• 한국자기학회지
• /
• 제21권6호
• /
• pp.214-218
• /
• 2011

본 연구에서는 DC 마그네트론 스퍼터링을 이용해 MgO 단결정 기판 위에 성장된 Ag/CoFeB 박막의 스퍼터링 조건에 따른 박막 미세구조의 변화를 연구하였다. Ag 박막의 결정성 및 표면 거칠기는 인가전력(sputtering power) 및 증착온도의 변화에 따라 증착온도가 증가하는 경우 (200) 방향의 결정성이 향상되는 것을 확인하였으며, 인가전력이 증가되는 경우 표면 거칠기가 감소하는 것을 확인하였다. 또한 고분해능 TEM(transmission electron microscopy) 및 XRR(X-ray reflectivity) 측정을 통해 MgO 기판 위 Ag층의 켜쌓기 성장 및 MgO 기판과 Ag층 사이에 산화층에 해당하는 계면층이 존재하는 것을 알 수 있었으며, 증착온도의 증가에 따른 Ag의 섬상구조 형성 및 intermixing 효과에 의한 Ag/CoFeB 계면층의 변화 및 자기적 특성의 변화를 연구하였다.

• 한국표면공학회지
• /
• 제54권6호
• /
• pp.302-306
• /
• 2021

SnO₂ 30/Ag 15/SnO₂ 30 nm(SAS) tri-layer films were deposited on the glass substrates with RF and DC magnetron sputtering and then electron beam is irradiated on the surface to investigate the effect of electron bombardment on the opto-electrical performance of the films. electron beam irradiated tri-layer films at 1000 eV show a higher figure of merit of 2.72×10^-3 Ω^-1 than the as deposited films due to a high visible light transmittance of 72.1% and a low sheet resistance of 14.0 Ω/☐, respectively. From the observed results, it is concluded that the post-deposition electron irradiated SnO₂ 30/Ag 15/SnO₂ 30 nm tri-layer films can be used as a substitute for conventional transparent conducting oxide films in various opto-electrical applications.

• 한국표면공학회지
• /
• 제54권2호
• /
• pp.96-101
• /
• 2021

NaNbO₃:Eu³⁺ phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering at a growth temperature of 100 ℃, with subsequent annealing at temperatures of 800, 900, and 1000 ℃. The effects of annealing temperature on the structural, morphological, and optical properties of the thin films were investigated. The NaNbO₃:Eu³⁺ sputtering target was synthesized by a solid-state reaction of raw materials Na₂CO₃, Nb₂O₅, and Eu₂O₃. The X-ray diffraction patterns exhibited that the thin films had two mixed phases of NaNbO₃ and Eu₂O₃. Surface morphologies were investigated by using field emission-scanning electron microscopy and indicated that the grains of the thin film annealed at 1000 ℃ showed irregular shapes with an average size of approximately 300 nm. The excitation spectra of Eu³⁺-doped NaNbO₃ thin film consisted of a strong charge transfer band centered at 304 nm in the range of 240-350 nm and two weak peaks at 395 and 462 nm, respectively, resulting from the ⁷F₀→⁵L₆ and ⁷F₀→⁵H₂ transitions of Eu³⁺ ions. The emission spectra under excitation at 304 nm exhibited an intense red band centered at 614 nm and two weak bands at 592 and 681 nm. As the annealing temperature increased from 800 ℃ to 1000 ℃, the intensities of all the emission bands and the band gap energies gradually increased. These results indicate that the higher annealing temperature enhance the luminescent properties of NaNbO₃:Eu³⁺ thin films.

• Tribology and Lubricants
• /
• 제35권1호
• /
• pp.1-8
• /
• 2019

Demand for plastic gears are increasing in many industries due to their low production cost, light weight, applicability without lubricant, corrosion resistance and high resilience. Despite these benefits, utilizing plastic gears is limited due to their poor material properties. In this work, DLC coating was applied to improve the tribological properties of polyamide66 gear. 0 V, 40 V, and 70 V of negative bias voltages were selected as a deposition parameter in DC magnetron sputtering system. Pin-on-disk experiment was performed in order to investigate the wear characteristics of the gears. The results of the pin-on-disk experiment showed that DLC coated polyamide66 with 40 V of negative bias voltage had the lowest friction coefficient value (0.134) and DLC coated PA66 with 0 V of negative bias voltage showed the best wear resistance ($9.83{\times}10^{-10}mm^3/N{\cdot}mm$) among all the specimens. Based on these results, durability tests were conducted for DLC coated polyamide66 gears with 0 V of negative bias voltage. The tests showed that the temperature of the uncoated polyamide66 gear increased to about $37^{\circ}C$ while the DLC coated gear saturated at about $25^{\circ}C$. Also, the power transmission efficiency of the DLC coated gear increased by about 6% compared to those without coating. Weight loss of the polyamide66 gears were reduced by about 73%.

