• 한국생산제조학회지
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• 제19권3호
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• pp.388-393
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• 2010

In recent years the research has been focused on the preparation of special glasses, i.e., chalcogenide and heavy metal oxide ones that can transmit optical radiation above 2 um and also other optical parameters exceed those of silica based glasses. The attention in this paper is focused on chalcogenide glasses, on preparation of high quality base glass, for an application in infrared optical product design and manufacture. The amorphous materials of As-Se and Ge-As-Se chalcogenides were prepared by a standard melt-quenching technique. The compositions were mesaured by ICP-AES and EPMA, and structural and thermal properties were studied through various annealing processes. Several anomalies of glass transition and crystallization were observed in the DSC/DTA/TG results of the chalcogenide glass.

• Bulletin of the Korean Chemical Society
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• 제27권3호
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• pp.363-367
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• 2006

The structure-property relations of ternary copper chalcogenides, $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ are examined. The density of states, band dispersions, and Fermi surfaces of these compounds are investigated to verify the reason of the metal-insulator transitions by extended Huckel tight-binding band calculations. The origin of the metalinsulator transitions of non-stoichiometric $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ is thought to be the electronic instability induced by their Fermi surface nesting.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.210-213
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• 2004

The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. Memory switching in chalcogenides is mostly a thermal process, which involves phase transformation from amorphous to crystalline state. The nonvolatile memory cells are composed of a simple sandwich (metal/chalcogenide/metal). It was formed that the threshold voltage depends on thickness, electrode distance, annealing time and temperature, respectively.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.

• 청정기술
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• 제29권3호
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• pp.178-184
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• 2023

전이금속 칼코젠화물은 소듐 이차전지의 음극재로서 높은 이론 용량을 가지나 충·방전 과정에서 큰 부피 팽창으로 인해 짧은 수명 특성을 보이며, 낮은 전기전도도로 인해 출력 특성을 저하시킨다는 문제가 있다. 이를 해결하기 위해, 본 연구에서는 분무열분해와 후 열처리 공정을 통해 다공성의 CNT ball과 (Ni,Co)Se₂ 나노결정이 복합된 구조체를 합성하였으며, 이를 소듐 이차전지의 음극에 적용시켜 전기화학적 특성을 평가하였다. 합성된 소재는 분무열분해 동안 Polystyrene(PS) 나노비드의 분해로 인해 다공성 구조를 형성하여 충방전 과정에서 발생하는 부피팽창을 효과적으로 수용하였으며, CNT 소재와의 복합화를 통해 전기화학적 성능을 향상시킬 수 있었다. 이로 인해 다공성 구조의 (Ni,Co)Se₂-CNT 복합소재는 0.2 A g^-1의 전류밀도에서 698 mA h g^-1의 높은 초기 방전용량을 보였으며, 100 사이클 후 400 mA h g^-1의 방전용량을 유지함을 보였다.

• 한국분말재료학회지
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• 제30권5호
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• pp.387-393
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• 2023

Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni₃Co₆S₈-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni₃Co₆S₈@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni₃Co₆S₈@C-YS exhibited an impressive reversible capacity of 525.2 mA h g^-1 at a current density of 0.5 A g^-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni₃Co₆S₈ yolk shell nanopowder (Ni₃Co₆S₈-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni₃Co₆S₈@C-YS were attributed to the pitch-derived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.222.2-222.2
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• 2016

트랜지스터 응용 등에 관한 연구가 활발해 지면서 에너지 밴드갭이 0 eV에 가까운 그래핀 이외의 밴드 갭 조절이 가능한 MoS2 (molybdenum disulfide), BN (boron nitride), Bi2Te3 (bismuth telluride), WS2 (tungsten disulfide) 등과 같은 이차원 Transition Metal DiChalcogenides (TMDC) 물질이 반도체 물질로 각광받고 있다. 특히 MoS2의 경우 단결정 덩어리 상태에서는 약 1.3 eV의 밴드갭을 가지나 두께가 줄어들어 두 층일 경우에는 약 1.65 eV, 단일층이 되면 약 1.9 eV의 밴드갭을 가져 박막 층수에 따라 에너지 밴드갭 조절이 가능한 것으로 알려져있다. 하지만 두께 조절이 가능하면서 대면적, 고품질을 가지는 MoS2 박막 합성은 아직 제한적이라 할 수 있으며 새로운 방법 및 물질에 대한 연구가 지속적으로 이루어 지고 있다. 따라서 본 연구에서는 다양한 층수를 지니는 MoS2 합성을 위해 나노 두께의 MoS2 박막을 CF4 plasma 를 이용하여 layer etching 진행하고 CF4 plasma 100초 etching 진행한 2 layer 두께의 MoS2를 기준으로 H2S plasma를 이용하여 treatment 진행하였다. 물리적, 화학적 분석은 Raman spectroscopy, XPS(X-ray Photoelectron Spectroscopy), AFM (Atomic Force Microscopy) 등을 이용해 진행하였고 이를 통해 MoS2 layer 감소 및 damage recovery 등을 확인하였다.