• 한국전기전자재료학회논문지
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• 제29권7호
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• pp.394-399
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• 2016

The silicon dioxide ($SiO_2$) was deposited using various gas as oxygen and nitrous oxide ($N_2O$) in nowadays. In order to improve electrical characteristics and the interface state density ($D_{it}$) in low temperature, It was deposited with carbon dioxide ($CO_2$) and silane ($SiH_4$) gas by inductively coupled plasma chemical vapor deposition (ICP-CVD). Each $D_{it}$ of $SiO_2$ using $CO_2$ and $N_2O$ gas was $1.30{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$ and $3.31{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$. It showed $SiO_2$ using $CO_2$ gas was about 2.55 times better than $N_2O$ gas. After 10 years when the thin film was applied to metal/insulator/semiconductor(MIS)-nonvolatile memory(NVM), MIS NVM using $SiO_2$($CO_2$) on tunneling layer had window memory of 2.16 V with 60% retention at bias voltage from +16 V to -19 V. However, MIS NVM applied $SiO_2$($N_2O$) to tunneling layer had 2.48 V with 61% retention at bias voltage from +20 V to -24 V. The results show $SiO_2$ using $CO_2$ decrease the $D_{it}$ and it improves the operating voltage.

• 폴리머
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• 제38권5호
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• pp.602-612
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• 2014

폴리(디메틸 실록산)(PDMS) 성분을 포함하는 폴리우레탄(PU-Si)을 합성하고 이들의 열적 특성과 형상기억 특성을 분석하였다. 이를 위하여 메틸렌디페닐 디이소시아네이트와 1,4-부탄디올을 하드세그먼트(HS) 성분으로 하고, 소프트세그먼트(SS) 성분으로 PDMS 디올과 폴리(테트라메틸렌 에테르 글리콜)(PTMEG) 혼합폴리올을 사용하여 HS 함량이 각각 23%와 32%이면서 PDMS 함량이 다른 PU-Si를 용액중합법으로 합성하였다. HS 함량이 23%인 PU-Si의 경우 PDMS 함량 증가에 따라 SS의 냉결정화온도($T_{cc}$)와 용융결정화온도는 증가하였으나 용융온도($T_m$)에는 변화가 없었다. HS 함량이 32%인 시료들의 경우 PTMEG의 $T_m$이 HS 함량 23%인 시료들보다 약간 높은 온도에서 나타났으며 $T_{cc}$는 관찰되지 않았다. PDMS 성분이 포함된 PU-Si 필름들은 PU에 비해 형태고정성은 약간 좋지 않지만 형상기억 효과는 더 우수하였다.

• 한국전기전자재료학회논문지
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• 제33권6호
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• pp.445-449
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• 2020

Non-volatile memory is approaching its fundamental limits with the Si₃N₄ storage layer, necessitating the use of alternative materials to achieve a higher programming/erasing speed, larger storage window, and better data retention at lower operating voltage. This limitation has restricted the development of the charge-trap memory, but can be addressed by using high-k dielectrics. The paper reviews the doping of nitrogen, titanium, and yttrium on high-k dielectrics as a storage layer by comparing MONOS devices with different storage layers. The results show that nitrogen doping increases the storage window of the Gd₂O₃ storage layer and improves its charge retention. Titanium doping can increase the charge capture rate of HfO₂ storage layer. Yttrium doping increases the storage window of the BaTiO₃ storage layer and improves its fatigue characteristics. Parameters such as the dielectric constant, leakage current, and speed of the memory device can be controlled by maintaining a suitable amount of external impurities in the device.

• 한국정보통신학회논문지
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• 제11권9호
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• pp.1717-1723
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• 2007

본 연구에서는 PLZT(10/30/70), PLT(10), PZT(30/70) 강유전체 박막을 이용한 quasi-MFISFET (Metal-Ferroelectric-Insulator-Semiconductor FET) 소자를 제작하여 드레인 전류 특성을 조사하였다. 이로부터, quasi-MHSFET 소자의 드레인 전류 크기가 강유전체 박막의 분극 크기에 따라 직접적인 영향을 받으며 결정된다는 사실을 알 수 있었다. 또, ${\pm}5V$ 와 ${\pm}10V$의 게이트 전압변화를 주었을 때 메모리 윈도우는 각각 0.5V 와 1.3V 이었고, 강유전체 박막에 인가되는 전압에 의해 만들어지는 항전압의 변동에 따라 메모리 윈도우가 변화된다는 사실을 확인할 수 있었다. MFISFET 소자의 retention 특성을 알아보기 위 해 PLZT(10/30/70) 박막의 전기장과 시간지연에 따른 누설전류 특성을 측정하여 전류밀도 상수 $J_{ETO}$, 전기장 의존 요소 K, 시간 의존 요소 m을 구하고, 이들 파라미터를 이용하여 시간에 따른 전하밀도의 변화를 정량적으로 분석하였다.

