• Journal of Sensor Science and Technology
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• v.2 no.1
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• pp.95-99
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• 1993

a-Si : H TFTs for image sensor have been fabricated and their operational characteristics have been investigated. Hydrogenated amorphous silicon nitride(a-SiN : H) films were used for the gate insulator and $n^{+}$-a-Si : H films were depostied for the source and drain contact. The thicknesses of a-SiN : H and a-Si : H films were $2000{\AA}$, respectively and the thickness of $n^{+}$-a-Si : H film was $500{\AA}$. Also the channel length and channel width of a-Si : H TFTs were $50{\mu}m$ and $1000{\mu}m$, respectively. The ON/OFF current ratio, threshold voltage, and field effect mobility of fabricated a-Si : H TFTs were $10^{5}$, 6.3 V, and $0.15cm^{2}/V{\cdot}s$, respectively.

• KSTLE International Journal
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• v.6 no.2
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• pp.39-44
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• 2005

Friction and wear properties of the Boron carbide ($B_{4}C$) coating 100 nm thickness were studied under various relative humidity (RH). The boron carbide film was deposited on silicon substrate by DC magnetron sputtering method using $B_{4}C$ target with a mixture of Ar and methane ($CH_4$) as precursor gas. Friction tests were performed using a reciprocation type friction tester at ambient environment. Steel balls of 3 mm in diameter were used as counter-specimen. The results indicated that relative humidity strongly affected the tribological properties of boron carbide coating. Friction coefficient decreased from 0.42 to 0.09 as the relative humidity increased from $5\%$ to $85\%$. Confocal microscopy was used to observe worn surfaces of the coating and wear scars on steel balls after the tests. It showed that both the coating surface and the ball were significantly worn-out even though boron carbide is much harder than the steel. Moreover, at low humidity ($5\%$) the boron carbide showed poor wear resistance which resulted in the complete removal of coating layer, whereas at the medium and high humidity conditions, it was not. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analyses were performed to characterize the chemical composition of the worn surfaces. We suggest that tribochemical reactions occurred during sliding in moisture air to form boric acid on the worn surface of the coating. The boric acid and the tribochemcal layer that formed on steel ball resulted in low friction and wear of boron carbide coating.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.148-148
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• 2010

플래시 메모리로 대표되는 비휘발성 메모리는 IT 기술의 발달에 힘입어 급격한 성장세를 나타내고 있지만, 메모리 소자의 크기가 작아짐에 따라서 그 물리적 한계에 이르러 차세대 메모리에 대한 요구가 점차 높아지고 있는 실정이다. 따라서, 이러한 문제점에 대한 대안으로서 고속 동작 및 정보의 저장 시간을 향상 시킬 수 있는 nano-floating gate memory (NFGM)가 제안되었다. Nano-floating gate에서 사용되는 nanocrystal (NCs) 중에서 Si nanocrystal은 비휘발성 메모리뿐만 아니라 발광 소자 및 태양 전지 등의 매우 다양한 분야에 광범위하게 응용되고 있지만, NCs의 크기와 밀도를 제어하는 것이 가장 중요한 문제로 이를 해결하기 위해서 많은 연구가 진행되고 있다. 또한, 소자의 소형화가 이루어지면서 기존의 플래시 메모리 한계를 극복하기 위해서 터널베리어에 관한 관심이 크게 증가했다. 특히, 최근에 많은 주목을 받고 있는 개량형 터널베리어는 크게 VARIOT (VARIable Oxide Thickness) barrier와 CRESTED barrier의 두 가지 종류가 제안되어 있다. VARIOT의 경우에는 매우 얇은 두께의low-k/high-k/low-k 의 적층구조를 가지며, CRESTED barrier의 경우에는 반대의 적층구조를 가진다. 이와 같은 개량형 터널 베리어는 전계에 대한 터널링 전류의 감도를 증가시켜서 쓰기/지우기 특성을 향상시키며, 물리적인 절연막 두께의 증가로 인해 데이터 보존 시간의 향상을 달성할 수 있다. 본 연구에서는 박막의 $SiO_2$와 $Si_3N_4$를 적층한 VARIOT 타입의 개량형 터널 절연막 위에 전하 축적층으로 $SiN_x$층의 내부에 Si-NCs를 갖는 비휘발성 메모리 소자를 제작하였다. Si-NCs를 갖지 않는 $SiN_x$전하 축적층은 Si-NCs를 갖는 전하 축적층보다 더 작은 메모리 윈도우와 열화된 데이터 보존 특성을 나타내었다. 또한, Si-NCs의 크기가 감소됨에 따라 양자 구속 효과가 증가되어 느린 지우기 속도를 보였으나, 데이터 보존 특성이 크게 향상됨을 알 수 있었다. 그러므로, NFGM의 빠른 쓰기/지우기 속도와 데이터 보존 특성을 동시에 만족하기 위해서는 Si-NCs의 크기 조절이 매우 중요하며, NCs크기의 최적화를 통하여 고집적/고성능의 차세대 비휘발성 메모리에 적용될 수 있을 것이라 판단된다.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.705-710
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• 2005

