• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.9-9
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• 2011

There has been strong demand for novel nonvolatile memory technology for low-cost, large-area, and low-power flexible electronics applications. Resistive memories based on metal oxide thin films have been extensively studied for application as next-generation nonvolatile memory devices. However, although the metal oxide-based resistive memories have several advantages, such as good scalability, low-power consumption, and fast switching speed, their application to large-area flexible substrates has been limited due to their material characteristics and necessity of a high-temperature fabrication process. As a promising nonvolatile memory technology for large-area flexible applications, we present a graphene oxide-based memory that can be easily fabricated using a room temperature spin-casting method on flexible substrates and has reliable memory performance in terms of retention and endurance. The microscopic origin of the bipolar resistive switching behaviour was elucidated and is attributed to rupture and formation of conducting filaments at the top amorphous interface layer formed between the graphene oxide film and the top Al metal electrode, via high-resolution transmission electron microscopy and in situ x-ray photoemission spectroscopy. This work provides an important step for developing understanding of the fundamental physics of bipolar resistive switching in graphene oxide films, for the application to future flexible electronics.

• 마이크로전자및패키징학회지
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• 제27권4호
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• pp.77-81
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• 2020

Resistive RAM (ReRAM)은 전이금속 산화물의 저항변화 특성을 이용하는 차세대 비휘발 메모리로 전이금속산화물 내의 산소공공의 재분포를 통한 저항변화 특성을 이용한다. 따라서 저항변화 특성을 위해 전이금속산화물 내에는 일정량 이상의 산소공공이 요구되며 이를 위해서는 박막 형성 공정에서 산화 수를 조절할 수 있는 공정이 필요하다. 본 연구에서는 직접패턴이 가능한 photochemical metal organic deposition (PMOD) 공정을 사용하여 UV 노출에 의해 photochemical metal organic precursor의 ligand가 분해되는 과정에서 전기장을 인가하여 박막내의 산화 수를 조절하는 실험을 진행하였다. Electric field assisted PMOD (EFAPMOD) 법을 이용하여 FeOx 박막의 산화 수 조절이 가능함을 x-ray photoelectron spectroscopy (XPS) 분석과 I-V 측정을 통하여 확인하였으며, EFAPMOD 공정 중 인가하는 전압의 크기를 조절하여 박막의 산화 수를 조절할 수 있음을 확인하였다. 따라서 EFAPMOD 공정 중 인가전압의 크기를 이용하여 저항변화 특성에 적합한 적정한 산화수를 가지는 금속산화물 박막을 얻고 그 저항변화 특성을 조정할 수 있음을 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.207.1-207.1
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• 2013

Tantalum oxide has been extensively investigated as one of the promising Resistive switching materials applicable to Resistive Dynamic Access Memories. Impedance spectroscopy offers simultaneous measurements of electrical and dielectric information, separation of electrical origins among bulk, grain boundaries, and interfaces, and the monitoring of electrical components. Such benefits have been combined with the resistive states of resistive switching devices which can be described in terms of equivalent circuits involving resistors, capacitors, and inductors, The current work employed pulsed laser deposition in order to prepare the oxygen-deficient tantalum oxide. The fabricated devices were controlled between highresistance and low-resistance states in controlled current compliance modes. The corresponding electrical phenomena were monitored both in the dc-based current-voltage characteristics and in the ac-based impedance spectroscopy. The origins of the electrical switching are discussed towards optimized ReRAM devices in terms of interfacial effects.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.28.2-28.2
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• 2011

Resistance random access memory (ReRAM) is a promising candidate for next-generation nonvolatile memory because of its advantageous qualities such as simple structure, superior scalability, fast switching speed, low-power operation, and nondestructive readout. We investigated the resistive switching behavior of tantalum oxide that has been widely used in dynamic random access memories (DRAM) in the present semiconductor industry. As a result, it possesses full compatibility with the entrenched complementary metal-oxide-semiconductor processes. According to previous studies, TiN is a good oxygen reservoir. The TiN top electrode possesses the specific properties to control and modulate oxygen ion reproductively, which results in excellent resistive switching characteristics. This study presents fully room temperature fabricated the TiN/$TaO_x$/Pt devices and their electrical properties for nonvolatile memory application. In addition, we investigated the TiN electrode dependence of the electrical properties in $TaO_x$ memory devices. The devices exhibited a low operation voltage of 0.6 V as well as good endurance up to $10^5$ cycles. Moreover, the benefits of high devise yield multilevel storage possibility make them promising in the next generation nonvolatile memory applications.

• Transactions on Electrical and Electronic Materials
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• 제11권6호
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• pp.243-248
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• 2010

The emergence of different and disparate materials together with the convergence of both the 'old' and 'emerging' technologies is paving the way for integration of heterogeneous technologies that are likely to extend the limitations of silicon technology beyond the roadmap envisaged for complementary metal-oxide semiconductor. Formulation of new information processing concepts based on novel aspects of nano-scale based materials is the catalyst for new nanoarchitectures driven by a different perspective in realization of novel logic devices. The memory technology has been the pace setter for silicon scaling and thus far has pave the way for new architectures. This paper provides an overview of the inevitability of heterogeneous integration of technologies that are in their infancy through initiatives of material physicists, computational chemists, and bioengineers and explores the options in the spectrum of novel non-volatile memory technologies considered as forerunner of new logic devices.

• 대한전자공학회논문지SD
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• 제41권8호
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• pp.105-113
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• 2004

MRAM (Magneto-resistive Random Access Memory)은 자성체의 스핀 방향을 정보원으로 하는 비휘발성 메모리로 magneto-resistance 물질을 정보 저장 소자로 사용한다. 본 논문에서는 MRAM 시뮬레이션시 MTJ (Magnetic Tunneling Junction)의 hysteretic 특성, asteroid 특성, R-V 특성을 HSPICE에서 재현할 수 있는 새로운 macro-model을 제안하고 HSPICE에 적용하여 그 정확도를 검증하였다. 또한 종래의 reference cell 회로에 비하여 정확한 중간 저항 값을 유지하는 새로운 reference cell 회로를 제안하고 이를 본 논문에서 제안한 macro-model을 이용하여 검증하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.77.1-77.1
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• 2013

Atomic layer deposition (ALD) is known for its self-limiting reaction, which offers atomic-level controllability of the growth of thin films for a wide range of applications. The self-limiting mechanism leads to very useful properties, such as excellent uniformity over a large area and superior conformality on complex structures. These unique features of ALD provide promising opportunities for future electronics. Although the ALD of Al2O3 film (using trimethyl-aluminum and water as a metal precursor and oxygen source, respectively) can be regarded as a representative example of an ideal ALD based on the completely self-limiting reaction, there are many cases deviating from the ideal ALD reaction in recently developed ALD processes. The nonconventional aspects of the ALD reactions may strongly influence the various properties of the functional materials grown by ALD, and the lack of comprehension of these aspects has made ALD difficult to control. In this respect, several dominant factors that complicate ALD reactions, including the types of metal precursors, non-metal precursors (oxygen sources or reducing agents), and substrates, will be discussed in this presentation. Several functional materials for future electronics, such as higher-k dielectrics (TiO2, SrTiO3) for DRAM application, and resistive switching materials (NiO) for RRAM application, will be addressed in this talk. Unwanted supply of oxygen atoms from the substrate or other component oxide to the incoming precursors during the precursor pulse step, and outward diffusion of substrate atoms to the growing film surface even during the steady-state growth influenced the growth, crystal structure, and properties of the various films.