• 반도체디스플레이기술학회지
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• 제9권4호
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• pp.25-29
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• 2010

We have investigated the effect of surface roughness of TCO substrate on the characteristics of OLED (organic light emitting diodes) devices. In order to control the surface roughness of AZO thin films, we have processed photo-lithography and reactive ion etching. The micro-size patterned mask was used, and the etching depth was controlled by changing etching time. The surface morphology of the AZO thin film was observed by FESEM and atomic force microscopy (AFM). And then, organic materials and cathode electrode were sequentially deposited on the AZO thin films. Device structure was AZO/${\alpha}$-NPD/DPVB/$Alq_3$/LiF/Al. The DPVB was used as a blue emitting material. The electrical characteristics such as current density vs. voltage and luminescence vs. voltage of OLED devices were measured by using spectrometer. The current vs. voltage and luminance vs. voltage characteristics were systematically degraded with increasing surface roughness. Furthermore, the retention test clearly presented that the reliability of OLED devices was directly influenced with the surface roughness, which could be interpreted in terms of the concentration of the electric field on the weak and thin organic layers caused by the poor step coverage.

• Safety and Health at Work
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• 제9권1호
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• pp.17-24
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• 2018

Background: Increasing the slip resistance of floor surfaces would be desirable, but there is a lack of evidence on whether traction properties are linearly correlated with the topographic features of the floor surfaces or what scales of surface roughness are required to effectively control the slipperiness of floors. Objective: This study expands on earlier findings on the effects of floor surface finishes against slip resistance performance and determines the operative ranges of floor surface roughness for optimal slip resistance controls under different risk levels of walking environments. Methods: Dynamic friction tests were conducted among three shoes and nine floor specimens under wet and oily environments and compared with a soapy environment. Results: The test results showed the significant effects of floor surface roughness on slip resistance performance against all the lubricated environments. Compared with the floor-type effect, the shoe-type effect on slip resistance performance was insignificant against the highly polluted environments. The study outcomes also indicated that the oily environment required rougher surface finishes than the wet and soapy ones in their lower boundary ranges of floor surface roughness. Conclusion: The results of this study with previous findings confirm that floor surface finishes require different levels of surface coarseness for different types of environmental conditions to effectively manage slippery walking environments. Collected data on operative ranges of floor surface roughness seem to be a valuable tool to develop practical design information and standards for floor surface finishes to efficiently prevent pedestrian fall incidents.

• 오토저널
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• 제8권3호
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• pp.68-76
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• 1986

The surface rolling method which is one of the plastic deformation processes increases the surface roughness and hardness of materials. In this study, three NACHI6000 ZZ bearing were used for surface rolling tool on the mild steel and high carbon steel. The purpose of this study is to investigate the effects of rolling speed, feed rate and contact pressure on the surface roughness. The following results have been obtained with the mild steel and high carbon steel. 1. The roller finishing method has increased surface roughness from 2.4 .mu.m Ra at initial ground surface to 0.17 .mu.m Ra-0.4 .mu.m Ra. 2. The contact pressure has influenced greatly on the surface roughness. There is an optimal contact pressure. 3. As the rolling speed and the feed rate decrease, the surface roughness improves. 4. The optimal contact pressure for the good surface roughness of SS40 and STC 3 has been at 213 Kgf/Cm$^{2}$ and 220 Kgf/Cm$^{2}$ respectively.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.89-94
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• 2001

This paper presents a study of surface roughness prediction model by orthogonal design in turning operation. Regression analysis technique has been used to study the effects of the cutting parameters such as cutting speed, feed depth of cut, and nose radius on surface roughness. An effect of interaction between two parameters on surface roughness has also been investigated. The experiment has been conducted using coated tungsten carbide inserts without cutting fluid. The reliability of the surface roughness model as a function of the cutting parameters has been estimated. The results show that the experimental design used in turning process is a method to estimate the effects of cutting parameters on sur-face roughness.

• 오토저널
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• 제9권5호
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• pp.57-65
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• 1987

The surface rolling method which is one of the plastic deformation processes increases the surface roughness with reduction of diameter and hardness. In this study, three NACHI 6000 ZZ bearing were used for surface rolling tool on a mild steel The following results have been obtained with the mild steel. 1) The load is major factor in getting fine surface roughness of roller finishing after grinding The optimal surface roughness of SS41 steel can be obtained at the contact pressure of 210 kgf/cm$^{2}$. 2) At the contact pressure range of 200kgf/cm$^{2}$-210kgf/cm$^{2}$ for optimal surface roughness, The surface hardness increased to Hv200-Hv240 from Hv 125 before surface rolling. 3) Within the diameter variation of 13 .mu.m the surface roughness and the surface hardness were increased, but out of variation of 14.mu.m. The surface roughness become worse and the surface hardness was increased.

