• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.87-94
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• 2016

In order to improve performances of submicrometer-sized Si negative electrode which shows larger volumetric change than nano-sized Si, composite binders are introduced by blending between poly(phenanthrenequinone) (PPQ) conductive polymer binder and poly(acrylic acid) (PAA) having good adhesion strength due to its carboxyl functional group. Blending between PPQ and PAA shows an effect that the adhesion strength of the Si electrode with the composite conductive binder is greatly improved after blending and this makes its better stable cycle performance. Blending ratios between PPQ and PAA in this work are 2:1, 1:1, 1:2 (by weight) and the best capacity retention at 50th cycle is observed in the electrode with the blending ratio 2:1 (named QA21). This is because that PPQ plays a role of conductive carbon among the Si particles or between Si particles and Cu current collector and PAA binds effectively the particles and the current collector. According to this synergetic effect, the internal resistance of the Si electrode with the blending ratio 2:1 is the smallest value. In addition, the Si electrode with PPQ-PAA composite binder shows the better stable cycle performance than the electrode with conventional super-P conductive carbon (20 wt.%).

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.47-50
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• 2008

A new anode composition material comprising of SiO and Graphite has been prepared by adopting High energy ball milling (HEBM) technique. The anode material shows high initial charge and discharge capacity values of 1139 and 568 mAh/g, respectively. The electrode sustains reversible discharge capacity value of 719 mAh/g at 30th cycle with a high coulombic efficiency${\sim}99%$. Since the materials formed during initial charge process the nano silicon/$Li_4SiO_3$ and $Li_2O$ remains as interdependent, it may be expected that the composite exhibiting higher amount of irreversibility$(Li_2O)$ will deliver higher reversible capacity. In this study, constant current-constant voltage (CC-CV) charge method was employed in place of usual constant current (CC) method in order to convert efficiently all the SiO particles which resulted high initial discharge capacity at the first cycle. We improved considerably the initial discharge specific capacity of SiO/G composite by pretreatment(CC-CV).

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.39-45
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• 2012

Three-dimensional integrated circuit(3D IC) technology has become increasingly important due to the demand for high system performance and functionality. In this work, BOE and HF wet etching of Cu line surfaces after CMP were conducted for Cu-Cu pattern direct bonding. Step height of Cu and $SiO_2$ as well as Cu dishing after Cu CMP were analyzed by the 3D-Profiler. Step height increased and Cu dishing decreased with increasing BOE and HF wet etching times. XPS analysis of Cu surface revealed that Cu surface oxide layer was partially removed by BOE and HF wet etching treatment. BOE treatment showed not only the effective $SiO_2$ etching but also reduced dishing and Cu surface oxide rather than HF treatment, which can be used as an meaningful process data for reliable Cu-Cu pattern bonding characteristics.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.155-159
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• 2003

We report on the annealing effect and ferromagnetic characteristics of Zn$_{0.7}$Mn$_{0.3}$O film prepared by sol-gel method on the silicon (100) substrate using field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry. Magnetic measurements show thatZn$_{0.7}$Mn$_{0.3}$O films exhibit ferromagnetism at 5 K revealing the coercive field of ∼110 Oe for as grown sample and 360, 1035 Oe for samples annealed at 700, 800 $^{\circ}C$, respectively. Our experimental evidence suggests that ferromagnetic precipitates of a manganese oxide may be responsible for the observed ferromagnetic behaviors of the film.he film.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.44-45
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• 2010

