm, was fully crystallized to $(Bi,Sb)_2Te_3$ phase with c-axis preferred orientation. This $(Bi_{0.15}Sb_{0.85})_2Te_3$ film exhibited the Seebeck coefficient of 185 $\mu$V/K which was higher than the values of other $(Bi_{0.15}Sb_{0.85})_2Te_3$ films fabricated with different sputtering conditions. With increasing the $Sb_2Te_3$ content, the Seebeck coefficient and electrical resistivity of p-type $(Bi_{1-x}Sb_x)_2Te_3$ (0.77$\leq$x$\leq$1.0) film were lowered. Among p-type $(Bi_{1-x}Sb_x)_2Te_3$ films, a maximum power factor of $0.79{\times}10^{-3}W/K^2-m$ was obtained at (Bi_{0.05}Sb_{0.95})_2Te_3$ composition..

• Journal of the Microelectronics and Packaging Society
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• v.7 no.4
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• pp.1-5
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• 2000

Properties of AC applied hot pressed ($Pb_{1-x}Sn_{x}$) Te thermoelectrics were investigated. Mechanical alloying process used to produce alloyed powder to reduce the inhomogeneity and to avoid vaporization of constituents. It showed an increase in the mechanical alloying time with increasing of Sn contents in ($Pb_{1-x}Sn_{x}$)Te. ($Pb_{1-x}Sn_{x}$)Te were sintered at 873 to 923K for 1-4 minutes, under 150 kgf/$\textrm{cm}^2$ by AC applied hot pressng method. The short sintering time of AC applied hot pressing process could reduce the vaporization of Te. The density of ($Pb_{1-x}Sn_{x}$) Te was more dependent on the sintering temperature than the sintering time. The p-n transition was observed at x=0.1 but only p type conduction behavior was observed at more than 20 mol% of Sn compositions. The maximum value of Seebeck coefficient is 250 $\mu$V/K for x=0.2 at 500K. As the amount of Sn increases, the peak value of Seebeck coefficient drops and shifts to higher temperature and the peak value of electrical conductivity decreased with increasing temperature.