NIL (nanoimprint lithography) technique has demonstrated a high potential for wafer size definition of nanometer as well as micrometer size patterns. During the replication process by NIL, the stiction between the stamp and the polymer is one of major problems. This stiction problem is moi·e important in small sized patterns. An antistiction layer prevents this stiction ana insures a clean demolding process. In this paper, we were using a TCP (transfer coupled plasma) equipment and $C_4F_8$ as a precursor to make a Teflon-like antistiction layer. This antistiction layer was deposited on a 6 inch silicon wafer to have nanometer scale thicknesses. The thickness of deposited antistiction layer was measured by ellipsometry. To optimize the process factor such as table height (TH), substrate temperature (ST), working pressure (WP) and plasma power (PP), we were using a design of experimental (DOE) method. The table of full factorial arrays was set by the 4 factors and 2 levels. Using this table, experiments were organized to achieve 2 responses such as deposition rate and non-uniformity. It was investigated that the main effects and interaction effects between parameters. Deposition rate was in proportion to table height, working pressure and plasma power. Non-uniformity was in proportion to substrate temperature and working pressure. Using a response optimization, we were able to get the optimized deposition condition at desired deposition rate and an experimental deposition rate showed similar results.

• Journal of Surface Science and Engineering
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• v.40 no.4
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• pp.190-196
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• 2007

Dye sensitized solar cells(DSSC) are the most promising future energy resource due to their high energy efficiency, low production cost, and simple manufacturing process. But one problem in DSSC is short life time compared to silicon solar cells. This problem occurred from photocatalytic degradation of dye material by nanometer sized $TiO_2$ particles. To prevent dye degradation as well as to increase its life time, the transparent coating film is needed for UV blocking. In this study, we synthesized nanometer sized $TiO_2$ particles in sols by increasing its internal pressure up to 200 bar in autoclave at $120^{\circ}C$ for 10 hrs. The synthesized $TiO_2$ sols were all formed with brookite phase and their particle size was several nm to 30 nm. Synthesized $TiO_2$ sols were coated on the backside of fluorine doped tin oxide(FTO) glass by ink jet printing method. With increasing coating thickness by repeated ink jet coating, the absorbance of UV region (under 400 nm) also increases reasonably. Decomposition test of titania powders dispersed in 0.1 mM amaranth solution covered with $TiO_2$ coating glass shows more stable dye properties under UV irradiation, compared to that with as-received FTO glass.

• Current Applied Physics
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• v.18 no.12
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• pp.1496-1506
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• 2018

Organic/inorganic ultraviolet photodetector was fabricated using thermal evaporation technique. Organic/inorganic heterojunction based on thermally evaporated copper (II) acetylacetonate thin film of thickness 200 nm deposited on an n-type silicon substrate is introduced. I-V characteristics of the fabricated heterojunction were investigated under UV illumination of intensity $65mW/cm^2$. The diode parameters such as ideality factor, n, barrier height, ${\Phi}_B$, and reverse saturation current, $I_s$, were determined using thermionic emission theory. The series resistance of the fabricated diode was determined using modified Nord's method. The estimated values of series resistance and barrier height of the diode were about $0.33K{\Omega}$ and 0.72 eV, respectively. The fabricated photodetector exhibited a responsivity and specific detectivity about 9 mA/W and $4.6{\times}10^9$ Jones, respectively. The response behavior of the fabricated photodetector was analyzed through ON-OFF switching behavior. The estimated values of rise and fall time of the present architecture under UV illumination were about 199 ms and 154 ms, respectively. Finally, enhancing the photoresponsivity of the fabricated photodetector, post-deposition plasma treatment process was employed. A remarkable modification of the device performance was noticed as a result of plasma treatment. These modifications are representative in a decrease of series resistance and an increase of photoresponsivity and specific detectivity. The process of plasma treatment achieved an increment of external quantum efficiency from 5.53% to 8.34% at -3.5 V under UV illumination.

