• 한국재료학회지
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• 제12권9호
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• pp.724-728
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• 2002

Inductively-coupled $N_2$O plasma was utilized to grow silicon dioxide at low temperature and applied to fabricate polycrystalline-silicon thin film transistors. At $400^{\circ}C$, the thickness of oxide was limited to 5nm and the oxide contained Si≡N and ≡Si-N-Si≡ bonds. The nitrogen incorporation improved breakdown field to 10MV/cm and reduced the interface charge density to $1.52$\times$10^{11}$ $cm^2$ with negative charge. The $N_2$O plasma gate oxide enhanced the field effect mobility of polycrystalline thin film transistor, compared to $O_2$ plasma gate oxide, due to the reduced interface charge at the $Si/SiO_2$ interface and also due to the reduced trap density at Si grain boundaries by nitrogen passivation.

• 한국세라믹학회지
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• 제49권6호
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• pp.631-636
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• 2012

Conventional SONOS (poly-silicon/oxide/nitride/oxide/silicon) type memory is associated with a retention issue due to the continuous demand for scaled-down devices. In this study, $Al_2O_3/Y_2O_3/SiO_2$ (AYO) multilayer structures using a high-k $Y_2O_3$ film as a charge-trapping layer were fabricated for nonvolatile memory applications. This work focused on improving the retention properties using a $Y_2O_3$ layer with different tunnel oxide thickness ranging from 3 nm to 5 nm created by metal organic chemical vapor deposition (MOCVD). The electrical properties and reliabilities of each specimen were evaluated. The results showed that the $Y_2O_3$ with 4 nm $SiO_2$ tunnel oxide layer had the largest memory window of 1.29 V. In addition, all specimens exhibited stable endurance characteristics (program/erasecycles up to $10^4$) due to the superior charge-trapping characteristics of $Y_2O_3$. We expect that these high-k $Y_2O_3$ films can be candidates to replace $Si_3N_4$ films as the charge-trapping layer in SONOS-type flash memory devices.

• E2M - 전기 전자와 첨단 소재
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• 제9권1호
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• pp.30-37
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• 1996

Previously, crystallization of a-Si:H films on glass substrates were limited to anneal temperature below 600.deg. C, over 10 hours to avoid glass shrinkage. Our study indicates that the crystallization is strongly influenced by anneal temperature and weakly affected by anneal duration time. Because of the high temperature process and nonconducting substrate requirements for poly-Si TFTs, the employed substrates were limited to quartz, sapphire, and oxidized Si wafer. We report on poly-Si TFT's using high temperature anneal on a Si:H/Mo structures. The metal Mo substrate was stable enough to allow 1000.deg. C anneal. A novel TFT fabrication was achieved by using part of the Mo substrate as drain and source ohmic contact electrode. The as-grown a-Si:H TFT was compared to anneal treated poly-Si TFT'S. Defect induced trap states of TFT's were examined using the thermally stimulated current (TSC) method. In some case, the poly-Si grain boundaries were passivated by hydrogen. A-SI:H and poly-Si TFT characteristics were investigated using an inverted staggered type TFT. The poly -Si films were achieved by various anneal techniques; isothermal, RTA, and excimer laser anneal. The TFT on as grown a-Si:H exhibited a low field effect mobility, transconductance, and high gate threshold voltage. Some films were annealed at temperatures from 200 to >$1000^{\circ}C$ The TFT on poly-Si showed an improved $I_on$$I_off$ ratio of $10_6$, reduced gate threshold voltage, and increased field effect mobility by three orders. Inverter operation was examined to verify logic circuit application using the poly Si TFTs.

• 한국전기전자재료학회논문지
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• 제13권11호
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• pp.914-920
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• 2000