• 반도체디스플레이기술학회지
• /
• 제17권4호
• /
• pp.66-69
• /
• 2018

This study was researched the electrical properties of semiconductor devices such as ITO, $SiO_2$, $V_2O_5$ thin films. The films of ITO, $SiO_2$, $V_2O_5$ were deposited by the rf magnetron sputtering system with mixed gases of oxygen and argon to generate the plasma. All samples were cleaned before deposition and prepared the metal electrodes to research the current-voltage properties. The electrical characteristics of semiconductors depends on the interface's properties at the junction. There are two kinds of junctions such as ohmic and schottky contacts in the semiconductors. In this study, the ITO thin film was shown the ohmic contact properties as the linear current-voltage curves, and the electrical characteristics of $SiO_2$ and $V_2O_5$ films were shown the non-linear current-voltage curves as the schottky contacts. It was confirmed that the electronic system with schottky contacts enhanced the electronic flow owing to the increment of efficiency and increased the conductivity. The schottky contact was only defined special characteristics at the semiconductor and the interface depletion layer at the junction made the schottky contact which has the effect of leakage current cutoff. Consequently the semiconductor device with shottky contact increased the electronic current flow, in spite of depletion of carriers.

• 한국전기전자재료학회논문지
• /
• 제32권5호
• /
• pp.387-392
• /
• 2019

$Dy^{3+}$ and $Eu^{3+}$-co-doped $La_2MoO_6$ phosphor thin films were deposited on sapphire substrates by radio-frequency magnetron sputtering at various growth temperatures. The phosphor thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrometry. The optical transmittance, absorbance, bandgap, and photoluminescence intensity of the $La_2MoO_6$ phosphor thin films were found to depend on the growth temperature. The XRD patterns demonstrated that all the phosphor thin films, irrespective of growth temperatures, had a tetragonal structure. The phosphor thin film deposited at a growth temperature of $100^{\circ}C$ indicated an average transmittance of 85.3% in the 400~1,100 nm wavelength range and a bandgap energy of 4.31 eV. As the growth temperature increased, the bandgap energy gradually decreased. The emission spectra under ultraviolet excitation at 268 nm exhibited an intense red emission line at 616 nm and a weak emission line at 699 nm due to the $^5D_0{\rightarrow}^7F_2$ and $^5D_0{\rightarrow}^7F_4$ transitions of the $Eu^{3+}$ ions, respectively, and also featured a yellow emission band at 573 nm, resulting from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of the $Dy^{3+}$ ions. The results suggest that $La_2MoO_6$ phosphor thin films can be used as light-emitting layers for inorganic thin film electroluminescent devices.

• 한국전기전자재료학회논문지
• /
• 제32권5호
• /
• pp.376-381
• /
• 2019

In this work, we evaluated the structural, electrical and optical properties of $Ge_8Sb_2Te_{11}$ and Cu-doped $Ge_8Sb_2Te_{11}$ thin films prepared by rf-magnetron reactive sputtering. The 200-nm-thick deposited films were annealed in a range of $100{\sim}400^{\circ}C$ using a furnace in an $N_2$ atmosphere. The amorphous-to-crystalline phase changes of the thin films were investigated by X-ray diffraction (XRD), UV-Vis-IR spectrophotometry, a 4-point probe, and a source meter. A one-step phase transformation from amorphous to face-centered-cubic (fcc) and an increase of the crystallization temperature ($T_c$) was observed in the Cu-doped film, which indicates an enhanced thermal stability in the amorphous state. The difference in the optical energy band gap ($E_{op}$) between the amorphous and crystalline phases was relatively large, approximately 0.38~0.41 eV, which is beneficial for reducing the noise in the memory devices. The sheet resistance($R_s$) of the amorphous phase in the Cu-doped film was about 1.5 orders larger than that in undoped film. A large $R_s$ in the amorphous phase will reduce the programming current in the memory device. An increase of threshold voltage ($V_{th}$) was seen in the Cu-doped film, which implied a high thermal efficiency. This suggests that the Cu-doped $Ge_8Sb_2Te_{11}$ thin film is a good candidate for PRAM.