• 대한본초학회지
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• 제29권6호
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• pp.73-83
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• 2014

Objectives : This study was investigated the effects of the root of Polygala tenuifolia (POL) on learning and memory impairment induced by chronic cerebral hypoperfusion in rats. Methods : Chronic cerebral hypoperfusion was produced by permanent bilateral common carotid artery occlusion (pBCAO). POL was administered orally once a day (130 mg/kg of water-extract) for 28 days starting at 4 weeks after the pBCAO. The acquisition of learning and the retention of memory were tested on 9th week after the pBCAO using the Morris water maze. In addition, effects of POL on $A{\beta}$ generation and expressions of APP and BACE1 were observed in the hippocampus of rats. Results : POL significantly prolonged the swimming time spent in target quadrant and significantly reduced the swimming time spent in the quadrant far from the target. POL significantly increased the percentage of swim in the targer quadrant in the retention test, while POL was not effective on the escape latencies in the acquisition training trials. POL significantly reduced the levels of $A{\beta}_{(1-40)}$ and $A{\beta}_{(1-42)}$ in the cerebral cortex and the level of $A{\beta}_{(1-42)}$ in the hippocampus produced by chronic cerebral hypoperfusion. POL also significantly attenuated the up-regulation of APP and BACE1 expression in the hippocampus produced by chronic cerebral hypoperfusion. Conclusions : The results show that POL alleviated memory deficit and up-regulation of $A{\beta}$ and BACE1 expressions in the hippocampus. This result suggests that POL may exert ameliorating effect on memory deficit through inhibition of ${\beta}$-secretase activity and $A{\beta}$ generation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.410-410
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• 2013

Next-generation nonvolatile memory (NVM) has attracted increasing attention about emerging NVMs such as ferroelectric random access memory, phase-change random access memory, magnetic random access memory and resistance random access memory (RRAM). Previous studies have demonstrated that RRAM is promising because of its excellent properties, including simple structure, high speed and high density integration. Many research groups have reported a lot of metal oxides as resistive materials like TiO2, NiO, SrTiO3 and ZnO [1]. Among them, the ZnO-based film is one of the most promising materials for RRAM because of its good switching characteristics, reliability and high transparency [2]. However, in many studies about ZnO-based RRAMs, there was a problem to get lower current level for reducing the operating power dissipation and improving the device reliability such an endurance and an retention time of memory devices. Thus in this paper, we investigated that highly reproducible bipolar resistive switching characteristics of W doped ZnO RRAM device and it showed low resistive switching current level and large ON/OFF ratio. This may be caused by the interdiffusion of the W atoms in the ZnO film, whch serves as dopants, and leakage current would rise resulting in the lowering of current level [3]. In this work, a ZnO film and W doped ZnO film were fabricated on a Si substrate using RF magnetron sputtering from ZnO and W targets at room temperature with Ar gas ambient, and compared their current levels. Compared with the conventional ZnO-based RRAM, the W doped ZnO ReRAM device shows the reduction of reset current from ~$10^{-6}$ A to ~$10^{-9}$ A and large ON/OFF ratio of ~$10^3$ along with self-rectifying characteristic as shown in Fig. 1. In addition, we observed good endurance of $10^3$ times and retention time of $10^4$ s in the W doped ZnO ReRAM device. With this advantageous characteristics, W doped ZnO thin film device is a promising candidates for CMOS compatible and high-density RRAM devices.

• 동의생리병리학회지
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• 제25권2호
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• pp.300-305
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• 2011

