• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.191.2-191.2
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• 2015

Details of carrier dynamics in self-assembled quantum dots (QDs) with a particular attention to nonradiative processes are not only interesting for fundamental physics, but it is also relevant to performance of optoelectronic devices and the exploitation of nanocrystals in practical applications. In general, the possible processes in such systems can be considered as radiative relaxation, carrier transfer between dots of different dimensions, Auger nonradiactive scattering, thermal escape from the dot, and trapping in surface and/or defects states. Authors of recent studies have proposed a mechanism for the carrier dynamics of time-resolved photoluminescence CdTe (a type II-VI QDs) systems. This mechanism involves the activation of phonons mediated by electron-phonon interactions. Confinement of both electrons and holes is strongly dependent on the thermal escape process, which can include multi-longitudinal optical phonon absorption resulting from carriers trapped in QD surface defects. Furthermore, the discrete quantized energies in the QD density of states (1S, 2S, 1P, etc.) arise mainly from ${\delta}$-functions in the QDs, which are related to different orbitals. Multiple discrete transitions between well separated energy states may play a critical role in carrier dynamics at low temperature when the thermal escape processes is not available. The decay time in QD structures slightly increases with temperature due to the redistribution of the QDs into discrete levels. Among II-VI QDs, wide-gap CdZnTe QD structures characterized by large excitonic binding energies are of great interest because of their potential use in optoelectronic devices that operate in the green spectral range. Furthermore, CdZnTe layers have emerged as excellent candidates for possible fabrication of ferroelectric non-volatile flash memory. In this study, we investigated the optical properties of CdZnTe/ZnTe QDs on Si substrate grown using molecular beam epitaxy. Time-resolved and temperature-dependent PL measurements were carried out in order to investigate the temperature-dependent carrier dynamics and the activation energy of CdZnTe/ZnTe QDs on Si substrate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.343-344
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• 2012

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states. [1-3] We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• 우주기술과 응용
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• 제3권4호
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• pp.333-341
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• 2023

본 연구는 국내 100 MeV 양성자가속기와 우주부품시험센터 우주전문시험시설기반을 활용하여 우주부품의 우주 방사선환경 시험검증 기술을 개발하고자 한다. 우주개발의 진전에 따라 고도화된 위성의 임무는 위성의 핵심부품인 메모리 등에 고집적 회로를 필수적으로 사용하고, 태양전지, 광학센서 및 opto-electronics 등 부수 장치에 반도체 소자의 활용이 증가하고 있다. 특히, 전자부품을 우주에 적용하기 위해서는 우주환경 시험을 반드시 거쳐야 하며, 그 중 가장 중요한 것이 고 에너지 방사선환경에서의 우주부품시험이다. 따라서 이에 필요한 우주 방사선 환경 구현 시설을 갖추어 체계적인 시험절차를 수립할 필요가 있다. 한국산업기술시험원 우주부품시험센터는 메모리 부품에 대한 방사선 시험 장치를 제작하고 이를 이용한 메모리 방사선 영향 평가 시험을 수행하였다. 경주양성자가속기에서 100 MeV 양성자를 활용하여 한국에서 활용가능한 수준의 방사선 시험을 진행하였다. 이러한 시험을 통해 메모리 반도체에서 나타나는 single event upset을 관찰할 수 있었다. 향후 해당 시험을 체계화하여 우주산업화에 기반을 마련하고자 한다.

• 한국재료학회지
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• 제34권8호
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• pp.400-407
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• 2024

The reversible metal electrodeposition (RME) process is used to prepare electrochromic mirrors with reflective-transparent optical states, by depositing metal particles on transparent conductive substrates. These RME based devices can be used in smart windows to regulate indoor temperatures and light levels, serving dual purposes as lighting elements. Commercialization efforts are focused on achieving large-scale production, long-term durability, and a memory effect that maintains coloration without applied voltage. Enhancing durability has received particular attention, leading to the development of electrochromic mirrors that employ gel electrolytes, which are expected to reduce electrolyte leakage and improve mechanical stability compared to traditional liquid electrolyte devices. The gel electrolytes offer the additional advantage of various colors, by controlling the metal particle size and enabling smoother, denser formations. In this study, we investigated improving the durability of RME devices by adding polyvinyl butyral (PVB) to the liquid electrolyte and optimizing the concentration of PVB. Incorporating 10 % PVB resulted in excellent interfacial properties and superior electrochromic stability, with 92.6 % retention after 1,000 cycles.

