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비정질 Ge<SUB>1 − x</SUB>Mn<SUB>x</SUB> 박막의 자기수송특성에 미치는 열처리 효과
김동휘(Dong Hwi Kim),이병철(Byeong Cheol Lee),찬티난안(Tran Thi Lan Anh),임영언(Young Eon Ihm),김도진(Dojin Kim),김효진(Hyojin Kim),유상수(Sang Soo Yu),백귀종(Kui Jong Baek),김창수(Chang Soo Kim) 한국자기학회 2009 韓國磁氣學會誌 Vol.19 No.4
Amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> semiconductor thin films grown by low temperature vapor deposition were annealed at various temperatures from 400 to 700 ℃ for 3 minutes in high vaccum chamber. The electrical and magnetotransport properties of as-grown and annealed samples have been studied. X-ray diffraction patterns analysis revealed that the samples still maintain amorphous state after annealling at 500 ℃ for 3 minutes and they were crystallized when annealing temperature increase to 600 ℃. Temperature dependence of resistivity measurement implied that as-grown and annealed Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> films have semiconductor characteristics, the increase of resistivity with annealling temperature was obseved. The 700 ℃-annealed sample exhibited negative magnetoresistance (MR) at low temperatures and the MR ratio was ~8.5% at 10 K. The asymmetry was present in all MR curves. The anomalous Hall Effect was also observed at 250 K.
비정질 Ge<SUB>1 − x</SUB>Mn<SUB>x</SUB> 박막의 전기적, 자기적 특성에 미치는 열처리 효과
이병철(Byeong Cheol Lee),김동휘(Dong Hwi Kim),찬티난안(Tran Thi Lan Anh),임영언(Young Eon Ihm),김도진(Dojin Kim),김효진(Hyojin Kim),유상수(Sang Soo Yu),백귀종(Kui Jong Baek),김창수(Chang Soo Kim) 한국자기학회 2009 韓國磁氣學會誌 Vol.19 No.3
Amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> semiconductor thin films grown by low temperature vapor deposition were annealed, and their electrical and magnetic properties have been studied. The amorphous thin films were 1,000~5,000 A thick. Amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> thin films were annealed at 300 ℃, 400 ℃, 500 ℃, 600 ℃ and 700 ℃ for 3 minutes in high vacuum chamber. X-ray diffraction analysis reveals that as-grown Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> semiconductor thin films are amorphous and are crystallized by annealing. Crystallization temperature of amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> semiconductor thin films varies with Mn concentration. Amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> thin films have p-type carriers and the carrier type is not changed during annealing, but the electrical resistivity increases with annealing temperature. Magnetization characteristics show that the as-grown amorphous Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> thin films are ferromagnetic and the Curie temperatures are around 130 K. Curie temperature and saturation magnetization of annealed Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> thin films increase with annealing temperature. Magnetization behavior and X-ray analysis implies that formation of ferromagnetic Ge3Mn5 phase causes the change of magnetic and electrical properties of annealed Ge<SUB>1 ? x</SUB>Mn<SUB>x</SUB> thin films.
이동석,김도진,김효진,Lee, Dongsuk,Kim, Dojin,Kim, Hyojin 한국재료학회 2015 한국재료학회지 Vol.25 No.5
$H_2S$ is a flammable toxic gas that can be produced in plants, mines, and industries and is especially fatal to human body. In this study, CuO nanowire structure with high porosity was fabricated by deposition of copper on highly porous singlewall carbon nanotube (SWCNT) template followed by oxidation. The SWCNT template was formed on alumina substrates by the arc-discharge method. The oxidation temperatures for Cu nanowires were varied from 400 to $800^{\circ}C$. The morphology and sensing properties of the CuO nanowire sensor were characterized by FESEM, Raman spectroscopy, XPS, XRD, and currentvoltage examination. The $H_2S$ gas sensing properties were carried out at different operating temperatures using dry air as the carrier gas. The CuO nanowire structure oxidized at $800^{\circ}C$ showed the highest response at the lowest operating temperature of $150^{\circ}C$. The optimum operating temperature was shifted to higher temperature to $300^{\circ}C$ as the oxidation temperature was lowered. The results were discussed based on the mechanisms of the reaction with ionosorbed oxygen and the CuS formation reaction on the surface.