• 열처리공학회지
• /
• 제32권2호
• /
• pp.74-78
• /
• 2019

$Zn_2SnO_4$ thin films were deposited on quartzs substrates by using radio-frequency magnetron sputtering system. Thermal treatments at various temperatures were performed to evaluate the effect of annealing temperatures on the properties of $Zn_2SnO_4$ thin films. Surface morphologies were examined by using field emission-scanning electron microscopy and showed that sizes of grains were slightly increased and grain boundaries were clear with increasing annealing temperatures. The deposited $Zn_2SnO_4$ thin films on quartzs substrates were amorphous structures and no distinguishable crystallographic changes were observed with variations of annealing temperatures. The optical transmittance was improved with increasing annealing temperatures and was over 90% in the wavelength region between 350 and 1100 nm at the annealing temperature of $600^{\circ}C$. The optical energy bandgaps, which derived from the absorbance of $Zn_2SnO_4$ thin films, were increased from 3.34 eV to 3.43 eV at the annealing temperatures of $450^{\circ}C$ and $600^{\circ}C$, respectively. As the annealing temperature was increased, the electron concentrations were decreased. The electron mobility was decreased and resistivity was increased with increasing annealing temperatures with exception of $450^{\circ}C$. These results indicate that heat treatments at higher annealing temperatures improve the optical and electrical properties of rf-sputtered $Zn_2SnO_4$ thin films.

• 한국세라믹학회지
• /
• 제56권1호
• /
• pp.49-55
• /
• 2019

$Ti_{0.33}Al_{0.67}N/CrN$ nano-multilayers, which are known to have excellent wear resistance, were prepared using an unbalanced magnetron sputter to have various periods of 2-5 nm. $Ti_{0.33}Al_{0.67}N$ had a hexagonal structure in a single layer, but converted to a cubic structure by forming a multilayer with CrN, which has a cubic structure. Thus, $Ti_{0.33}Al_{0.67}N$ formed a superlattice in the multilayer. The $Ti_{0.33}Al_{0.67}/CrN$ multilayer with a period of 2.5 nm greatly exceeded the hardness of the $Ti_{0.33}Al_{0.67}N$ and the CrN single layer, reaching 39 GPa. According to the low angle X-ray diffraction results, the $Ti_{0.33}Al_{0.67}N/CrN$ multilayer maintained its as-coated structure to a temperature as high as $700^{\circ}C$ and exhibited hardness of 30 GPa. The thickness of the oxide layer of the $Ti_{0.33}Al_{0.67}N/CrN$ multilayered coating was less than one-tenth of those of the single layers. Thus, $Ti_{0.33}Al_{0.67}N/CrN$ multilayered coating had hardness and oxidation resistance far superior to those of its constituent single layers.

• 한국결정성장학회지
• /
• 제31권4호
• /
• pp.190-195
• /
• 2021

상온에서 PET 기판 위에 Mn-SnO₂/Ag/Mn-SnO₂ 3중 다층막을 RF/DC 마그네트론 스파터링 방식으로 제조하였다. EMP 시뮬레이션 결과에 따라 Mn-SnO₂의 막 두께는 40 nm, Ag 막 두께는 13 nm로 고정하였다. 550 nm 파장대역에서 측정한 3중막의 투과율은 82.9에서 88.1 % 범위였으며 면저항은 5.9에서 6.9 Ω/☐로 변화하였다. 가장 높은 성능지수(ϕ_TC)는 48.1 × 10^-3 Ω^-1로 나타났다. 곡률반경 4, 5 mm 조건에서 inner 밴딩과 out 밴딩의 굽힘시험을 10,000회 실시한 결과 Mn-SnO₂/Ag/Mn-SnO₂ 3중막의 저항변화율은 약 1.5 %로 탁월한 기계적 유연성을 보였다.