When the charge-trap type SONOS(polysilicon-oxide-nitride-oxide-semiconductor) cells are used to flash memory, the tunneling program/erase condition to minimize the generation of interface traps was investigated. SONOSFET NVSM(Nonvolatile Semiconductor Memory) cells were fabricated using 0.35 ㎛ standard memory cell embedded logic process including the ONO cell process, based on retrograde twin-well, single-poly, single metal CMOS(Complementary Metal Oxide Semiconductor) process. The thickness of ONO triple-dielectric for the memory cell is tunnel oxide of 24 $\AA$, nitride of 74 $\AA$, blocking oxide of 25 $\AA$, respectively. The program mode(V$\_$g/=7, 8, 9 V, V$\_$s/=V$\_$d/=-3 V, V$\_$b/=floating) and the erase mode(V$\_$g/=-4, -5, -6 V, V$\_$s/=V$\_$d/=floating, V$\_$b/=3 V) by MFN(Modified Fowler-Nordheim) tunneling were used. The proposed programming condition for the flash memory of SONOSFET NVSM cells showed less degradation(ΔV$\_$th/, S, G$\_$m/) characteristics than channel MFN tunneling operation. Also, the program inhibit conditins of unselected cell for separated source lines NOR-type flash memory application were investigated. we demonstrated that the phenomenon of the program disturb did not occur at source/drain voltage of 1 V∼12 V and gate voltage of -8 V∼4 V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.20-20
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• 2007

Nanowire-based field-effect transistors (FETs) decorated with nanoparticles have been greatly paid attention as nonvolatile memory devices of next generation due to their excellent transportation ability of charge carriers in the channel and outstanding capability of charge trapping in the floating gate. In this work, top-gate single ZnO nanowire-based FETs with and without Au nanoparticles were fabricated and their memory effects were characterized. Using thermal evaporation and rapid thermal annealing processes, Au nanoparticles were formed on an $Al_2O_3$ layer which was semi cylindrically coated on a single ZnO nanowire. The family of $I_{DS}-V_{GS}$ curves for the double sweep of the gate voltage at $V_{DS}$ = 1 V was obtained. The device decorated with nanoparticles shows giant hysterisis loops with ${\Delta}V_{th}$ = 2 V, indicating a significant charge storage effect. Note that the hysterisis loops are clockwise which result from the tunneling of the charge carriers from the nanowire into the nanoparticles. On the other hand, the device without nanoparticles shows a negligible countclockwise hysterisis loop which reveals that the influence of oxide trap charges or mobile ions is negligible. Therefore, the charge storage effect mainly comes from the nanoparticles decorated on the nanowire, which obviously demonstrates that the top-gate single ZnO nanowire-based FETs decorated with Au nanoparticles are the good candidate for the application in the nonvolatile memory devices of next generation.

• 한국전기전자재료학회논문지
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• 제24권6호
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• pp.473-479
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• 2011

In this paper, we have compared amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) with the nano-crystalline embedded-IGZO ($N_c$-embedded-IGZO) TFT fabricated by solid-phase crystallization (SPC) technique. The field effect mobility (${\mu}_{FE}$) of $N_c$-embedded-IGZO TFT was 2.37 $cm^2/Vs$ and the subthreshold slope (S-factor) was 0.83 V/decade, which showed lower performance than those of a-IGZO TFT (${\mu}_{FE}$ of a-IGZO was 9.67 $cm^2/Vs$ and S-factor was 0.19 V/decade). This results originated from generation of oxygen vacancies in oxide semiconductor and interface between gate insulator and semiconductor due to high temperature annealing process. However, the threshold voltage shift (${\Delta}V_{TH}$) of $N_c$-embedded-IGZO TFT was 0.5 V, which showed 1 V less shift than that of a-IGZO TFT under constant current stress during $10^5$ s. This was because there were additionally less increase of interface trap charges in Nc-embedded-IGZO TFT than a-IGZO TFT.

• 한국약용작물학회지
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• 제23권2호
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• pp.117-124
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• 2015

Osteoporosis induces a bone mineral density loss due to imbalance of bone homeostasis that is achieved by osteoclasts (which are involved in bone resorption) and osteoblasts (which are involved in bone formation). Thus, this study was performed to evaluate the effects of hot water extract of the Achyranthes bidentata Blume (ABB) and Panax ginseng (Gin) on osteoclast and osteoblast differentiation. In this study, there was no cytotoxicity by ABB, 50 and $100{\mu}g/ml$ of Gin significantly decreased cell viability of RANKL-induced osteoclast in RAW264.7 cell (p < 0.01). But, it was $50{\mu}g/ml$ of ABB and Gin mixtures increased due to protective action of ABB. Furthermore, Gin contained groups (Gin, ABB and Gin mixtures) were inhibitory effects on osteoclast differentiation and bone resorption, and increased in osteoblast differentiation activity. Gin clearly inhibited RANKL-induced osteoclast differentiation by decreased calcitonin and TRAP (p < 0.01). Also, these extracts significantly increased calcium accumulation formation of osteoblastic differentiation reagents-induced osteoblast in MC3T3-E1 cell (p < 0.05). These results suggest that ABB and Gin mixtures may be a potential as drug for the treatment of osteoporosis.

