• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.149-153
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• 2006

An attempting to produce a p-type diluted magnetic semiconductor (DMS) using $Ti_{1-x}Co_xO_{2-\delta}-based$ thin films was made by suitable control of the deposition parameters including deposition temperature, deposition pressure, and doping level using a pulsed laser deposition method. T$Ti_{0.97}Co_{0.03}O_{2-\delta}-based$ (TCO) films deposited at $500^{\circ}C$ at a pressure of $5\times10^{-6}$ Torr showed an anomalous Hall effect with p-type characteristics. On the other hand, films deposited at $700^{\circ}C$ at $5\times10^{-6}$ Torr showed n-type behaviors by a decreased solubility of cobalt. The charge carrier concentration in the p-type TCO films was approximately $7.9\times10^{22}/cm^3$ at 300 K and the anomalous Hall effect in the p-type TCO films was controlled by a side-jump scattering mechanism. The magnetoresistance (MR), measured at 5 K in p-type TCO films showed a positive behavior in an applied magnetic field and the MR ratio was approximately 3.5 %. The successful preparation of p-type DMS using the TCO films has the potential for use in magnetic tunneling junction devices.

• Journal of Life Science
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• v.14 no.2
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• pp.362-367
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• 2004

For better understanding of the host infection mechanism of Vibrio, a Vibrio parahaemolyticus collagenase mutant was generated by insertional inactivation of a vppC gene encoding extracellular collagenase. A recombinant DNA containing vppC::nptII was cloned into a suicide plasmid pDMS197, resulted in pVCM03. The recombinant suicide plasmid pVCM03 contained in E. coli $\chi$7213 was transferred to a wild-type V. parahaemolyticus 04 through conjugation. The recombinant vppC::nptII DNA in pVCM03 was exchanged with wild-type allele by homologous recombination resulting vppC mutant, V. parahaemolyticus CM. The mutant was selected and screened on TCBS media containing 10% sucrose and kanamycin. The mutation by allele exchange was confirmed with the comparison of the size of DNAs amplified by PCR. V. parahaemolyticus CM showed at least 4-fold less collagen-degrading activity than those of wild-type, and the mutant exhibited less cytotoxicity than that of wild-type in MTT assay.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.314-314
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• 2012

The dilute magnetic semiconductors (DMS) have been developed to multi-functional electro-magnetic devices. Specially, the Si based DMS formed by ion implantation have strong advantages to improve magnetic properties because of the controllable effects of carrier concentration on ferromagnetism. In this study, we investigated the deep level states of Fe- and Co-ions implanted Si wafer during rapid thermal annealing (RTA) process. The p-type Si (100) wafers with hole concentration of $1{\times}10^{16}cm^{-3}$ were uniformly implanted by Fe and Co ions at a dose of $1{\times}10^{16}cm^{-2}$ with an energy of 60 keV. After RTA process at temperature ranges of $500{\sim}900^{\circ}C$ for 5 min in nitrogen ambient, the Au electrodes with thickness of 100 nm were deposited to fabricate a Schottky contact by thermal evaporator. The surface morphology, the crystal structure, and the defect state for Fe- and Co- ion implanted p-type Si wafers were investigated by an atomic force microscopy, a x-ray diffraction, and a deep level transient spectroscopy, respectively. Finally, we will discuss the physical relationship between the electrical properties and the variation of defect states for Fe- and Co-ions implanted Si wafer after RTA.

• Journal of Life Science
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• v.33 no.9
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• pp.713-723
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• 2023

Lung cancer is a type of cancer that has the highest mortality rate. It is mainly classified into small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC). Chemotherapy is used to treat lung cancer, but long-term treatment causes side effects and drug resistances. Curcumin is a bright yellow polyphenol extracted from the root of turmeric. It has biological activities, such as anti-oxidant, anti-cancer, and anti-inflammatory effects. In this study, we observed differential cell death in human lung cancer cells. Based on the results, curcumin at 10, 30, and 50 μM exhibited a dose-dependent inhibition on the cell survival of several lung cancer cells, with minor differential phenotypes. In addition, apoptosis, autophagy, and reactive oxygen species (ROS) regeneration were observed through flow cytometry. Curcumin dose-dependently increased these phenotypes in A549 (NSCLC) and DMS53 (SCLC), which were restored by corresponding inhibitors. Western blotting was performed to measure the level of expression of apoptosis- and autophagy-related proteins. The results indicate that Bax, PARP, pro-caspase-3, and Bcl-2 were dose-dependently regulated by curcumin, with seemingly higher Bax/Bcl-2 ratios in DMS53. In addition, autophagic proteins, p-AKT, p62, and LC3B, were dose-dependently regulated by curcumin. ROS inhibition by diphenyleneiodonium reduced the induction of apoptosis and autophagy generated by curcumin. Taken together, it is suggested that curcumin induces apoptosis and autophagy via ROS generation, leading to cell death, with minor differences between human lung cancer cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.166-166
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• 2012

We examined the distribution of Co ions of ferromagnetic n-type Zn(1-x)Co(x)O semiconducting films with the Co concentrations of 0.03~0.07 using x-ray absorption fine structure (XAFS) measurements at the Co and Zn K edges. Extended XAFS (EXAFS) revealed that Co ions mainly occupied the zinc sites of the films. X-ray absorption near edge structure (XANES) spectra demonstrated that the pre-edge peak of the Co K edge was substantially affected by the second neighboring Co ions at the zinc sites due to hybridizing of the Co 4p conduction electrons with the Co 3d bounded electrons. From XANES and EXAFS analysis using ab initio calculations, we found that Co ions uniformly occupied the zinc sites of the Zn (0.93) Co (0.07)O film, whereas the Co ions of the Zn (0.97) Co (0.03)O and Zn (0.95) Co (0.05)O films were substituted at localized zinc sites. The ferromagnetic properties of the Zn (0.93) Co(0.07)O film could be induced by direct interaction between the magnetic dipoles of the Co ions with a mean distance of 4.3 A or by Co 4p electron mediation.

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.595-599
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• 2004

We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.112-112
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• 2003

최근 자성반도체(diluted magnetic semiconductor; DMS)를 이용한 소자 개발이 가긍해짐에 따라 국내외에서 활발한 연구가 이루어지고 있다. 본 연구실에서는 GaN-단일전구체를 이용하여 상온에서 자기적 특성을 나타내는 p-type GaMnN를 성장시켰다 극한 환경에서의 자성반도체 재료의 물성 변화를 알아보기 위해, 본 연구에서는 세계 최초로 중성자 빔의 조사에 따른 자성반도체의 구조적, 자기적 특성 및 열처리에 따른 특성 변화를 관찰 및 분석하였다. Molecular beam epitaxy(MBE)를 이용하여 Mn cell 온도가 각각 77$0^{\circ}C$, 94$0^{\circ}C$인 GaMnN 박막을 성장시켰다. 성장된 박막 시편에 한국원자력연구소 하나로 HTS공에서 중성자 빔을 각각 20min(4.17$\times$$10^{16}$n/$\textrm{cm}^2$), 24hour(3.0$\times$$10^{18}$n/$\textrm{cm}^2$)씩 조사하였다 중성자 빔을 조사한 시편은 진공분위기 하에서 100$0^{\circ}C$, 30초간 열처리하였다.(rapid thermal annealing;RTA, 승온속도: 8$^{\circ}C$/sec) 중성자 빔을 조사한 GaMnN 박막의 구조적인 특성은 X-ray diffraction(XRD) 측정을 통해 관찰하였고, 박막의 자기적 특성은 superconducting quantum interference device(SQUID)를 통해 측정하였다.