• 제목/요약/키워드: PHOSPHOR

검색결과 1,149건 처리시간 0.031초

증착 온도가 라디오파 마그네트론 스퍼터링으로 성장한 SnO2:Eu3+ 박막의 특성에 미치는 영향 (Effects of deposition temperature on the properties of SnO2:Eu3+ thin films grown by radio-frequency magnetron sputtering)

  • 조신호
    • 한국표면공학회지
    • /
    • 제56권3호
    • /
    • pp.201-207
    • /
    • 2023
  • Eu3+-doped SnO2 (SnO2:Eu3+) phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering. The deposition temperature was varied from 100 to 400 ℃. The X-ray diffraction patterns showed that all the thin films had two mixed phases of SnO2 and Eu2Sn2O7. The 880 nmthick SnO2:Eu3+ thin film grown at 100 ℃ exhibited numerous pebble-shaped particles. The excitation spectra of SnO2:Eu3+ thin films consisted of a strong and broad peak at 312 nm in the vicinity from 250 to 350 nm owing to the O2--Eu3+ charge transfer band, irrespective of deposition temperature. Upon 312 nm excitation, the SnO2:Eu3+ thin films showed a main emission peak at 592 nm arising from the 5D07F1 transition and a weak 615 nm red band originating from the 5D07F2 transition of Eu3+. As the deposition temperature increased, the emission intensities of two bands increased rapidly, approached a maximum at 100 ℃, and then decreased slowly at 400 ℃. The thin film deposited at 200 ℃ exhibited a band gap energy of 3.81 eV and an average transmittance of 73.7% in the wavelength range of 500-1100 nm. These results indicate that the luminescent intensity of SnO2:Eu3+ thin films can be controlled by changing the deposition temperature.

Cytokine Inductions and Intracellular Signal Profiles by Stimulation of dsRNA and SEB in the Macrophages and Epithelial Cells

  • Jun-Pyo Choi;Purevsuren Losol;Ghazal Ayoub;Mihong Ji;Sae-Hoon Kim;Sang-Heon Cho;Yoon-Seok Chang
    • IMMUNE NETWORK
    • /
    • 제22권2호
    • /
    • pp.15.1-15.16
    • /
    • 2022
  • Foreign molecules, including viruses and bacteria-derived toxins, can also induce airway inflammation. However, to the best of our knowledge, the roles of these molecules in the development of airway inflammation have not been fully elucidated. Herein, we investigated the precise role and synergistic effect of virus-mimicking double-stranded RNA (dsRNA) and staphylococcal enterotoxin B (SEB) in macrophages and epithelial cells. To identify cytokine expression profiles, both the THP-1-derived macrophages and BEAS-2B epithelial cells were stimulated with dsRNA or SEB. A total of 21 cytokines were evaluated in the culture supernatants. We observed that stimulation with dsRNA induced cytokine production in both cell types. However, cytokine production was not induced in SEB-stimulated epithelial cells, compared to the macrophages. The synergistic effect of dsRNA and SEB was evaluated observing cytokine level and intracellular phospho-signaling. Fifteen different types were detected in high-dose dsRNA-stimulated epithelial cells, and 12 distinct types were detected in macrophages; those found in macrophages lacked interferon production compared to the epithelial cells. Notably, a synergistic effect of cytokine induction by co-stimulation of dsRNA and SEB was observed mainly in epithelial cells, via activation of most intracellular phosphor-signaling. However, macrophages only showed an accumulative effect. This study showed that the type and severity of cytokine productions from the epithelium or macrophages could be affected by different intensities and a combination of dsRNA and SEB. Further studies with this approach may improve our understanding of the development and exacerbation of airway inflammation and asthma.

