• 대한치과교정학회지
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• 제51권4호
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• pp.270-281
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• 2021

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al₂O₃), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel-titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al₂O₃, TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel-titanium archwire with Al₂O₃ reduced the coefficients of friction (CoFs) for the bracket-archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al₂O₃ and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket-archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al₂O₃ coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions: Our findings suggest that the CoFs for metal bracket-archwire combinations used in orthodontic treatment can be decreased by coating with Al₂O₃ and TiN thin films.

• 대한금속재료학회지
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• 제47권1호
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• pp.44-49
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• 2009

본 연구에서는 2인치 ITO의 타깃으로 ITO박막을 성장시킨 후 RTA 처리로 인한 전기적, 광학적 특성의 변화를 조사하였으며, RTA 처리된 ITO 박막을 이용하여 플라즈마 응용 사인보드를 제작 및 구동하였다. RTA공정으로 열처리한 ITO는 투과도는 증가하며, 비저항은 감소함을 관찰하였으며, 투과도의 증가는 RTA로 인한 결정성의 증가로 인한 결과이고, 비저항의 감소는 결정성의 증가와 더불어 치환형 주석의 원자수가 증가하였다고 사료된다. ITO를 이용하여 사인보드 제작시 방전cell의 압력은 3-5 Torr가 적당함을 알 수 있었으며, 전극 간격을 조절하여 120 V 정도의 낮은 플라즈마 개시 전압을 갖는 플라즈마 응용 사인보드를 성공적으로 제작 할 수 있었다.

• 한국표면공학회지
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• 제55권2호
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• pp.96-101
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• 2022

The effects of the growth temperature on the structural, optical, and morphological properties of BaWO₄:Sm³⁺ phosphor thin films were investigated. The BaWO₄:Sm³⁺ thin films were grown on quartz substrates at several growth temperatures by radio-frequency magnetron sputtering. All the thin films crystallized in a tetragonal structure with a main BaWO₄ (112) diffraction peak. The 830 nm-thick BaWO₄:Sm³⁺ thin films grown at 300 ℃ exhibited numerous polygon-shaped particles. The excitation spectra of BaWO₄:Sm³⁺ thin films consisted of a broad excitation band in the 200-270 nm with a maximum at 236 nm due to the O^2--Sm³⁺ charge transfer and two small bands peaked at 402 and 463 nm, respectively. Under 236 nm excitation, the BaWO₄:Sm³⁺ thin films showed an intense red emission peak at 641 nm due to the ⁴G_5/2→⁶H_9/2 transition of Sm³⁺, indicating that the Sm³⁺ ions occupied sites of non-inversion symmetry in the BaWO₄ host lattice. The highest emission intensity was observed for the thin film grown at 300 ℃, with a 51.8% transmittance and 5.09 eV bandgap. The average optical transmittance in the wavelength range of 500-1100 nm was increased from 53.2% at 200 ℃ to 60.8% after growing at 400 ℃. These results suggest that 300 ℃ is the optimum temperature for growing redemitting BaWO₄:Sm³⁺ thin films.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.582-587
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• 2023

The effects of the annealing temperature on the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films grown on quartz substrates by radio-frequency magnetron sputtering were investigated. The thin films were annealed at various annealing temperatures for 20 min in a rapid thermal annealer after growing the thin films. The experimental results showed that the annealing temperature has a significant effect on the properties of the SrWO₄:Sm³⁺ thin films. The crystal structure of the as-grown SrWO₄:Sm³⁺ thin films was transformed from amorphous to crystalline after annealing at 800℃. The preferred orientation along (112) plane and a significant increase in average grain size by 820 nm were observed with increasing the annealing temperature. The average optical transmittance in the wavelength range of 500~1,100 nm was decreased from 72.0% at 800℃ to 44.2% at an annealing temperature of 1,000℃, where the highest value in the photoluminescence intensity was obtained. In addition to the red-shift of absorption edge, a higher annealing temperature caused the optical band gap energy of the SrWO₄:Sm³⁺ thin films to fall rapidly. These results suggest that the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films can be controlled by varying annealing temperature.

