• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2002년도 춘계학술대회논문집
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• pp.167-171
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• 2002

We have investigated the optical properties of Te-doped ZnSSe:Te epitaxial layers grown on (100) GaAs substrates by molecular beam epitaxy. The Te-doped ternary specimen shows strong blue or green emission (at 300k) which is assigned to Te$_{1}$ or Te$_{n}$( n$\geq$2) cluster bound exciton. Bright green and blue light-emitting diodes (LEDs) have been developed using ZnSSe:Te system as an active layer. The green LEDs exhibit a fairly long device lifetime (>2000 h) when operated at 3 A/cm$^{2}$ under CW condition at room temperature. It is confirmed that the Te-doping induced "crystal-hardening effect" plays a significant role in both efficient and strong suppression of the optical device degradation.gradation.

• 한국세라믹학회지
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• 제45권5호
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• pp.276-279
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• 2008

In this research, properties of $N_2$-doped $Sb_2Te_3$ thin film were evaluated using 4-point probe, XRD and AFM. $Sb_2Te_3$ material has faster crystallization rate than $Ge_2Sb_2Te_5$, but sheet resistance difference between amorphous and crystallization state is very low. This low sheet resistance difference decreases sensing margin in reading operation at PRAM device operation. Therefore, in order to overcome this weak point, $N_2$ gas was doped on $Sb_2Te_3$ thin film. Sheet resistance difference between amorphous and crystallized state of $N_2$-doped $Sb_2Te_3$ thin film showed about $10^4$ times higher than Un-doped $Sb_2Te_3$ thin film because of the grain boundary scattering.

• 한국표면공학회지
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• 제49권1호
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• pp.40-45
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• 2016

Recently, $Bi_2Te_3$-based alloys are the best thermoelectric materials near to room temperature, so it has been researched to achieve increased figure of merit(ZT). Ternary compounds such as Bi-Te-Se and Bi-Sb-Te have higher thermoelectric property than binary compound Bi-Te and Sb-Te, respectively. Compared to DC plating method, pulsed electrodeposition is able to control parameters including average current density, and on/off pulse time etc. Thereby the morphology and properties of the films can be improved. In this study, we electrodeposited n-type ternary Cu-doped $Bi_2(Te-Se)_3$ thin film by modified pulse technique at room temperature. To further enhance thermoelectric properties of $Bi_2(Te-Se)_3$ thin film, we optimized Cu doping concentration in $Bi_2(Te-Se)_3$ thin film and correlated it to electrical and thermoelectric properties. Thus, the crystal, electrical, and thermoelectric properties of electrodeposited $Bi_2(Te-Se)_3$ thin film were characterized the XRD, SEM, EDS, Seebeck measurement, and Hall effect measurement, respectively. As a result, the thermoelectric properties of Cu-doped $Bi_2(Te-Se)_3$ thin films were observed that the Seebeck coefficient is $-101.2{\mu}V/K$ and the power factor is $1412.6{\mu}W/mK^2$ at 10 mg of Cu weight. The power factor of Cu-doped $Bi_2(Te-Se)_3$ thin film is 1.4 times higher than undoped $Bi_2(Te-Se)_3$ thin film.

• Current Photovoltaic Research
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• 제3권1호
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• pp.10-15
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• 2015

Cu doping by copper or $Cu_2Te$ materials enhances p+ formation in CdTe near the back contact interface, allowing better formation of ohmic contact. However, the Cu in CdTe junction is also considered as a principal component of CdTe cell degradation. In this paper, Na-doped ZnTe layer was employed as a back contact material to improve the stability of CdTe solar cells. As a process variable, post $CdCl_2$ treatment of CdS/CdTe film was conducted before or after depositing ZnTe:Na on CdTe. The change of the photovoltaic properties of CdTe cells were investigated with aging time. Low-temperature photoluminescence analysis was conducted to describe the degradation mechanism. The result showed that the CdTe solar cells with better stability compare to Cu contact were achieved using an optimized ZnTe:Na back contact.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.376-381
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• 2019

In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.300-300
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• 2012

프로그래머블 스위치는 프로그래머블 로직 디바이스 내에서 사용자의 프로그래밍에 따라 로직 블록과 배선을 연결하거나 차단하는 기능을 수행하는 전자소자이다. 기존의 프로그래머블 스위치는 상변화 특성을 보이는 칼코겐화물을 이용하는데, 상변화 재료만을 이용하는 스위치는 전기신호 누설의 문제점을 가지고 있다. 이러한 문제점을 해결하기 위하여 본 연구에서는 프로그래머블 스위치의 활성물질로서 상변화 재료 및 문턱(threshold) 스위칭 특성을 보이는 칼코겐화물을 포함하는 다층구조를 제안하고, 다층구조에 적용 가능한 칼코겐화물 합금 특성을 보고한다. RF magnetron sputtering 방식을 이용하여 doped GeSbTe 박막을 증착하고 온도에 따른 면저항 및 표면 형상 변화를 관찰하였다. Doped GeSbTe는 기존의 GeSbTe 상변화 재료와는 뚜렷하게 구분되는 면 저항 및 표면 형상 변화를 나타내었다. 이러한 결과로부터 doped GeSbTe 합금 박막은 다층구조 프로그래머블 스위치의 활성물질로 사용이 가능하다는 사실을 확인할 수 있었다.

