• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.11-11
• /
• 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.

• Journal of the Korean Society for Heat Treatment
• /
• v.26 no.6
• /
• pp.288-292
• /
• 2013

We have considered the influence of electron irradiation energy of 300, 600 and 900 eV on the stuctural, electrical and optical properties of GZO/$TiO_2$ thin films prepared with RF magentron sputtering. The optical transmittance and electrical resistivity of the films were dependent on the electron's irradiation energy. The electron irradiated GZO/$TiO_2$ films at 900 eV are grown as a hexagonal wurtzite phase and the resistivity is decreased with electron irradiation energy. The GZO/$TiO_2$ films irradiated at 900 eV shows the lowest resistivity of $4.3{\times}10^{-3}{\Omega}cm$. The optical transmittance in a visible wave length region also increased with the electron irradiation energy. The film that electron irradiated at 900 eV shows 82% of optical transmittance and higher work function of 5.18 eV in this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.137-137
• /
• 2009

Thin-film transistors (TFTs) that can be prepared at low temperatures have attracted much attention due to the great potential for flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited by low field effect mobility or rapidly degraded after exposing to air in many cases. Another approach is amorphous oxide semiconductors. Amorphous oxide semiconductors (AOSs) have exactly attracted considerable attention because AOSs were fabricated at room temperature and used lots of application such as flexible display, electronic paper, large solar cells. Among the various AOSs, a-IGZO was considerable material because it has high mobility and uniform surface and good transparent. The high mobility is attributed to the result of the overlap of spherical s-orbital of the heavy pest-transition metal cations. This study is demonstrated the effect of thickness channel layer from 30nm to 200nm. when the thickness was increased, turn on voltage and subthreshold swing were decreased. a-IGZO TFTs have used a shadow mask to deposit channel and source/drain(S/D). a-IGZO were deposited on SiO2 wafer by rf magnetron sputtering. using power is 150W, working pressure is 3m Torr, and an O2/Ar(2/28 SCCM) atmosphere at room temperature. The electrodes were formed with Electron-beam evaporated Ti(30nm) and Au(70nm) structure. Finally, Al(150nm) as a gate metal was evaporated. TFT devices were heat treated in a furnace at $250^{\circ}C$ in nitrogen atmosphere for an hour. The electrical properties of the TFTs were measured using a probe-station to measure I-V characteristic. TFT whose thickness was 150nm exhibits a good subthreshold swing(S) of 0.72 V/decade and high on-off ratio of 1E+08. Field effect mobility, saturation effect mobility, and threshold voltage were evaluated 7.2, 5.8, 8V respectively.

• Korean Journal of Optics and Photonics
• /
• v.28 no.1
• /
• pp.28-32
• /
• 2017

In this research, we designed an LSPR sensor based on a thin-film multilayer comprising $TiO_2$ and $SiO_2$. The thickness of the overall substrate layer of the suggested multilayer LSPR sensor is limited to 100 nm, and the number of repeating $TiO_2$ and $SiO_2$ thin films is 1-4 within a limited thickness. Additionally, a nanowire structure with a gold thin film of 40 nm, height of 40 nm, period of 600 nm, and line width of 300 nm was formed on the multilayer. To design the variable wavelength-type SPR, the angle was fixed at $75^{\circ}$ and the wavelength was changed. We then simulated the system with the finite-element method (FEM) using Maxwell's equations. It was confirmed that the resonance wavelength became shorter as the number of multilayers increased when the refractive index was fixed. We found that the wavelength changes were more sensitive. However, no changes were observed when the number of the multilayers was three or higher.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.156-156
• /
• 2003

수평 전기로에서 ZnIn$_2$S$_4$ 다결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 2nIn2S4단결정 박막을 반절연성 GaAs(100)기판 위에 성장시켰다. ZnIn2S4 단결정 박막은 증발원의 온도를 610 $^{\circ}C$, 기판의 온도를 450 $^{\circ}C$로 성장시켰고 성장 속도는 0.5 $\mu\textrm{m}$/hr로 확인되었다. ZrIn2S4 단결정 박막의 결정성의 조사에서 10 K에서 광발광(photoluminescence) 스펙트럼이 433 nm (2.8633eV)에서 exciton emission스펙트럼이 가장 강하게 나타났으며, 또한 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 133 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 8.51$\times$$10^{17}$ electron/$cm^{-3}$ 291 $\textrm{cm}^2$/v-s였다. ZnIn2S4 단결정 박막의 광전류 단파장대 봉우리들로부터 10 K에서 측정된 $\Delta$Cr(crystal field splitting)은 0.1678 eV, $\Delta$So(spin orbit coupling)는 0.0148 eV였다. 10 K의 광발광 측정으로부터 고품질의 결정에서 볼 수 있는 free exciton 과 매우 강한 세기의 중성 주개 bound exciton등의 피크가 관찰되었다. 이때 중성 주개 bound exciton의 반치폭과 결합 에너지는 각각 9 meV와 26 meV 였다. 또한 Haynes rule에 의해 구한 불순물의 활성화 에너지는 130 meV 였다.다.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.62 no.4
• /
• pp.223-226
• /
• 2013