• 한국정보통신학회논문지
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• 제7권2호
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• pp.255-262
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• 2003

본 논문에서는 FBAR(film bulk acoustic wave resonator) 필터 응용을 위해 Al 하부전극 상에서 RF magnetron sputtering 기술을 이용한 ZnO 박막 증착 및 공정온도가 ZnO 결정성장에 미치는 영향에 대한 연구결과를 발표한다 ZnO 박막의 압전특성은 FBAR 소자의 공진특성을 결정하는 가장 중요한 요소이고 압전성은 증착된 ZnO박막의 c축 우선배향성의 정도에 의해 결정된다는 사실을 고려한다면 ZnO 결정성장에 미치는 공정온도에 관한 연구는 매우 의미 있는 일이다. 본 실험을 통하여 ZnO 박막의 성장특성은 상온에서부터 35$0^{\circ}C$까지의 실험조건에서 c축 우선배향성의 정도에 따라 RF power에 관계없이 온도를 2개의 임계온도에 의해 나눠진 3개의 온도구간으로 구분할 수 있었다. 결과적으로 20$0^{\circ}C$ 이하의 공정온도에서는 주상형 결정립을 가진 c축 우선배향의 ZnO 박막을 얻을 수 있었다. 이렇게 얻은 ZnO박막을 사용하여 FBAR 다층박막 구조를 구현하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.11-11
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• 2008

ZnO has a very large exciton binding energy (60 meV) as well as thermal and chemical stability, which are expected to allow efficient excitonic emission, even at room temperature. ZnO based electronic devices have attracted increasing interest as the backplanes for applications in the next-generation displays, such as active-matrix liquid crystal displays (AMLCDs) and active-matrix organic light emitting diodes (AMOLEDs), and in solid state lighting systems as a substitution for GaN based light emitting diodes (LEDs). Most of these electronic devices employ the electrical behavior of n-type semiconducting active oxides due to the difficulty in obtaining a p-type film with long-term stability and high performance. p-type ZnO films can be produced by substituting group V elements (N, P, and As) for the O sites or group I elements (Li, Na, and K) for Zn sites. However, the achievement of p-type ZnO is a difficult task due to self-compensation induced from intrinsic donor defects, such as O vacancies (Vo) and Zn interstitials ($Zn_i$), or an unintentional extrinsic donor such as H. Phosphorus (P) doped ZnO thin films were grown on c-sapphire substrates by radio frequency magnetron sputtering with various Ar/ $O_2$ gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio with out post-annealing. The P-doped ZnO films grown at a Ar/ $O_2$ ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of $10^{-17}cm^{-3}$ and $2.5cm^2/V{\cdot}s$, respectively. X-ray diffraction showed that the ZnO (0002) peak shifted to lower angle due to the positioning of $p^{3-}$ ions with a smaller ionic radius in the $O^{2-}$ sites. This indicates that a p-type mechanism was due to the substitutional Po. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/n-Si heterojunction LEO showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission.

• 한국전자통신학회논문지
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• 제12권6호
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• pp.1019-1026
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• 2017

$HfO_2$ 박막은 공정압력을 조정함으로써 박막의 질을 향상시켜 그 구조적 특성을 개선시킬 수 있다. 본 연구에서는 RF 마그네트론 스퍼터링 방법을 이용하여 유리 기판 위에 $HfO_2$ 박막을 증착하였으며, 이때의 기저 진공 압력은 $4.5{\times}10^{-6}Pa$ 이하였으며 RF 파워는 100 W, 기판의 온도는 $300^{\circ}C$ 이었다. 해당 박막 증착 공정의 공정 압력은 1 mTorr 에서 15 mTorr 로 변화되었다. 그 후, 해당 박막의 구조적 및 광학적 특성들을 조사하였다. 특히, 1 mTorr 의 공정 압력으로 증착된 $HfO_2$ 박막이 다른 박막들과 비교하여 가장 우수한 특성을 가진 것으로 나타났으며, 이때의 결정립의 크기는 10.27 nm, 표면 거칠기는 1.173 nm, 550 nm 파장에서의 굴절률은 2.0937, 그리고 550 nm 파장에서의 투과율은 84.85 % 의 우수한 특성을 나타내었다. 이러한 결과들을 통해 1 mTorr 의 공정 압력으로 증착된 $HfO_2$ 박막은 투명 전자 소자에 적용하기에 적합함을 알 수 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.77-77
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• 2016

