• Nuclear Engineering and Technology
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• 제25권1호
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• pp.71-79
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• 1993

소둔시편 및 소둔 후 냉간가공한 하프늄시편에 대하여 양전자수명을 조사하였다. 소둔시편에서의 양전자수명은 187$\pm$3.7 psec인 반면, 소둔 후 냉간가공한 시편에서 격자결함에 포획된 양전자의 수명은 217$\pm$4.2 psec로 측정되었다. 양전자소멸측정 및 미세경도측정 방법을 이용하여 등시소둔에 의한 냉간가공시편의 회복 및 재결정 거동을 조사하였다. 재결정단계에서는 양전자소멸측정 과 미세경도측정값이 유사한 경향을 나타냈으나, 회복단계에서는 양전자소멸측정값이 매우 현저하게 변화하는 반면, 미세경도값은 거의 변화하지 않았다. 하프늄의 회복단계는 623 K부터 시작되며 재결정온도는 1023 K정도로 측정되었다.

• 한국재료학회지
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• 제6권7호
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• pp.733-741
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• 1996

본 연구에서는 MeV Si 자기 이온주업을 실시하여 주업원자와 모재 원자와의 화학적 영향이 배제된 결함 형성 거동을 관찰하였다. 자기 이온주업을 위하여 Tandem Accelerator가 사용되었고 1~3 MeV의 에너지 범위의 이온주입이 실시되었다. MeV 이온주입된 시편의 격자결함은 표면으로부터 고립된 $R_p$ 근처에 집중된 것이 관찰되었다. 주입에너지 변화에 따른 격자결함 생성 거동을 관찰하기 위하여 조사량을 $1{\times}10^{15}/cm^2$으로 고정하고 주입에너지를 1~3 MeV로 증가하였다. RBS 분석 결과 격자결함의 형성층 깊이는 에너지 증가에 따라 증가하였고 표면층에는 에너지 증가시 더욱 좋은 결정성을 유지하였다. 또한 주입에너지가 일정한 경우 조사량 증가시 $R_p$ 부근에 집중된 결함층의 농도는 증가하였으나 표면부근의 결함농도는 임계조사량 이상에서 포화되는 것이 관찰되었다. XTEM 분석 결과는 RBS의 결과와 잘 일치하였다. XTEM 관찰 결과 이온주업 상태의 결함층은 dark band의 형태로 관찰되었고 열처리시 이차결함은 이곳으로부터 생성되었다. 2MeV $Si^+$ 자기 이온주입시 이차결함이 형성되는 임계조사량은 $3{\times}10^{14}{\sim}5{\times}10^{14}/cm^2$ 사이로 관찰되었다. 열처리시 dark band의 하단부의 위치는 변화하지 않고 상단부만이 제거되었다. 실험을 통하여 얻은 결과들은 Monte-Carlo technique을 이용한 TRIM-code를 사용하여 해석하였다. SIMS 분석을 통하여 이차결함은 모재내에 존재하는 oxygen 불순물을 gettering함을 관찰하였다.

• 한국결정성장학회지
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• 제12권6호
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• pp.299-303
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• 2002

The relationship of crystallinity between defects distribution with (100) ZnTe/GaAs using HWE growth was investigated by four crystal rocking curve (FCRC) and transmission electron microscopy (TEM). The thickness dependence of crystal quality in ZnTe epilayer was evaluated. The FWHM value shows a strong dependence on ZnTe epilayer thickness. For the films thinner than 6 ${\mu}{\textrm}{m}$, the FWHM value decreases very steeply as the thickness increases. For the films thicker than 6 ${\mu}{\textrm}{m}$, it becomes an almost constant value. At the thickness of 12 $\mu\textrm{m}$ with the smallest value of 66 arcsec. which is the best value so far reported on ZnTe epilayers was obtained. Investigation into the nature and behavior of dislocations with film thickness in (100) ZnTe/(100)GaAs heterostructures grown by Hot Wall Epitaxy (HWE). This film defects range from interface to 0.7 ${\mu}{\textrm}{m}$ thickness was high density, due to the large lattice mismatch and thermal expansion coefficients. The thickness of 0.7~1.8 ${\mu}{\textrm}{m}$ was exists low defect density. In the thicker range than 1.8 ${\mu}{\textrm}{m}$ thickness was measured hardly defects.

• 한국전기전자재료학회논문지
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• 제16권11호
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• pp.969-974
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• 2003

HgGa$_2$S$_4$ single crystals were grown by the chemical transport reaction method. The HgGa$_2$S$_4$ single crystal crystallized into a defect chalcopyrite structure (I 4). The lattice constants of the single crystal were found to be a = 5.635 $\AA$ and c = 10.473 $\AA$. The direct and indirect optical energy gaps were found to be 2.84eV and 2.78eV, respectively. Photoluminescence peaks of HgGa$_2$S$_4$ single crystal were observed at 2.37 eV, 2.18 eV, and 1.81 eV. In the single crystal, the donor level of 0.25 eV, the acceptor levels of 0.97 eV and 0.41 eV were obtained by TSC, PICTS, and absorption measurements. The photoluminescence peaks were analyzed to relate to the indirect conduction band, the donor level, and the acceptor levels.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집
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• pp.47-52
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• 2004

