• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.6
• /
• pp.1393-1398
• /
• 2015

In this study, the electrical and optical properties of GZO (Ga-doped ZnO) thin films prepared on PES substrates by RF magnetron sputtering method with various working pressures (5 to 20 mTorr) were investigated. All GZO thin films exhibited c-axis preferential growth regardless of working pressure, the GZO thin film deposited at 5 mTorr showed the most excellent crystallinity having 0.44˚ of FWHM. In AFM observations, surface roughness exhibited the lowest value of 0.20 nm in a thin film produced by the working pressure 5 mTorr. Figure of merits of GZO thin film deposited at 5 mTorr showed the highest value of 6652, in this case resistivity and average transmittance in the visible light region were 6.93×10^-4Ω-cm and 81.4%, respectively. We could observed the Burstein-Moss effect that carrier concentration decrease with the increase of working pressure and thus the energy band gap is narrowed.

• Tribology and Lubricants
• /
• v.34 no.4
• /
• pp.146-159
• /
• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.53-58
• /
• 2002

Electrical insulation and mechanical properties of the plasma sprayed oxide ceramic coatings were studied before and after the sealing treatment of the ceramic coatings. Plasma sprayed A1$_2$O$_3$-TiO$_2$ coating as the reference coating was sealed using three commercial sealants based on polymer. Penetration depth of the sealants to the ceramic coating was evaluated directly from the optical microscope using a fluorescent dye. It is estimated that the penetration depth of the sealants to the ceramic coating is from 0.2 to 0.5 mm depending on the sealants used. The preliminary test results with a DC puncture tester imply that the dielectric breakdown voltage mechanism of plasma sprayed ceramic coatings has been determined to be a corona mechanism. Dielectric breakdown voltage of the as-sprayed and as-ground samples have shown a linear trend with regard to the thickness showing an average dielectric strength of 20 kV/mm for the thickness scale studied. It is also shown that grinding the coating before sealing and adding fluorescent dye do not agent the penetration depth of sealants. All of the microhardness, two-body abrasive wear resistance, bond strength, and surface roughness of the ceramic coating after the sealing treatment are improved. The extent of improvement is different from the sealants used. However, three-point bending stress of the ceramic coating after the sealing treatment is decreased. This is attributed to the reduced micro-crack toughening effect since the cracks propagate easily through the lamellar of the coating without crack deflection and/or branching after the sealing treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.3
• /
• pp.318-326
• /
• 1996

This study is to investigate a chemical vapor deposition technique of copper film which is expected to be more useful as metallizations of microcircuit fabrication. An experimental equipment was designed and set-up for this study, and a Cu-precursor used that is a metal-organic compound, named (hfac)Cu(I)VTMS ; (hevaflouoroacetylacetonate trimethyvinylsilane copper). Base pressure of the experimental system is in $10^{-6}$ Torr, and the chamber pressure and the substrate temperature can be controlled in the system. Before the deposition of copper thin film, tungsten or titanium nitride film was deposited onto the silicon wafer. Helium has been used as carrier gas to control the deposition rate. As a result, deposition rate was measured as $1,800\;{\AA}/min$ at $220^{\circ}C$ which is higher than the results of previous studies, and the average surface roughness was measured as about $200\;{\AA}$. A deposition selectivity was observed between W or TiN and $SiO_{2}$ substrates below $250^{\circ}C$, and optimum results are observed at $180^{\circ}C$ of substrate temperature and 0.8 Torr of chamber pressure.

• Tribology and Lubricants
• /
• v.34 no.3
• /
• pp.93-107
• /
• 2018

The purpose of Part I of this study is to find the potential region of wear scarring on engine journal bearings operating at a constant angular crank shaft velocity under firing conditions. To do this, we calculate the applied loads and eccentricities of a big-end journal bearing installed on a four-stroke and four-cylinder engine at every crank angle. Then, we find potential wear regions, such as a minimum oil film thickness, at every crank angle below most oil film thickness scarring wear (MOFTSW) obtained based on the concept of the centerline average surface roughness. Thus, the wear region is defined as a set of each film thickness below the MOFTSW at every crank angle. In this region, the wear volume changes according to the wear depth and wear angle, depending on the minimum oil film thickness at every crank angle. The total wear volume is the summation during one cycle. Graphical views of the region in the two-dimensional coordinates show the crank angle and bearing angle along the journal center path, indicating the position of the minimum oil film thickness. The results of wear analysis show that the possible wear region is located at a few tens of angles behind the upper center of a big-end bearing at maximum power rpm.

• Journal of Korea Water Resources Association
• /
• v.45 no.6
• /
• pp.583-596
• /
• 2012

The revetment is a installed structure on the slope of river bank to protect against flowing. Through the design standards of domestic and overseas, the maximum tractive force is calculated and applied to the average concept on the slope of river bank. In the case of calculating the method of permissible tractive force on the slope of river bank, there is a need to consider soil sliding. In this study, suggested the tractive force formulae by section of adhesion that have 0 < ${\Phi}$ < $90^{\circ}$ slope of river bank and installed an open channel of length of 20 m and 2 m wide for calculating permissible tractive force and hydraulic model experimented with changing discharge. According to the results, the calculated permissible tractive force of section on the slope is the largest due to the significant effects of surface roughness of different revetment materials. In addition, the permissible tractive force increased in the presence of vegetation but has no the effect by vegetation density.