Efficient Red-Color Emission of InGaN/GaN Double Hetero-Structure Formed on Nano-Pyramid Structure

  • 고영호;김제형;공수현;김주성;김택;조용훈
    • 한국진공학회:학술대회논문집
    • /
    • 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
    • /
    • pp.174-175
    • /
    • 2012
  • (In, Ga) N-based III-nitride semiconductor materials have been viewed as the most promising materials for the applications of blue and green light emitting devices such as light-emitting diodes (LEDs) and laser diodes. Although the InGaN alloy can have wide range of visible wavelength by changing the In composition, it is very hard to grow high quality epilayers of In-rich InGaN because of the thermal instability as well as the large lattice and thermal mismatches. In order to avoid phase separation of InGaN, various kinds of structures of InGaN have been studied. If high-quality In-rich InGaN/GaN multiple quantum well (MQW) structures are available, it is expected to achieve highly efficient phosphor-free white LEDs. In this study, we proposed a novel InGaN double hetero-structure grown on GaN nano-pyramids to generate broad-band red-color emission with high quantum efficiency. In this work, we systematically studied the optical properties of the InGaN pyramid structures. The nano-sized hexagonal pyramid structures were grown on the n-type GaN template by metalorganic chemical vapor deposition. SiNx mask was formed on the n-type GaN template with uniformly patterned circle pattern by laser holography. GaN pyramid structures were selectively grown on the opening area of mask by lateral over-growth followed by growth of InGaN/GaN double hetero-structure. The bird's eye-view scanning electron microscope (SEM) image shows that uniform hexagonal pyramid structures are well arranged. We showed that the pyramid structures have high crystal quality and the thickness of InGaN is varied along the height of pyramids via transmission electron microscope. Because the InGaN/GaN double hetero-structure was grown on the nano-pyramid GaN and on the planar GaN, simultaneously, we investigated the comparative study of the optical properties. Photoluminescence (PL) spectra of nano-pyramid sample and planar sample measured at 10 K. Although the growth condition were exactly the same for two samples, the nano-pyramid sample have much lower energy emission centered at 615 nm, compared to 438 nm for planar sample. Moreover, nano-pyramid sample shows broad-band spectrum, which is originate from structural properties of nano-pyramid structure. To study thermal activation energy and potential fluctuation, we measured PL with changing temperature from 10 K to 300 K. We also measured PL with changing the excitation power from 48 ${\mu}W$ to 48 mW. We can discriminate the origin of the broad-band spectra from the defect-related yellow luminescence of GaN by carrying out PL excitation experiments. The nano-pyramid structure provided highly efficient broad-band red-color emission for the future applications of phosphor-free white LEDs.

  • PDF

LiF:Mg,Cu,P 열형광선량계의 선량특성을 이용한 눈가림법에 의한 출력선량 평가 (Evaluation the Output Dose of Linear Accelerator Photon Beams by Blind Test with Dose Characteristics of LiF:Mg,Cu,P TLD)

  • 최태진;이호준;예지원;오영기;김진희;김옥배
    • 한국의학물리학회지:의학물리
    • /
    • 제20권4호
    • /
    • pp.308-316
    • /
    • 2009
  • 조사면의 크기와 한계 측정부위의 선량평가에는 형체가 자유로운 열형광분말체를 이용하는 것이 적합함을 뒷받침하기 위하여 LiF:Mg,Cu,P TLD 분말체의 선량특성을 조사하고, 작성된 평가 알고리즘에 따라 선형가속기의 출력선량을 눈가림법으로 조사한 TLD에 적용했을 때 평가 신뢰성을 확인하고자 한다. 열형광분말소자는 PTW 사의 LiF:Mg,Cu,P (200 Mesh)이며, 판독기는 LTM (LTM Co, France)이다. 물의 흡수선량은 전리함과 전위계를 표준선량평가기관에서 교정한 흡수선량계수를 사용하여 구하였으며, TLD 조사는 자체 제작한 미니 프라스틱 수조의 중앙에 삽입하여 조사면 $10{\times}10\;cm^2$로 시행 하였다. 방사선조사는 두 대학병원에 설치된 선형가속기(Oncor, Siemens와 Clinac Ix, Varian)의 6 MV 광자선으로 하였으며, TLD의 눈가림법 선량평가는 glow 곡선의 특성과 분말질량에 의한 감도변화, 선량률의존성, 선량-TL 강도의 비례성과 퇴행성 조사를 통해 시행되었다. LiF:Mg,Cu,P TLD는 3개의 glow peak를 보였고 232도에 나타나는 peak는 선량과 비례성이 높고 감도가 높으며 퇴행현상이 적어 선량계로써 좋은 조건을 보이고 있다. 열형광선량분말체는 1,000 cGy까지 대략적인 선형관계를 유지하였으나, 정밀 측정평가를 위해 비선형 함수를 통해 평균 1% 오차범위에서 평가할 수 있었다. LiF:Mg,Cu,P TLD는 선량률 22.2 cGy/min에서 600 cGy/min까지 TL 감도에 거의 영향을 주지 않았으나, 가열판(Planchette)의 분말체의 량에 따라서는 TL 감도에 변화가 있음을 확인하였다. 눈가림법으로 두 기관의 선형가속기에서 15회와 10회 조사하였고, 선량범위는 15~800 cGy였다. 눈가림법에 의한 양 기관의 TL 선량은 평균 1% 이하의 오차범위에서 일치하고 편차는 각각 ${\pm}1.9%$${\pm}2.58$ 이내에 있었다. 열형광분말소자를 사용하여 눈가림법으로 출력선량을 평가한 결과 실험오차범위에서 표준전리함의 선량과 잘 일치하였으며, 전리함으로 접근할 수 없는 작은 조사면이나 경계성 조사면에 대한 선량평가에 신뢰성 있는 평가를 할 수 있을 것으로 생각한다.