In this study, we investigated the electro-optical(EO) characteristic of fringe-field switching(FFS) mode cell by the two kinds of ultraviolet(UV) alignment method on the organic thin film(polyimide: PI). The suitable organic layersfor FFS cell and the aligning capabilities of nematic liquid crystal(NLC) using the in-situ photoalignment method were studied Disclination is observed after conventional photoalignment method for 1h, and in-situ photoalignment method for 1h. Monodomain alignment of the NLC can be observed via in-situ photoalignment method for 2h and 3h. It is considered that NLC alignment is due to photo-depolymerization of the polymer with oblique non-polarized UV irradiation on PI surface. An unstable V-T curve of UV-aligned FFS-LCD with conventional photoalignment method can be achieved. However, a stable V-T curve of UV-aligned FFS-LCD with in-situ photoalignment method(1h), and V-T curve of UV-aligned FFS-LCD with in-situphotoalignment method was much stable comparing with that of other UV-aligned FFS-LCD's. As a result, more stable EO performanceof UV-aligned FFS-LCD with in-situphotoalignment method for 3h is obtained than that of the other UV-aligned FFS-LCD's.

• Journal of Sensor Science and Technology
• /
• v.9 no.1
• /
• pp.36-43
• /
• 2000

In oder to enhance the selectivity of TMA(trimethylamine) gas, the ZnO-based films which were doped with $Al_2O_3$, $TiO_2, $In_2O_3$ and $V_2O_5$ catalysts with various weight percents were deposited in oxygen by RF magnetron sputtering method. To improve electrical stability of sensors, the ZnO-based films were annealed in oxygen at $700^{\circ}C$ for 1 hour. The TMA selectivity of sensors was defined by the magnitude($S_{TMA}/S_{DMA}$ and $S_{TMA}/S_{NH3}$) of TMA sensitivity relative to DMA and sensitivity ammonia($NH_3$) sensitivity, respectively. The $ZnO+Al_2O_3(4\;wt.%)+TiO_2(1\;wt.%)+In_2O_3(1\;wt.%)$ sensor showed high $S_{TMA}/S_{DMA}$ of 5.9 and $S_{TMA}/S_{NH3}$ of 26 to 160 ppm at the working temperature of $300^{\circ}C$ respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.1
• /
• pp.36-43
• /
• 2000

The sulfur pressure and TRA(rapid thermal annealing) conditions of the fabricated SrS:CuCl TFEL devices were optimized to improve blue color luminance. The thickness of the phosphor layer of SrS:CuCl TFEL devices fabricated by electron beam deposition system was 6000 ~ 8000 ${\AA}$. The fabricated TFEL devices were annealed at 800 $^{\circ}C$ for 3 min. It was shown that the crystallinity of SrS:CuCl phosphor was improved by an increase in RTA temperature and RTA time. Blue color was emitted from the TFEL device with emission peak wavelength of 468 nm and 500 nm. The CIE color coordinates were x = 0.21, y = 0.33. The luminance($L_{40}$) of TFEL device strongly depended on the sulfur pressure of deposition chamber and increased from 262 cd/$m^2$ to 728 cd/m2 as the sulfur pressure increased from $8{\times}10^{-6}$ torr to $2{\times}10^{-5}$ torr.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.153-156
• /
• 2004

A newly developed flexible active-matrix (AM-) electrophoretic display (EPD) is reported. The AM-EPD features: (1) low-temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology, (2) fully integrated scan- and data-drivers, (3) flexibility and light-weight realized by transferring the whole circuits onto a plastic substrate using $SUFTLA^{TM}$ (Surface Free Technology by Laser Annealing/Ablation) process. A large storage capacitor is formed in each pixel so that driving electric field can be kept sufficiently strong during a writing period Two-phase driving scheme, a reset-phase which erases a previous image and a writing-phase for writing a new image, was chosen to cope with EPD's high driving voltage. The flexible AM-EPD has been successfully operated with a driving voltage of 8.5 V.

• Journal of Information Display
• /
• v.12 no.4
• /
• pp.213-217
• /
• 2011

Printing technologies were applied to fabricate a flexible organic thin-film transistor (OTFT) backplane for electrophoretic displays (EPDs). Various printing processes were adopted to maximize the figures of each layer of OTFT: screen printing combined with reverse offset printing for the gate electrodes and scan bus lines with Ag ink, inkjet for the source/drain electrodes with glycerol-doped Poly (3,4-ethylenedioxythiophene): Poly (styrenesulfonate) (PEDOT:PSS), inkjet for the semiconductor layer with Triisopropylsilylethynyl (TIPS)-pentacene, and screen printing for the pixel electrodes with Ag paste. A mobility of $0.44cm^2/V$ s was obtained, with an average standard deviation of 20%, from the 36 OTFTs taken from different backplane locations, which indicates high uniformity. An EPD laminated on an OTFT backplane with $190{\times}152$ pixels on an 8-in panel was successfully operated by displaying some patterns.