• Journal of Convergence for Information Technology
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• v.11 no.10
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• pp.270-276
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• 2021

The purpose of this study was to investigate the effects of home care hair treatment characteristics and frequency on hair during permanent wave treatment. The hair treatments distributed on the market were classified into cationic surfactants and silicone oil. Hair treatment was performed 5 times, 10 times, 20 times differently according to the frequency of use, and hair permanent wave was performed. The hair thickness, tensile strength, epidermal observation using SEM, and hair component analysis using EDS were performed as experimental methods. The results of the experiment showed that the natural-derived ingredient was the main ingredient, and the cationic surface activity and silicon oil-free product group had high hair protection effect. Therefore, the product group using natural ingredients should be further researched and developed, and the study on the method and frequency of use of products with irritant chemical ingredients should be conducted.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.798-803
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• 2018

In order to use Si as an anode material for lithium-ion battery, the particle size was controlled to less than $0.5{\mu}m$ and carbon was coated on the surface with the thickness less than 10 nm. The carbon fiber was grown on the Si surface with 50~150 wt%, and the carbon coating was carried out once again. The Si composite material was mixed with dissimilar metals to increase the conductivity, and graphite was mixed to improve cyclic life characteristics. The physical and electrochemical characteristics of composite materials were measured with XRD, SEM, TEM and coin cell. The discharge capacity of Si/PC/CNF/PC was lower than that of Si/PC (Pyrolytic Carbon)/CNF (Carbon Nano Fiber). However, the cyclic life of Si/PC/CNF/PC was higher. Initial discharge capacity of 1512 mA h g-1 at 0.2 C rate and initial efficiency of 78% were shown. It also showed a capacity retention of 94% in 10 cycles.

• Journal of radiological science and technology
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• v.41 no.6
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• pp.561-566
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• 2018

Field-in-Field Technique is applied to the radiation therapy of breast cancer patients, and it is possible to compensate the difference in breast thickness and deliver uniform dose in the breast. However, there are several fields in the treatment field that result in a more complex dose delivery than a single field dose delivery. If the patient's respiration is irregular during the delivery of the dose by several fields and the change of respiration occurs, the dose distribution in the breast changes. Therefore, based on the computed tomography images of breast cancer patients, a human model was created by using a 3D printer (Builder Extreme 1000) to describe the volume in the same manner. A computerized tomography (CT) of the human body model was performed and a treatment plan of 260 cGy / fx was established using a 6-MV field-in-field technique using a computerized treatment planning system (Eclipse 13.6, Varian, USA). The distribution of the dose in the breast according to the change of the respiration was measured using a moving phantom at 0.1 cm, 0.3 cm, 0.5 cm amplitude, using a MOSOXIDE Silicon Field Effect Transistor (MOSFET, Best Medical, Canada) Were measured and compared. The distribution of dose in the breast according to the change of respiration showed similar value within ${\pm}2%$ in the movement up to 0.3 cm compared to the treatment plan. In this experiment, we found that the dose distribution in the breast due to the change of respiration when the change of respiration was increased was not much different from the treatment plan.

• Journal of Korean Dental Hygiene Science
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• v.5 no.1
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• pp.13-19
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• 2022

Background: In this study, zirconia copings were fabricated by setting clinically acceptable inner values for prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM). The processed copings were evaluated for the marginal and internal fit of each abutment shape with a CAD program using the silicone replica technique. Methods A total of 20 copings was produced by selecting models commonly used in clinical practice. After injecting the sample, the minimum thickness, internal adhesion interval, and distance to the margin line were set to 0.5, 0.05, and 1.00 mm using a dental CAD program, respectively. It was measured using a 2D section function in a three-way program of the silicon replication technology. Although the positions and number of measurements of the anterior and posterior regions differed, nine parts of each pre-tube were designated and measured by referring to a previous study to compare the two samples. Results As a result, the average margin of the mesial, distal, and buccal (labial) surfaces was 59.90 ㎛ in the anterior region and 60.40 ㎛ in the posterior region. The mean axial wall margin was 67.25 ㎛ in the anterior region and 69.25 ㎛ in the posterior region. In occlusion, the anterior teeth (77.70 ㎛), posterior teeth (77.60 ㎛), and both anterior and posterior regions were within the clinically acceptable range. Conclusion The edge and inner fit of zirconia coping manufactured using the CAD/CAM system showed clinically applicable results. To reduce errors and increase accuracy, materials and machine errors that affect the manufacture of prosthetics should be investigated. Based on our results, the completeness of prosthetics could increase if the inner value and characteristics of the material are adjusted when applied in clinical practice.