$HgGa_2S_4$ single crystals were grown by the chemical transport reaction method. The $HgGa_2S_4$ single crystal crystallized into a defect chalcopyrite structure $(I\bar{4})$. The lattice constants of the single crystal were found to be a=5.635 ${\AA}$ and c=10.473 ${\AA}$. The direct and indirect optical energy gaps were found to be 2.84 eV and 2.78 eV, respectively. Photoluminescence peaks of $HgGa_2S_4$ single crystal were observed at 2.37 eV, 2.18 eV, and 1.81 eV. In the single crystal, the donor level of 0.25 eV, the acceptor levels of 0.97 eV and 0.41 eV were obtained by TSC, PICTS, and absorption measurements. The photoluminescence peaks were analyzed to relate to the indirect conduction band, the donor level, and the acceptor levels.

• 에너지공학
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• 제13권4호
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• pp.259-266
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• 2004

세라믹핵연료의 비열기구는 격자 진동 비열, 팽창 비열, 전도전자 및 결함비열 그리고 과잉비열로 구성된다. 비열을 표현하는 모델은 정압비열 항과 팽창비열 항 그리고 결함비열 항으로 구성된다. 본 연구에서는 세라믹 핵연료의 실험자료 또는 발표된 자료들을 종합 분석하였으며, 가장 적합한 모델을 추천하였다. $UO_2$, (U, Pu)혼합핵연료 및 사용후 핵연료의 비열 자료들이 분석되었다. 사용 후 핵연료의 경우 모의 핵연료의 비열로 대신하였다.

• Bulletin of the Korean Chemical Society
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• 제13권2호
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• pp.127-131
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• 1992

Changes in network structures of ${\alpha}-Nb_2O_5$ in the X MgO+(1-X) ${\alpha}-Nb_2O_5$ solid solutions occurring as the MgO doping level (X) was varied were investigated by means of infrared spectroscopy and X-ray analysis. X-ray diffraction revealed that all the synthesized specimens have the monoclinic structure. The FT-IR spectroscopy showed that the system investigated forms the solid solutions in which $Mg^{2+}$ ions occupy the octahedral sites in parent crystal lattice. Electrical conductivities were measured as a function of temperature from 600 to $1050{\circ}$ and $P_{O2}$ form $1{\times}10^{-5}$ to $2{\times}10^{-1}$ atm. The defect structure and conduction mechanism were deduced from the results. The $1}n$ value in ${\alpha}{\propto}{P_{O2}^{1}n}}$ is found to be -1/4 with single possible defect model. From the activation energy ($E{\alpha}$ = 1.67-1.73 eV) and the1/n value, electronic conduction mechanism is suggested with a doubly charged oxygen vacancy.

• Advances in materials Research
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• 제13권1호
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• pp.55-62
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• 2024

Cu-based sulfides have recently emerged as promising thermoelectric (TE) materials due to their low cost, non-toxicity, and abundance. In this research, point defect structure of Cu_2-xZnSnS₄ (x=0.1, 0.2, 0.3) samples were synthesized by the mechanical alloying method. Mixed powders of Cu, Zn, Sn and S were milled using high energy ball milling at a rotation speed of 300 rpm in Ar atmosphere. The milled Cu_2-xZnSnS₄ powders were heat-treated at 723 K for 24 h, and subsequently consolidated using spark plasma sintering (SPS) under an applied pressure of 60 MPa for 15 min. The thermal conductivity of the sintered Cu_2-xZnSnS₄ samples was evaluated. A well-defined Cu_2-xZnSnS₄ powders were successfully formed after milling for 16 h, with the particle sizes mostly distributed in the range of 60-100 nm. The lattice constants of aand cdecreased with increasing composition value x. The thermal conductivity of sintered x=0.1 sample exhibited the lowest value and attained 0.93 W/m K at 673 K.

• 한국세라믹학회지
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• 제29권4호
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• pp.265-272
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• 1992

Role of CaO in the sintering of 12Ce-TZP ceramics was studied. The addition of small amounts of CaO increase the densification rate of 12Ce-TZP by altering lattice defect structure and the diffusion coefficient of the rate controlling species, namely cerium and zirconium cations. CaO also inhibits grain growth during sintering and allows the sintering process to proceed to theoretical density by maintaining a high diffusion flux of vacancies from the pores to the grain boundaries. The inhibition of grain growth is accomplished by the segregation of solute at the grain boundaries, causing a decrease in the grain boundary mobility. The segregation of calcium was revealed by AES study.

• 전기학회논문지P
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• 제51권3호
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• pp.137-141
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• 2002

CdS and $CdS:Co^{2+}$ single crystals were grown by CTR method using iodine as transport material. The grown single crystals have defect chalcopyrite structure with direct band gap. The optical energy band gap was decreased according to add of Co-impurity. We can observed the Co-impurity optical absorption peaks assigned to the $Co^{2+}$ ion sited at the $T_d$ symmetry lattice and we consider that they were attributed to the electron transitions between energy levels of ions.