• 한국정보통신학회논문지
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• 제16권5호
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• pp.999-1008
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• 2012

ISB(Intelligent Silicon Bead)는 기존 CMOS 칩과 달리 CMOS SoC의 전원을 포함한 외부와의 인터페이스(interface)를 모두 빛을 이용하여 칩의 초소형화 및 단가를 낮추고 광통신, 메모리 기능을 탑재한 신개념 바이오 실험용 칩이다. 본 논문에서는 외부리더기로부터 비드칩에 인가된 하나의 광신호를 통해 전력과 신호를 동시에 전달하기 위한 저전력, 저면적특성의 광수신단 설계와 입력프로토콜에 대해서 소개하고 이를 시뮬레이션 및 측정을 통해 검증한다. 또한 칩의 ID를 기록/저장하기 위한 저전력 PROM을 설계하여 광신호 입력에 따른 출력 결과 값을 얻는데 성공한다. 본 연구를 통하여 기존 RFID에서 발생한 칩면적 소형화의 한계와 높은 단가 등의 문제점을 해결하여 새로운 유형의 바이오용 칩 개발을 기대할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.734-737
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• 2004

The metal-ferroelectric-semiconductor (MFS) structure is widely studied for nondestructive readout (NDRO) memory devices, but conventional MFS structure has a critical problem. It is difficult to obtain ferroelectric films like PZT on Si substrate without interdiffusion of impurities such as Pb, Ti and other elements. In order to solve these problems, the metal-ferroelectric-insulator-semiconductor (MFIS) structure has been proposed with a buffer layer of high dielectric constant such as MgO, $Y_2O_3$, and $CeO_2$. In this study, the etching characteristics (etch rate, selectivity) of MgO thin films were etched using $Cl_2/Ar$ plasma. The maximum etch rate of 85 nm/min for MgO thin films was obtained at $Cl_2$(30%)/Ar(70%) gas mixing ratio. Also, the etch rate was measured by varying the etching parameters such as ICP rf power, dc-bias voltage, and chamber pressure. Plasma diagnostics was performed by Langmuir probe (LP) and optical emission spectroscopy (OES).

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.25-28
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• 2003

Carbon nanotubes(CNTs), since their first discovery, have been considered as new promising materials in various fields of applications including field emission displays, memory devices, electrodes, NEMS constituents, hydrogen storages and reinforcements in composites due to their extra-ordinary properties. The carbon nanotube reinforced nanocomposites have attracted attention owing to their outstanding mechanical and electrical properties and are expected to overcome the limit of conventional materials. Various application areas are possible for carbon nanotube reinforced nanocomposites through the functionalization of carbon nanotubes. Carbon nanotube reinforced polymer matrix nanocomposites have been fabricated by liquid phase process including surface functionalization and dispersion of CNTs within organic solvent. In case of carbon nanotube reinforced polymer matrix nanocomposites, the mechanical strength and electrical conducting can be improved by more than an order of magnitude. The carbon nanotube reinforced polymer matrix nanocomposites can be applied to high strength polymers, conductive polymers, optical limiters and EMI materials. In spite of successful development of carbon nanotube reinforced polymer matrix nanocomposites, the researches on carbon nanotube reinforced inorganic matrix nanocomposites show limitations due to a difficulty in homogeneous distribution of carbon nanotubes within inorganic matrix. Therefore, the enhancement of carbon nanotube reinforced inorganic nanocomposites is under investigation to maximize the excellent properties of carbon nanotubes. To overcome the current limitations, novel processes, including intensive milling process, sol-gel process, in-situ process and spark plasma sintering of nanocomposite powders are being investigated. In this presentation, current research status on carbon nanotube reinforced nanocomposites with various matrices are reviewed.