• Nuclear Engineering and Technology
• /
• v.52 no.11
• /
• pp.2585-2593
• /
• 2020

Swift heavy ion (SHI) beam irradiation can generate desirable defects in materials by transferring sufficient energy to the lattice that favours huge possibilities in tailoring of materials. The effect of Ag¹⁵⁺ ion irradiation with energy 200 MeV on spray deposited V₂O₅ thin films of thickness 253 nm is studied at various ion doses from 5 × 10¹¹ to 1 × 10¹³ ions/㎠. The XRD results of pristine film confirmed orthorhombic structure of V₂O₅ and its average crystallite size was found to be 20 nm. The peak at 394 cm^-1 in Raman spectra confirmed O-V-O bonding of V₂O₅, whereas 917 cm^-1 arise because of distortion in stoichiometry by a loss of oxygen atoms. Raman peaks vanished completely above the ion fluence of 5 × 10¹² ions/㎠. Optical studies by UV-Vis spectroscopy shows decrement in transmittance with an increase in ion fluence up to 5 × 10¹² ions/㎠. The red shift is observed both in the direct and indirect band gaps until 5 × 10¹² ions/㎠. The surface topography of the pristine film revealed sheath like structure with randomly distributed spherical nano-particles. The roughness of film decreased and the density of spherical nanoparticles increased upon irradiation. Irradiation improved the conductivity significantly for fluence 5 × 10¹¹ ions/㎠ due to band gap reduction and grain growth.

• Journal of the Semiconductor & Display Technology
• /
• v.10 no.2
• /
• pp.39-44
• /
• 2011

In this study, we have investigated the structural and electrical characteristics of IZO thin films deposited on flexible substrate for the OLED (organic light emitting diodes) devices. For this purpose, PES was used for flexible substrate and IZO thin films were deposited by RF magnetron sputtering under oxygen ambient gases (Ar, $Ar+O_2$) at room temperature. In order to investigate the influences of the oxygen, the flow rate of oxygen in argon mixing gas has been changed from 0.1sccm to 0.5sccm. All the samples show amorphous structure regardless of flow rate. The electrical resistivity of IZO films increased with increasing flow rate of $O_2$ under $Ar+O_2$. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO electrodes made by configuration of IZO/a-NPD/DPVB/$Alq_3$/LiF/Al to elucidate the performance of IZO substrate. OLED devices with the amorphous-IZO (a-IZO) anode film show better current density-voltage-luminance characteristics than that of OLED devices with the commercial crystalline-ITO (c-ITO) anode film. It can be explained that very flat surface roughness and high work function of a-IZO anode film lead to more efficient hole injection by reduction of interface barrier height between anode and organic layers. This suggests that a-IZO film is a promising anode materials substituting conventional c-ITO anode in OLED devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.332-335
• /
• 2004

Boron Phosphide films were deposited on(III) Si substrate at $650^{\circ}C$, by the reaction of $B_2H_6$ with $PH_3$ using CVD. $N_2$ was employed as carrier gas. The optimal gas rates were 20 ml/min for $B_2H_6$, 60 ml/min for $PH_3$ ml/min and $1{\ell}/min$ for $N_2$. The films were annealed for 1hour in $N_2$ ambient at $550^{\circ}C$ and measured. The measurement of AFM shows that the average surface roughness is each $10.108{\AA}$ and $29.626{\AA}$. So, we could know every commonplace thing. The measurement of XRD shows that the films have the preferred orientation of(1 0 1). From SEM images, we could see that Boron Phosphide is showed of a structure, which is grain size, which is grain boundary size. Also, the measurement of AES is shown the films have $B_{13}P_2$ Stoichiometry. From WDX See that ingredient is detected each Boron and Phosporus. So, we could see that deposited BP thin film. In this study, we obtained the BP thin film by deposited in atmosphere pressure, and known to applicate as microwave absorbtion material of BP thin film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.442-443
• /
• 2006

Electrical, optical, surface, and structural properties of amorphous indium zinc oxide (IZO) films grown on $SiO_2$/PES/$SiO_2$ substrate by a RF sputtering in pure Ar ambient at room temperature were investigated. A sheet resistance of $13.5\;{\Omega}{\square}$, average transmittance above 85 % in 550 nm, and root mean square roughness of $10.5\;{\AA}$ were obtained even in the IZO layers grown at room temperature in pure Ar ambient. Without addition of oxygen gas during IZO sputtering process, we can obtain high quality IZO anode films from the specially synthesized oxygen rich IZO target. XRD result shows that the IZO films grown at room temperature is completely amorphous structure due to low substrate temperature. In addition, the electrical and optical properties of the flexible OLED fabricated on IZO/$SiO_2$/PES/$SiO_2$ is critically influenced by the electrical properties of a IZO anode. This findings indicate that the IZO/$SiO_2$/PES/$SiO_2$ is a promising anode/substrate scheme for realizing organic based flexible displays.