• Korean Journal of Materials Research
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• v.19 no.4
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• pp.203-206
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• 2009

$Sn_XSe_{100-X}$ (15|X|30) alloys have been studied to explore their suitability as phase change materials for nonvolatile memory applications. The phase change characteristics of thin films prepared by a Radio Frequency (RF) magnetron co-sputtering system were analyzed by an X-ray diffractometer and 4-point probe measurement. A phase change static tester was also used to determine their crystallization under the pulsed laser irradiation. X-ray diffraction measurements show that the transition in sheet resistance is accompanied by crystallization. The amorphous state showed sheet resistances five orders of magnitude higher than that of the crystalline state in $Sn_XSe_{100-X}$ (x = 15, 20, 25, 30) films. In the optimum composition, the minimum time of $Sn_XSe_{100-X}$ alloys for crystallization was 160, 140, 150, and 30ns at 15mW, respectively. The crystallization temperature and the minimum time for crystallization of thin films were increased by increasing the amount of Sn, which is correlated with the activation energy for crystallization.

• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.63-66
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• 2013

This paper describes the highly productive process technologies of microprobe arrays, which were used for a probe card to test a Dynamic Random Access Memory (DRAM) chip with fine pitch pads. Cantilever-type microprobe arrays were fabricated using conventional micro-electro-mechanical system (MEMS) process technologies. Bonding material, gold-tin (Au-Sn) paste, was used to bond the Ni-Co alloy microprobes to the ceramic space transformer. The electrical and mechanical characteristics of a probe card with fabricated microprobes were measured by a conventional probe card tester. A probe card assembled with the fabricated microprobes showed good x-y alignment and planarity errors within ${\pm}5{\mu}m$ and ${\pm}10{\mu}m$, respectively. In addition, the average leakage current and contact resistance were approximately 1.04 nA and 0.054 ohm, respectively. The proposed highly productive microprobes can be applied to a MEMS probe card, to test a DRAM chip with fine pitch pads.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.433-438
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• 2020

To enhance the tunneling electroresistance (TER) ratio of a ferroelectric tunnel junction (FTJ) device using Al-doped HfO₂ thin films, a thin insulating layer was prepared on a TiN bottom electrode, for which TiN was preliminarily treated at various temperatures in O₂ ambient. The composition and thickness of the inserted insulating layer were optimized at 600℃ and 50 Torr, and the FTJ showed a high TER ratio of 430. During the heat treatments, a titanium oxide layer formed on the surface of TiN, that suppressed oxygen vacancy generation in the ferroelectric thin film. It was found that the fabricated FTJ device exhibits two distinct resistance states with higher tunneling currents by properly heat-treating the TiN bottom electrode of the HfO₂-based FTJ devices in O₂ ambient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.118-119
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• 2006

In the present work, we investigate the basic physical and thermal properties and electrical resistance change due to phase change in chalcogenide-based $Ge_1Se_1Te_2$ and $Ge_2Se_2Te_5$ thin films. The phase transition from amorphous to crystalline states, and vice versa, of $Ge_1Se_1Te_2$ and $Ge_2Se_2Te_5$ thin films by applying electrical pulses have been studied. The reversible phase transition between the amorphous and crystalline states, which is accompanied by a considerable change in electrical resistivity, is exploited as means to store bits of information.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.171-171
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• 2007

Dysprosium-doped bismuth titanate (BDT) thin films were successfully deposited on Pt(111)/Ti/$SiO_2$/Si(100) substrates by liquid delivery MOCVD process and their structural and ferroelectric properties were characterized. Fabricated BDT thin films were found to be random orientations, which were confirmed by X-ray diffraction experiment and scanning electron microscope analysis. The crystallinity of the BDT films was improved and the average grain size increased as the crystallization temperature increased from 600 to $720^{\circ}C$ at an interval of $40^{\circ}C$. The BDT thin film annealed at $720^{\circ}C$ showed a large remanent polarization (2Pr) of $52.27\;{\mu}C/cm^2$ at an applied voltage of 5V. The BDT thin film exhibits a good fatigue resistance up to $1.0{\times}10^{11}$ switching cycles at a frequency of 1 MHz with applied pulse of ${\pm}5\;V$. These results indicate that the randomly oriented BDT thin film is a promising candidate among ferroelectric materials useti비 in lead-free nonvolatile ferroelectric random access memory applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.242.1-242.1
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• 2013