  • PDF

디지털 방사선사진술을 이용한 치아색 수복물의 방사선불투과도 비교 (RADIOPACITY COMPARISON OF TOOTH COLORED RESTORATIVE MATERIALS WITH DIGITAL RADIOGRAPHY)

  • 김효정;김성교
    • Restorative Dentistry and Endodontics
    • /
    • 제25권4호
    • /
    • pp.499-508
    • /
    • 2000
  • 본 연구에서는 이종의 디지털 방사선사진술이 수복물의 방사선불투과성 비교에 적절하게 이용될 수 있는지의 여부를 평가하고, 이 기법을 이용하여 수종의 compomer 및 유동성 레진의 방사선불투과도를 측정, 비교하고자 하였다. Aluminum step wedge를 방사선사진촬영 하여 기 존의 transmission densitometer와 CD-Dent (phosphor scanning system) 및 RVG$^{(R)}$ (CCD system) 등 두 종류의 디지털 방사선사진술과의 광학밀도 상관관계를 평가하였고, 두께 2mm, 지름 5mm인 원형의 금속주형을 이용하여 Dyract$^{(R)}$ AP, Compoglass$^{(R)}$ 및 Dyract flow$^{(R)}$ 등 3종의 compomer와 Ultraseal-XT$^{(R)}$ plus$^{TM}$, Revolution$^{TM}$, Aeliteflo$^{TM}$ 및 Tetric-flow$^{(R)}$ 등 4종의 유동성 레진의 시편을 각각 5개씩 제작후 방사선불투과성을 측정하고 비교, 평가하여 다음과 같은 결과를 얻었다. 1. Aluminum step wedge를 사용한 광학밀도 측정곡선을 비교한 바, 통상적인 방사선사진술로 얻은 필름의 상에서 transmission densitometer로 방사선불투과도를 측정 한 곡선과 CD-Dent 및 RVG$^{(R)}$ 등 디지털 방사선사진술로 얻은 상에서 CADIA로 불투과도를 측정한 곡선들 사이에서 각각 매우 높은 역상관관계가 나타났다(${\gamma}$=-0.95, ${\gamma}$=-0.98 ; p<0.05). 2. 모든 수복채 공히 상아질과 유사하거나 높은 방사선불투과도를 나타내었고 (p<0.05), compomer인 Dyract$^{(R)}$ AP와 Compoglass$^{(R)}$, 그리고 유동성 레진인 Tetric-flow$^{(R)}$는 통상적인 방사선사진술 및 2종의 디지털 방사선사진술에서 공히 유동성 레진인 Revolution$^{TM}$과 Aeliteflo$^{TM}$, 그리고 상아질에 비해 유의하게 높은 방사선불투과도를 나타내었다 (p<0.05). 3. Compomer인 Dyract$^{(R)}$ AP와 Compoglass$^{(R)}$, 그리고 유동성 레진인 Tetric-flow$^{(R)}$는 통상적인 방사선사진술 및 CD-Dent 디지털 방사선사진술에서 공히 법랑질에 비해 높은 방사선불투과도를 나타내었고(p<0.05), compomer인 Dyract flow$^{(R)}$는 통상적인 방사선사진술에서만 법랑질에 비해 높은 방사선불투과도를 나타내었다(p<0.05).