• Journal of Ginseng Research
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• 제43권1호
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• pp.27-37
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• 2019

Background: The structural conversions in ginsenosides induced by steaming or heating or acidic condition could improve red ginseng bioactivities significantly. In this paper, the chemical transformations of red American ginseng from fresh Panax quinquefolium L. under steaming were investigated, and the possible mechanisms were discussed. Methods: A method with reversed-phase high-performance liquid chromatography coupled with linear ion trap mass spectrometry ($HPLC-MS^n$)-equipped electrospray ionization ion source was developed for structural analysis and quantitation of ginsenosides in dried and red American ginseng. Results: In total, 59 ginsenosides of protopanaxadiol, protopanaxatriol, oleanane, and ocotillol types were identified in American ginseng before and after steaming process by matching the molecular weight and/or comparing $MS^n$ fragmentation with that of standards and/or known published compounds, and some of them were determined to be disappeared or newly generated under different steaming time and temperature. The specific fragments of each aglycone-type ginsenosides were determined as well as aglycone hydrated and dehydrated ones. The mechanisms were deduced as hydrolysis, hydration, dehydration, and isomerization of neutral and acidic ginsenosides. Furthermore, the relative peak areas of detected compounds were calculated based on peak areas ratio. Conclusion: The multicomponent assessment of American ginseng was conducted by $HPLC-MS^n$. The result is expected to provide possibility for holistic evaluation of the processing procedures of red American ginseng and a scientific basis for the usage of American ginseng in prescription.

• 한국재료학회지
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• 제29권8호
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• pp.463-468
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• 2019

The electrical and interfacial properties of $HfO_2/Al_2O_3$ and $Al_2O_3/HfO_2$ dielectrics on AlN/p-Ge interface prepared by thermal atomic layer deposition are investigated by capacitance-voltage(C-V) and current-voltage(I-V) measurements. In the C-V measurements, humps related to mid-gap states are observed when the ac frequency is below 100 kHz, revealing lower mid-gap states for the $HfO_2/Al_2O_3$ sample. Higher frequency dispersion in the inversion region is observed for the $Al_2O_3/HfO_2$ sample, indicating the presence of slow interface states A higher interface trap density calculated from the high-low frequency method is observed for the $Al_2O_3/HfO_2$ sample. The parallel conductance method, applied to the accumulation region, shows border traps at 0.3~0.32 eV for the $Al_2O_3/HfO_2$ sample, which are not observed for the $Al_2O_3/HfO_2$ sample. I-V measurements show a reduction of leakage current of about three orders of magnitude for the $HfO_2/Al_2O_3$ sample. Using the Fowler-Nordheim emission, the barrier height is calculated and found to be about 1.08 eV for the $HfO_2/Al_2O_3$ sample. Based on these results, it is suggested that $HfO_2/Al_2O_3$ is a better dielectric stack than $Al_2O_3/HfO_2$ on AlN/p-Ge interface.

• Journal of Applied Biological Chemistry
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• 제62권1호
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• pp.73-79
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• 2019

A novel esterase gene (est7S) was cloned from an enriched metagenomic library derived from an oil-spill area. The gene encoded a protein of 505 amino acids, and the molecular mass of the Est7S was estimated to be 54,512 Da with no signal peptide. Est7S showed the highest identity of 40% to an esterase from a sludge metagenome compared to the characterized enzymes with their properties, although it showed 99% identity to a carboxylesterase in the genome sequence of Alcanivorax borkumensis SK2. Est7S had catalytic triad residues, Ser183, Glu312, and His420, and the GESAG motif in most family VII lipolytic enzymes. Est7S was purified from the crude extract of clone SM7 using Sephacryl S-200 HR and HiTrap Q column chromatographies. The purified Est7S was optimally active at $50^{\circ}C$ and pH 10.0. Est7S showed a high specific activity of 366.7 U/mg protein. It preferred short length esters, particularly p-nitrophenyl acetate, efficiently hydrolyzed R- and S-enantiomers of methyl-3-hydroxy-2-methylpropionate, and glyceryl tributyrate. These properties of Est7S may provide potential merits in biotechnological applications such as detergent and paper processing under alkaline conditions.