• 태양에너지
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• 제17권3호
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• pp.51-57
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• 1997

열벽 증착(hot-wall evaporation)방법으로 Cu를 첨가한 ZnTe박막을 성장하였다. doping을 하지 않은 ZnTe박막의 전기 전도형은 p-형으로 전기 전도도는 $10^{-6}({\Omega}{\cdot}cm)^{-1}$을 정도로 매우 낮았다. 첨가한 Cu의 양에 따라 전기 전도도는 $10^2({\Omega}{\cdot}cm)^{-1}$까지 증가하였으나 이동도는 크게 변하재 않았다. Cu를 매우 많이 첨가한 경우는 금속과 같은 전기 전도도를 관찰하였다.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.88-93
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• 2024

To evaluate the possibility as a multi-level memory medium for the Ge₂Sb₂Te₅/TiN/W-doped Ge₂Sb₂Te₅ cell structure, the crystallization rate and stabilization characteristics according to voltage (V)- and current (I)- pulse sweeping were investigated. In the cell structures prepared by a magnetron sputtering system on a p-type Si (100) substrate, the Ge₂Sb₂Te₅ and W-doped Ge₂Sb₂Te₅ thin films were separated by a barrier metal, TiN, and the individual thicknesses were varied, but the total thickness was fixed at 200 nm. All cell structures exhibited relatively stable multi-level states of high-middle-low resistance (HR-MR-LR), which guarantee the reliability of the multilevel phase-change random access memory (PRAM). The amorphousto-multilevel crystallization rate was evaluated from a graph of resistance (R) vs. pulse duration (T) obtained by the nanoscaled pulse sweeping at a fixed applied voltage (12 V). For all structures, the phase-change rates of HR→MR and MR→LR were estimated to be approximately t<20 ns and t<40 ns, respectively, and the states were relatively stable. We believe that the doublestack structure of an appropriate Ge-Sb-Te film separated by barrier metal (TiN) can be optimized for high-speed and stable multilevel PRAM.

• 한국재료학회지
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• 제9권2호
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• pp.173-180
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• 1999

Thermally evaporated ZnTe films were investigated as a back contact material for CdS/CdTe solar cells. Two deposition methods, coevaporation and double-layer methods, were used for Cu doping in ZnTe films. ZnTe layers (0.2$\mu\textrm{m}$ thick) were deposited either on glass or on CdS/CdTe substrates without intentional heating of the substrates. Post-deposition annealing was performed at 200,300 and $400^{\circ}C$ for 3,6 and 9 minutes, respectively. Band gap of 2.2eV was measured for both undoped and doped films and a slight change in the shape of absorption spectra was observed in Cu-doped samples after annealing at $400^{\circ}C$. The resistivity of as-deposited ZnTe decreased from 10\ulcorner~10\ulcornerΩcm down to 10\ulcornerΩcm as Cu concentration increased from 0 to 14 at.%. There was not a noticeable change in less of annealing temperature up to $300^{\circ}C$ whereas films annealed at $400^{\circ}C$ revealed hexagonal (101) orientations as well. Some of Cu-doped ZnTe revealed x-ray diffraction (XRD) peaks related with Cu\ulcornerTe(x=1.75~2). Grain growth was observed from about 20nm in as-deposited films to 50nm after annealing at $400^{\circ}C$ by scanning electron microscopy (SEM). Cu distribution in ZnTe films was not uniform according to Auger electron spectroscopy (AES) measurements.

• 한국전기전자재료학회논문지
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• 제30권3호
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• pp.133-138
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• 2017

We evaluated the structural, electrical and optical properties of tungsten (W)-doped $Ge_8Sb_2Te_{11}$ thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve thermal stability. 200 mm thick $Ge_8Sb_2Te_{11}$ and W-doped $Ge_8Sb_2Te_{11}$ films were deposited on p-type Si (100) and glass substrates using a magnetron co-sputtering system at room temperature. The fabricated films were annealed in a furnace in the $0{\sim}400^{\circ}C$ temperature range. The structural properties were analyzed using X-ray diffraction (X'pert PRO, Phillips). The results showed increased crystallization temperature ($T_c$) leading to thermal stability in the amorphous state. The optical properties were analyzed using an UV-Vis-IR spectrophotometer (Shimadzu, U-3501, range : 300~3,000 nm). The results showed an increase in the crystalline material optical energy band gap ($E_{op}$) and an increase in the $E_{op}$ difference (${\Delta}E_{op}$). This is a good effect to reduce memory device noise. The electrical properties were analyzed using a 4-point probe (CNT-series). This showed increased sheet resistance ($R_s$), which reduces programming current in the memory device.