We are currently conducting studies on culturing and biocompatibility assessment of various cells such as neural stem cells and induced pluripotent stem cells(IPS cells) on carbon nanotube (CNT), on nerve regeneration electrodes, and on silicon wafers with a focus on developing nerve integrated CNT based bio devices for interfacing with living organisms, in order to develop brain-machine interfaces (BMI). In addition, we are carried out the chemical modification of carbon nanotube (mainly SWCNTs)-based bio-nanosensors by the plasma ion irradiation (plasma activation) method, and provide a characteristic evaluation of a bio-nanosensor using bovine serum albumin (BSA)/anti-BSA binding and oligonucleotide hybridization. On the other hand, the researches in the case of "novel plasma" have been widely conducted in the fields of chemistry, solid physics, and nanomaterial science. From the above-mentioned background, we are conducting basic experiments on direct irradiation of body tissues and cells using a micro-spot atmospheric pressure plasma source. The device is a coaxial structure having a tungsten wire installed inside a glass capillary, and a grounded ring electrode wrapped on the outside. The conditions of plasma generation are as follows: applied voltage: 5-9 kV, frequency: 1-3 kHz, helium (He) gas flow: 1-1.5 L/min, and plasma irradiation time: 1-300 sec. The experiment was conducted by preparing a culture medium containing mouse fibroblasts (NIH3T3) on a culture dish. A culture dish irradiated with plasma was introduced into a $CO_2$-incubator. The small animals used in the experiment involving plasma irradiation into living tissue were rat, rabbit, and pick and are deeply anesthetized with the gas anesthesia. According to the dependency of cell numbers against the plasma irradiation time, when only He gas was flowed, the growth of cells was inhibited as the floatation of cells caused by gas agitation inside the culture was promoted. On the other hand, there was no floatation of cells and healthy growth was observed when plasma was irradiated. Furthermore, in an experiment testing the effects of plasma irradiation on rats that were artificially given burn wounds, no evidence of electric shock injuries was found in the irradiated areas. In fact, the observed evidence of healing and improvements of the burn wounds suggested the presence of healing effects due to the growth factors in the tissues. Therefore, it appears that the interaction due to ion/radicalcollisions causes a substantial effect on the proliferation of growth factors such as epidermal growth factor (EGF), nerve growth factor (NGF), and transforming growth factor (TGF) that are present in the cells.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.901-908
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• 2018

Graphite is used as a sample anode active material. However, since the maximum theoretical capacity is limited to $372mA\;h\;g^{-1}$, a new anode active material is required for the development of a high capacity lithium ion battery. The maximum theoretical capacity of Si is $4200mA\;h\;g^{-1}$, which is higher than that of graphite. However, it is not suitable for direct application to the anode active material because it has a volume expansion of 400%. In order to minimize the decrease of the discharge capacity due to the volume expansion, the Si was pulverized by the dry method to reduce the mechanical stress and the volume change of the reaction phase, and the change of the volume was suppressed by coating the carbon layers to the particle size controlled Si particles. And carbon fiber is grown like a thread on the particle surface to control secondary volume expansion and improve electrical conductivity. The physical and chemical properties of the materials were measured by XRD, SEM and TEM, and their electrochemical properties were evaluated. In this study, we have investigated the synthesis method that can be used as anode active material by improving cycle characteristics of Si.

• Clean Technology
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• v.24 no.4
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• pp.332-338
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• 2018

Currently graphite is used as an anode active material for lithium ion battery. However, since the maximum theoretical capacity of graphite is limited to $372mA\;h\;g^{-1}$, a new anode active material is required for the development of next generation high capacity and high energy density lithium ion battery. The maximum theoretical capacity of Si is $4200mA\;h\;g^{-1}$, which is about 10 times higher than the maximum theoretical capacity of graphite. However, since the volume expansion rate is almost 400%, the irreversible capacity increases as the cycle progresses and the discharge capacity relative to the charge is remarkably reduced. In order to solve these problems, it is possible to control the particle size of the Si anode active material to reduce the mechanical stress and the volume change of the reaction phase, thereby improving the cycle characteristics. Therefore, in order to minimize the decrease of the charge / discharge capacity according to the volume expansion rate of the Si particles, the improvement of the cycle characteristics was carried out by pulverizing Si by a dry method with excellent processing time and cost. In this paper, Si is controlled to nano size using vibrating mill and the physicochemical and electrochemical characteristics of the material are measured according to experimental variables.