The present study was investigated the neuroprotective effects of acupuncture at ST36 on learning and memory deficits after transient cerebral ischemia in a gerbil model. The animals were randomly divided into three groups (n=7 in each group): the sham operation group (SHAM), ischemia-induced and ST36 acupuncture group (ISC + ST36), and the ischemia-induced and Tail-acupuncture group (ISC + TAIL). For the acupuncture stimulation, stainless steel needles, 0.3 mm in diameter, were inserted bilaterally into the ST36 locus or the tail and stimulated for 1 min/day for 14 days. Using the Morris water maze test, the animals were tested on spatial learning and memory. In addition, the effects of acupuncture on memory storage and the choline acetyltransferase (ChAT) activity, in the hippocampal CA1 area, were investigated by ChAT immunohistochemistry. Transient cerebral ischemia produced impaired performance on the MWM test (DAY 5: p<0.01 and retention test: p<0.05) and severely decreased ChAT immunoreactivity in the CA1 hippocampal area compared to the SHAM group (p<0.05). However, improved learning and memory were observed (DAY 5: p<0.05 and retention test: p<0.01) as well as a significantly reduced loss of ChAT immunoactivity in the hippocampal CA1 region (p<0.001) after acupuncture stimulation at ST36 were observed. These results show that acupuncture at ST36 ameliorated the learning and memory deficits at least in part through the cholinergic system. The findings of this study provide potential data that acupuncture is useful for the treatment of some of the behavioral impairs of transient cerebral ischemia.

• 대한한의학회지
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• 제23권2호
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• pp.125-138
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• 2002

Learning and memory are essential requirements for every living organism in order to cope with environmental demands, and cholinergic systems are known to be involved in learning and memory. Scutellaria baicalensis (SB) and Gastrodia elata (GE) as a traditional Oriental medicine have been clinically used to treat or prevent memory deficits, including Alzheimer's disease. In the present study, we investigated the effects of SB and GE on learning and memory in the Morris water maze task and the central cholinergic system of the rats with excitotoxic medial septum lesions. In the water maze test, the animals were trained to find a platform at a fixed position over 6 days and then received a 60-s probe trial in which the platform was removed from the pool on the 7th day. Ibotenic lesion of the medial septum (MS) impaired their performance in the maze test (latency of acquisition test on the 3rd day, $27.6{\pm}$4.4 sec vs. $61.7{\pm}17.7$ sec; retention test, $7.9{\pm}1.3%$ vs. $5.7{\pm}1.0%$: sharn vs. ibotenic lesioned groups, respectively) and reduced choline acetyltransferase (ChAT) - immunoreactivity in the MS and the hippocarnpus, which is a marker for degeneration of the central cholinergic system (number of cells, $21.1{\pm}1.1$ vs. $13.2{\pm}1.3$: sham vs. ibotenic lesioned group). Daily administrations of SB (100mg/kg, p.o.) and GE (100mg/kg, p.o.) for 21 consecutive days produced significant reversals of ibotenic acid-induced deficit in learning and memory. These treatments also reduced the loss of cholinergic immunoreactivity in the MS and the hippocarnpus induced by ibotenic acid. These results demonstrated that SB and GE ameliorated learning and memory deficits through effects on the central nervous system, partly through effect on the acetylcholine system. Our studies suggest an evidence of SB and GE as treatment for Alzheimer's disease.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.130-134
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• 2015

This research proposes the use of a composition modulated (ZrO₂)_x(Al₂O₃)_1-x film as a charge trapping layer for charge trap flash memory; this is possible when the Zr (Al) atomic percent is controlled to form a variable bandgap as identified by the valence band offsets and electron energy loss spectrum measurements. Compared to memory devices with uniform compositional (ZrO₂)_0.1(Al₂O₃)_0.9 or a (ZrO₂)_0.92(Al₂O₃)_0.08 trapping layer, the memory device using the composition modulated (ZrO₂)_x(Al₂O₃)_1-x as the charge trapping layer exhibits a larger memory window (6.0 V) at the gate sweeping voltage of ±8 V, improved data retention, and significantly faster program/erase speed. Improvements of the memory characteristics are attributed to the special energy band alignments resulting from non-uniform distribution of elemental composition. These results indicate that the composition modulated (ZrO₂)_x(Al₂O₃)_1-x film is a promising candidate for future nonvolatile memory device applications.

• 한국전기전자재료학회논문지
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• 제15권7호
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• pp.576-582
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• 2002

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectrics were fabricated, and nitrogen distribution and bonding species which contribute to memory characteristics were analyzed. Also, memory characteristics of devices depending on the anneal temperatures were investigated. The devices were fabricated by retrograde twin well CMOS processes with $0.35\mu m$ design rule. The processes could be simple by in-situ process in growing dielectric. The nitrogen distribution and bonding states of gate dielectrics were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). As the nitridation temperature increased, nitrogen concentration increased linearly, and more time was required to form the same reoxidized layer thickness. ToF-SIMS results showed that SiON species were detected at the initial oxide interface which had formed after NO annealing and $Si_2NO$ species within the reoxidized layer formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. It could be said that nitrogen concentration near initial interface is limited to a certain quantity, so the excess nitrogen is redistributed within reoxidized layer and contribute to electron trap generation.