• Tribology and Lubricants
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• 제35권6호
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• pp.323-329
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• 2019

Sapphire is currently used as a substrate material for blue light-emitting diodes (LEDs). The market for sapphire substrates has expanded rapidly as the use of LEDs has extended into various industries. However, sapphire is classified as one of the most difficult materials to machine due to its hardness and brittleness. Recently, a lap-grinding process has been developed to combine the lapping and diamond mechanical polishing (DMP) steps in a single process. This paper studies, the effect of wafer surface roughness on the chemical mechanical polishing (CMP) process by pressure and abrasive concentration in the lap-grinding process of a sapphire wafer. In this experiment, the surface roughness of a sapphire wafer is measured after lap-grinding by varying the pressure and abrasive concentration of the slurry. CMP is carried out under pressure conditions of 4.27 psi, a plate rotation speed of 103 rpm, head rotation speed of 97 rpm, and slurry flow rate of 170 ml/min. The abrasive concentration of the CMP slurry was 20wt, implying that the higher the surface roughness after lapgrinding, the higher the material removal rate (MRR) in the CMP. This is likely due to the real contact area and actual contact pressure between the rough wafer and polishing pad during the CMP. In addition, wafers with low surface roughness after lap-grinding show lower surface roughness values in CMP processes than wafers with high surface roughness values; therefore, further research is needed to obtain sufficient surface roughness before performing CMP processes.

• 한국응용과학기술학회지
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• 제41권1호
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• pp.46-57
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• 2024

In this study, the various process conditions for high-power DC Magnetron Sputtering (DCMS) on the surface roughness of carbon thin films were investigated. The optimal conditions for Si/C coating were 40min for deposition time, which does not deviate from normal plasma, to obtain the maximum deposition rate, and the conditions for the best surface roughness were -16volt bias voltage and 400watt DC power with 1.3x10-3torr chamber pressure. Under these optimal conditions, an excellent carbon thin film with a surface roughness of 1.62nm and a thickness of 724nm was obtained. As a result of XPS analysis, it was confirmed that the GLC structure (sp² bonding) was more dominant than the DLC structure (sp³ bonding) in the thin film structure of the carbon composite layer formed by DC sputtering. Except in infrequent cases of relatively plasma instability, the lower bias voltage and applied power induces smaller surface roughness value due to the cooling effect and particle densification. For the optimal conditions for Graphite/C composite layer coating, a roughness of 36.3 nm and a thickness of 711 nm was obtained under the same conditions of the optimal process conditions for Si/C coating. This layer showed a immensely low roughness value compared to the roughness of bare graphite of 242 nm which verifies that carbon coating using DC sputtering is highly effective in modifying the surface of graphite molds for glass forming.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.109-114
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• 1992

This paper describes an effect of operating condition on surface roughness in wire-cut FDM. The experimental values of surface roughness were measured by the test pieces under the condition of changing. On time, Off time, and Feed rate after fixing other conditions. The material of the test pieces is the alloy tool steel(STD 11) and was used after heat treatment. The results are as follows: 1. The surface roughness became rapidly worse according to the increase of On time and Feed rate. 2. The surface roughness became slowly better according to the increase of Off time.

• 한국터널지하공간학회 논문집
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• 제7권4호
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• pp.269-283
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• 2005

기존의 전단강도 모델에서 거칠기와 전단강도를 실제보다 과소평가 하고 있는 문제의 원인을 파악하기 위하여 먼저 거칠기의 발현 특성, 거칠기 계수의 특성, 거칠기 계수에 미치는 측정 간격과 만곡 (waviness)의 효과 등을 검토하였다. 그 결과, 이러한 문제에는 거칠기의 발현특성의 고려 부족, 거칠기 계수의 오용, 거칠기의 측정 과정에서의 엘리어싱 (aliasing)이 중요한 역할을 하는 것으로 확인하였다. 확인된 결과를 토대로 문제점을 개선하기 위한 실질적인 방법을 제안하였다. 거칠기 측정 방법에서는 카메라 방식의 3D 스캐너를 사용하는 것이 기존의 방법보다 유효한 것으로 확인하였다. 측정간격은 엘리어싱을 막기 위하여 전단강도에 영향을 주는 작은 돌출부의 1/4 이하가 되어야 한다. 거칠기 정량화 면에서는 거칠기 계수를 돌출부의 규모별로 2개의 성분으로 구분하여 전단 모델에 적용하여야 하는 것으로 분석되었다. 이를 위하여 돌출부의 소성파괴 개념에 근거하여 거칠기를 만곡과 요철로 구분할 수 있는 구분 기준을 제시하였으며, 새로운 전단강도 모델을 제안하기 위한 토대를 마련하였다.

• Transactions on Electrical and Electronic Materials
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• 제16권2호
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• pp.99-102
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• 2015

Thin film transistors (TFTs) with amorphous 2 wt% silicon-doped zinc tin oxide (a-2SZTO) channel layer were fabricated using an RF magnetron sputtering system, and the effect of post-annealing treatment time on the structural and electrical properties of a-2SZTO systems was investigated. It is well known that Si can effectively reduce the generation of oxygen vacancies. However, it is interesting to note that prolonged annealing could have a bad effect on the roughness of a-2SZTO systems, since the roughness of a-2SZTO thin films increases in proportion to the thermal annealing treatment time. Thermal annealing can control the electrical characteristics of amorphous oxide semiconductor (AOS) TFTs. It was observed herein that prolonged annealing treatment can cause bumpy roughness, which led to increase of the contact resistance between the electrode and channel. Thus, it was confirmed that deterioration of the electrical characteristics could occur due to prolonged annealing. The longer annealing time also decreased the field effect mobility. The a-2SZTO TFTs annealed at 500℃ for 2 hours displayed the mobility of 2.17 cm²/Vs. As the electrical characteristics of a-2SZTO annealed at a fixed temperature for long periods were deteriorated, careful optimization of the annealing conditions for a-2SZTO, in terms of time, should be carried out to achieve better performance.