• 한국재료학회지
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• 제30권2호
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• pp.99-104
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• 2020

Recent discoveries of ferroelectric properties in ultrathin doped hafnium oxide (HfO₂) have led to the expectation that HfO₂ could overcome the shortcomings of perovskite materials and be applied to electron devices such as Fe-Random access memory (RAM), ferroelectric tunnel junction (FTJ) and negative capacitance field effect transistor (NC-FET) device. As research on hafnium oxide ferroelectrics accelerates, several models to analyze the polarization switching characteristics of hafnium oxide ferroelectrics have been proposed from the domain or energy point of view. However, there is still a lack of in-depth consideration of models that can fully express the polarization switching properties of ferroelectrics. In this paper, a Zr-doped HfO₂ thin film based metal-ferroelectric-metal (MFM) capacitor was implemented and the polarization switching dynamics, along with the ferroelectric characteristics, of the device were analyzed. In addition, a study was conducted to propose an applicable model of HfO₂-based MFM capacitors by applying various ferroelectric switching characteristics models.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.132-132
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• 2011

For the programming volume of PRAM, Ge2Sb2Te5(GST) thin films have been dominantly used and prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD). Among these methods, ALD is particularly considered as the most promising technique for the integration of PRAM because the ALD offers a superior conformality to PVD and CVD methods and a digital thickness control precisely to the atomic level since the film is deposited one atomic layer at a time. Meanwhile, although the IST has been already known as an optical data storage material, recently, it is known that the IST benefits multistate switching behavior, meaning that the IST-PRAM can be used for mutli-level coding, which is quite different and unique performance compared with the GST-PRAM. Therefore, it is necessary to investigate a possibility of the IST materials for the application of PRAM. So far there are many attempts to deposit the IST with MOCVD and PVD. However, it has not been reported that the IST can be deposited with the ALD method since the ALD reaction mechanism of metal organic precursors and the deposition parameters related with the ALD window are rarely known. Therefore, the main aim of this work is to demonstrate the ALD process for IST films with various precursors and the conformal filling of a nano size programming volume structure with the ALD?IST film for the integration. InSbTe (IST) thin films were deposited by ALD method with different precursors and deposition parameters and demonstrated conformal filling of the nano size programmable volume of cell structure for the integration of phase change random access memory (PRAM). The deposition rate and incubation time are 1.98 A/cycle and 25 cycle, respectively. The complete filling of nano size volume will be useful to fabricate the bottom contact type PRAM.

• 한국재료학회지
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• 제11권3호
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• pp.197-202
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• 2001

교류구동형 플라즈마 표시소자의 보호막으로 사용되는 MgO의 특성향상을 위하여 기존의 MgO에 양이온이 등전적으로 치환될 수 있는 ZnO를 소량 첨가하여 고주파 마그네트론 스퍼터링 방법으로 $Mg_{1-x}$Z $n_{x}$O박막을 성장시키고 박막의 전기적, 광학적 특성을 조사하였다. ZnO농도가 0.5 at%, 1at%인 $Mg_{1-x}$Z $n_{x}$O 박막을 보호막으로 갖는 PDP 테스트 판넬을 제작하고 ZnO의 첨가가 소자의 방전전압과 메모리 이득에 미치는 영향을 살펴보았다. ZnO농도가 0at%, 0.5 at%, 1at%인 $Mg_{1-x}$Z $n_{x}$O 박막의 광투과율은 ZnO 첨가에 따라 변화를 보이지 않으나 유전상수는 다소 증가하는 경향을 보였다. ZnO의 농도가 0.5 at%인 $Mg_{1-x}$Z $n_{x}$O 박막을 보호막으로 갖는 PDP 소자의 방전개시전압과 방전유지 전압이 MgO 박막을 보호막으로 갖는 소자에 비해 20V까지 낮아졌고, 결과적으로 메모리계수는 다소 증가하였다. ZnO농도가 0.5 at%, 1at%인 $Mg_{1-x}$Z $n_{x}$O 박막을 보호막으로 갖는 소자에서 ZHO의 첨가에 비례하여 방전세기 (플라즈마 밀도)가 증가하였다.도)가 증가하였다.도)가 증가하였다.