  • PDF

Carbon nanotube field emission display

  • Chil, Won-Bong;Kim, Jong-Min
    • E2M - 전기 전자와 첨단 소재
    • /
    • 제12권7호
    • /
    • pp.7-11
    • /
    • 1999
  • Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).

  • PDF

녹색 발광의 $CaZrO_3:\;HO_{3+}$ 축광성 형광체의 합성 및 발광 특성 (Synthesis and luminescent properties of a new green $CaZrO_3:\;HO_{3+}$ long persistent phosphors)

  • 박병석;최종건
    • 한국결정성장학회지
    • /
    • 제18권3호
    • /
    • pp.109-114
    • /
    • 2008
  • 새로운 녹색의 $CaZrO_3$ : $HO_{3+}$ 축광성 형광체를 고온의 약한 환원 분위기에서 전통적인 고상 반응법으로 합성하였다. $CaZrO_3$ : $HO_{3+}$ 축광성 형광체에 첨가 된 융제 $H_3BO_3$의 역할과 부활제의 적정농도에 대하여 연구하였으며, 합성한 축광성 형광체의 형광 분석 및 광 발광 분석을 행하였다. 고온의 질소 분위기에서 합성한 $CaZrO_3$ : $HO_{3+}$ 축광성 형광체는 546nm의 발광 피크가 나타남을 확인 하였으며, 장잔광 스펙트럼 또한 폭이 좁은 546 nm의 발광 피크가 나타남에 따라 순수한 녹색의 발광색을 띄고 있음을 확인하였다 녹색의 $CaZrO_3$ : $HO_{3+}$ 축광성 형광체의 발광 지속시간은 254 nm UV lamp로 여기 시킨 후 어두운 곳에서 5시간 이상 발광이 유지되었다. 발광 피크는 $HO_{3+}$ 이온의 $^5F_4$, $^5S_2{\to}^5I_3$ 전이에 의한 것이며, 잔광 특성은 $CaZrO_3$ 격자 내에 trap center가 생성됨 의하여 발생되는 것으로 판단된다.

Stuffed tridymite계 $SrAl_2$$O_4$ : $Eu^{2+}$ 형광체의 발광 및 장잔광특성에 미치는 $Dy_2$$O_3$의 영향 (Effects of $Dy_2$$O_3$ composition for the photoluminescence and long-phosphorescent characteristics of stuffed tridymite $SrAl_2$$O_4$ : $Eu^{2+}$ phosphors)

  • 이영기;김병규
    • 한국결정성장학회지
    • /
    • 제11권2호
    • /
    • pp.71-77
    • /
    • 2001
  • 고상반응법에 의해 제조된 $SrAl_2$$O_4$ : $Eu^{2+}$,$Dy^{3+}$ 계 형광체에 $Dy_2$$O_3$의 농도를 0.0~9.5mol%까지 변화시켜, $Dy_2$$O_3$의 첨가량에 따른 결정특성과 장잔광 축광재료로서 가장 중요한 발광 및 장잔광 특성을 조사하였다. $SrAl_2$$O_4$ : $Eu^{2+}$,$Dy^{3+}$ 계 형광체는 $Dy_2$$O_3$의 농도에 관계없이 녹색의 520nm파장을 최대 발광파장으로 하는 발광스펙트럼을 나타내었고, 발광특성을 크게 저해하지 않는 $SrAl_2$$O_4$의 단일상을 얻기 위한 농도는 1.0mol%이하가 적절하였다. 또한 $SrAl_2$$O_4$ : $Eu^{2+}$,$Dy^{3+}$ 형광체의 잔광 강도는 $Dy_2$$O_3$의 농도에 무관하게 시간에 따라 모든 시료에서 지수 함수적으로 감소하나, $Dy_2$$O_3$의 농도가 1.0mol% 이하인 경우에 발광의 감쇠속도가 작은 뛰어난 장잔광특성을 나타내었다.