최근, 저항변화 메모리 (resistance random access memory, ReRAM)는 단순한 구조, 고집적성, 낮은 소비 전력, 우수한 retention 특성 CMOS 기술과의 공정호환성 등의 장점으로 인하여 현재 사용되는 메모리의 물리적 한계를 극복할 수 있는 차세대 메모리로써 주목을 받고 있다. 더욱이 용액공정은 높은 균일성, 공정 시간 및 비율 감소 그리고 대면적화가 가능한 장점을 가진 이유로 TiOx, ZrOx ZnO 같은 high-k 물질들을 이용한 연구가 보고되고 있다. 기존의 ReRAM 용액공정에서 결함, 즉 oxygen vacancies 그리고 불순물들을 제어하기 위해 일반적으로 사용되는 furnace 열처리는 낮은 열효율과 고비용등의 문제점을 가지고 있다. 특히 glass 또는 flexble 기판의 경우 열처리 온도에 제약이 있다. 이러한 문제를 해결하기 위한 방법으로 열 균일성, 짧은 공정시간 의 장점을 가진 microwave 열처리 방법이 보고되고 있다. 따라서 본 연구에서는 용액공정을 이용하여 증착한 HfOx 기반의 저항변화 메모리를 제작하여 저온에서 microwave 열처리 와 furnace 열처리의 특성을 비교평가 하였다. 그 결과 microwave 열처리 방법이 furnace 열처리 방법보다 넓은 메모리 마진, 향상된 uniformity 를 가지는 것을 확인 하였다. 이로써 저온공정이 필요한 ReRAM 의 열처리 대안책 으로 사용될 수 있을 것으로 기대된다.

• Smart Structures and Systems
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• v.24 no.2
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• pp.157-171
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• 2019

This study investigated the effects of the geometric parameters of superelastic shape memory alloy (SE SMA) fibers on the pullout displacement recovering and self-healing capacity of reinforced cementitious composites. Three diameters of 0.5, 0.7 and 1.0 mm and two different crimped lengths of 5.0 and 10.0 mm were considered. To provide best anchoring action and high bond between fiber and cement mortar, the fibers were crimped at the end to create spear-head shape. The single fiber cement-based specimens were manufactured with the cement mortar of a compressive strength of 84 MPa with the square shape at the top and a dog-bone shape at the bottom. The embedded length of each fiber was 15 mm. The pullout test was performed with displacement control to obtain monotonic or hysteretic behaviors. The results showed that pullout displacements were recovered after fibers slipped and stuck in the specimen. The specimens with fiber of larger diameter showed better displacement recovering capacity. The flag-shaped behavior was observed for all specimens, and those with fiber of 1.0 mm diameter showed the clearest one. It was observed that the length of fiber anchorage did not have a significant effect on the displacement recovery, pullout resistance and self-healing capacity.

• Clinical Nutrition Research
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• v.13 no.2
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• pp.121-129
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• 2024

The prevalence of metabolic syndrome caused by diets containing excessive fatty acids is increasing worldwide. Patients with metabolic syndrome exhibit abnormal lipid profiles, chronic inflammation, increased levels of saturated fatty acids, impaired insulin sensitivity, excessive fat accumulation, and neuropathological issues such as memory deficits. In particular, palmitic acid (PA) in saturated fatty acids aggravates inflammation, insulin resistance, impaired glucose tolerance, and synaptic failure. Recently, adiponectin, brain-derived neurotrophic factor (BDNF), and glucose-like peptide-1 (GLP-1) have been investigated to find therapeutic solutions for metabolic syndrome, with findings suggesting that they are involved in insulin sensitivity, enhanced lipid profiles, increased neuronal survival, and improved synaptic plasticity. We investigated the effects of adiponectin, BDNF, and GLP-1 on neurite outgrowth, length, and complexity in PA-treated primary cortical neurons using Sholl analysis. Our findings demonstrate the therapeutic potential of adiponectin, BDNF, and GLP-1 in enhancing synaptic plasticity within brains affected by metabolic imbalance. We underscore the need for additional research into the mechanisms by which adiponectin, BDNF, and GLP-1 influence neural complexity in brains with metabolic imbalances.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.80-87
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• 2015

Memristor is a new kind of memory device whose resistance varies depending upon applied charge and whose previous resistance state is preserved even when its power is off. Ordinary memristor has a nonlinear programming characteristics about time when a constant voltage is applied. For the easiness of programming, it is desirable that resistance is programmed linearly about time. We had proposed previously a memristor bridge configuration with which weight can be programmed nicely in positive, negative or zero. In memristor bridge circuit, two memristors are connected in series with different polarity. Memristors are complementary each other and it follows that the memristance variation is linear with respect to time. In this paper, the linearization effect of weight programming of memristor bridge synapse is investigated and verified about both $TiO_2$ memristor from HP and a nonlinear memristor with a window function. Memristor bridge circuit would be helpful to conduct synaptic weight programming.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.1
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• pp.115-122
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• 2014

In this paper, reliability is secured by sensing a post-program resistance of several tens of kilo ohms and restricting a read current flowing over an unblown eFuse within $100{\mu}A$ since RWL driver and BL pull-up load circuits using a regulated voltage of V2V ($=2V{\pm}10%$) are proposed to have a wide operating voltage range for eFuse OTP memory. Also, when a comparison of a cell array of 1 row ${\times}$ 32 columns with that of 4 rows ${\times}$ 8 columns is done, the layout size of 4 rows ${\times}$ 8 columns is smaller with $187.065{\mu}m{\times}94.525{\mu}m$ ($=0.01768mm^2$) than that of 1 row ${\times}$ 32 columns with $735.96{\mu}m{\times}61.605{\mu}m$ ($=0.04534mm^2$).