Thin films synthesized by plasma processes have been widely applied in a variety of industrial sectors. The structure control of thin film is one of prime factor in most of these applications. It is well known that the structure of this film is closely associated with plasma parameters and species of plasma which are electrons, ions, radical and neutrals in plasma processes. However the precise control of structure by plasma process is still limited due to inherent complexity, reproducibility and control problems in practical implementation of plasma processing. Therefore the study on the fundamental physical properties that govern the plasmas becomes more crucial for molecular scale control of film structure and corresponding properties for new generation nano scale film materials development and application. The thin films are formed through nucleation and growth stages during thin film depostion. Such stages involve adsorption, surface diffusion, chemical binding and other atomic processes at surfaces. This requires identification, determination and quantification of the surface activity of the species in the plasma. Specifically, the ions and neutrals have kinetic energies ranging from ~ thermal up to tens of eV, which are generated by electron impact of the polyatomic precursor, gas phase reaction, and interactions with the substrate and reactor walls. The present work highlights these aspects for the controlled and low-temperature plasma enhanced chemical vapour disposition (PECVD) of Si-based films like crystalline Si (c-Si), Si-quantum dot, and sputtered crystalline C by the design and control of radicals, plasmas and the deposition energy. Additionally, there is growing demand on the low-temperature deposition process with low hydrogen content by PECVD. The deposition temperature can be reduced significantly by utilizing alternative plasma concepts to lower the reaction activation energy. Evolution in this area continues and has recently produced solutions by increasing the plasma excitation frequency from radio frequency to ultra high frequency (UHF) and in the range of microwave. In this sense, the necessity of dedicated experimental studies, diagnostics and computer modelling of process plasmas to quantify the effect of the unique chemistry and structure of the growing film by radical and plasma control is realized. Different low-temperature PECVD processes using RF, UHF, and RF/UHF hybrid plasmas along with magnetron sputtering plasmas are investigated using numerous diagnostics and film analysis tools. The broad outlook of this work also outlines some of the 'Grand Scientific Challenges' to which significant contributions from plasma nanoscience-related research can be foreseen.

• The Journal of Advanced Prosthodontics
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• 제5권4호
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• pp.402-408
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• 2013

PURPOSE. The aim of this study was to evaluate the surface properties and in vitro bioactivity to osteoblasts of magnesium and magnesium-hydroxyapatite coated titanium. MATERIALS AND METHODS. Themagnesium (Mg) and magnesium-hydroxyapatite (Mg-HA) coatings on titanium (Ti) substrates were prepared by radio frequency (RF) and direct current (DC) magnetron sputtering.The samples were divided into non-coated smooth Ti (Ti-S group), Mg coatinggroup (Ti-Mg group), and Mg-HA coating group (Ti-MgHA group).The surface properties were evaluated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy (AFM). Cell adhesion, cell proliferation and alkaline phosphatase (ALP) activity were evaluated using MC3T3-E1 cells. Reverse transcription polymerase chain reaction (RT-PCR) analysis was performed. RESULTS. Cross-sectional SEM images showed that Mg and Mg-HA depositionson titanium substrates were performed successfully. The surface roughness appeared to be similaramong the three groups. Ti-MgHA and Ti-Mg group had improved cellular responses with regard to the proliferation, alkaline phosphatase (ALP) activity, and bone-associated markers, such as bone sialoprotein (BSP) and osteocalcin (OCN) mRNA compared to those of Ti-S group. However, the differences between Ti-Mg group and Ti-MgHA group were not significant, in spite of the tendency of higher proliferation, ALP activity and BSP expression in Ti-MgHA group. CONCLUSION. Mg and Mg-HAcoatings could stimulate the differentiation into osteoblastic MC3T3-E1 cells, potentially contributing to rapid osseointegration.

• 한국표면공학회지
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• 제56권2호
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• pp.147-151
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• 2023

Transparent ZnO (100 nm thick) and ZnO/Ti/ZnO (ZTZ) films were prepared with radio frequency (RF) and direct current (DC) magnetron sputtering on the glass substrate at room temperature. During the ZTZ film deposition, the thickness of the Ti interlayer was varied, such as 6, 9, 12, and 15 nm, while the thickness of ZnO films was kept at 50 nm to investigate the effect of the Ti interlayer on the crystallization and opto-electrical performance of the films. From the XRD pattern, it is concluded that the 9 nm thick Ti interlayer showed some characteristic peaks of Ti (200) and (220), and the grain size of the ZnO (002) enlarged from 13.32 to 15.28 nm as Ti interlayer thickness increased. In an opto-electrical performance observation, ZnO single-layer films show a figure of merit of 1.4×10^-11 Ω^-1, while ZTZ films with a 9 nm-thick Ti interlayer show a higher figure of merit of 2.0×10^-5 Ω^-1.