  • PDF

X선 검출기를 위해 특수용매 액상법으로 합성한 Gd2O3:Eu의 Europium(Eu) 함량에 따른 입자특성과 발광특성의 분석 (The particle properties and luminescence properties of Gd2O3:Eu using solution-combustion with various Eu content were analysis)

  • 김성현;김영빈;정숙희;김민우;오경민;박지군
    • 한국방사선학회논문지
    • /
    • 제2권3호
    • /
    • pp.11-18
    • /
    • 2008
  • 이 연구에서는 알코올과 증류수를 특정비율로 혼합한 특수용매를 사용하여 합성한 Gd2O3:Eu 나노 분말이 Europium(Eu)함량에 따라 어떤 입자특성과 발광특성을 가지게 되는지에 대하여 조사하였다. 액상법에 사용된 이 용매는 Gadolinium(Gd)과 Europium(Eu)의 용해되는 시간을 현저히 줄임으로써, 실험시간이 단축됨을 확인하였다. 이번 실험에서 Gd2O3:Eu 나노 powder 형광체의 입자특성은 SEM(scanning electron microscope)과 EDX(Energy Dispersive X-ray)를 사용하였으며, 나노 powder의 발광특성은 PL(Photoluminescence), CL(CathodeLuminescence)을 사용하여 측정하였다. 결정들은 30nm~40nm의 크기의 결정을 가졌고 발광특성은 약 620nm의 특정 파장에서 크게 반응함을 알 수 있었으며, Europium(Eu)함량이 1wt%에서 3wt%, 5wt%로 늘어날수록 Photon의 count가 증가하게 되어 발광효율이 증가함을 알 수 있었다.

  • PDF

Study of Localized Surface Plasmon Polariton Effect on Radiative Decay Rate of InGaN/GaN Pyramid Structures

  • Gong, Su-Hyun;Ko, Young-Ho;Kim, Je-Hyung;Jin, Li-Hua;Kim, Joo-Sung;Kim, Taek;Cho, Yong-Hoon
    • 한국진공학회:학술대회논문집
    • /
    • 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
    • /
    • pp.184-184
    • /
    • 2012
  • Recently, InGaN/GaN multi-quantum well grown on GaN pyramid structures have attracted much attention due to their hybrid characteristics of quantum well, quantum wire, and quantum dot. This gives us broad band emission which will be useful for phosphor-free white light emitting diode. On the other hand, by using quantum dot emission on top of the pyramid, site selective single photon source could be realized. However, these structures still have several limitations for the single photon source. For instance, the quantum efficiency of quantum dot emission should be improved further. As detection systems have limited numerical aperture, collection efficiency is also important issue. It has been known that micro-cavities can be utilized to modify the radiative decay rate and to control the radiation pattern of quantum dot. Researchers have also been interested in nano-cavities using localized surface plasmon. Although the plasmonic cavities have small quality factor due to high loss of metal, it could have small mode volume because plasmonic wavelength is much smaller than the wavelength in the dielectric cavities. In this work, we used localized surface plasmon to improve efficiency of InGaN qunatum dot as a single photon emitter. We could easily get the localized surface plasmon mode after deposit the metal thin film because lnGaN/GaN multi quantum well has the pyramidal geometry. With numerical simulation (i.e., Finite Difference Time Domain method), we observed highly enhanced decay rate and modified radiation pattern. To confirm these localized surface plasmon effect experimentally, we deposited metal thin films on InGaN/GaN pyramid structures using e-beam deposition. Then, photoluminescence and time-resolved photoluminescence were carried out to measure the improvement of radiative decay rate (Purcell factor). By carrying out cathodoluminescence (CL) experiments, spatial-resolved CL images could also be obtained. As we mentioned before, collection efficiency is also important issue to make an efficient single photon emitter. To confirm the radiation pattern of quantum dot, Fourier optics system was used to capture the angular property of emission. We believe that highly focused localized surface plasmon around site-selective InGaN quantum dot could be a feasible single photon emitter.

  • PDF