• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.110-110
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• 2010

현재 박막 트랜지스터는 비정질 실리콘 기반의 개발이 주를 이루고 있으며, 이 비정질 실리콘은 성막공정이 간단하고 대면적에 용이하지만 전기적인 특성이 우수하지 않기 때문에 디스플레이의 적용에 어려움을 겪고 있다. 이에 따라 poly-Si을 이용한 박막 트랜지스터의 연구가 진행되고 있는데, 이는 공정온도가 높고, 대면적에의 응용이 어렵다. 따라서 앞으로 저온 공정이 가능하며 대면적 응용이 용이한 박막 트랜지스터의 연구가 필수적이다. 한편 최근 박막 트랜지스터의 채널층으로 사용되는 물질에는 oxide 기반의 ZnO, SnO2, In2O3 등이 주로 사용되고 있고, 보다 적합한 채널층을 찾기 위한 연구가 많이 진행되어 왔다. 최근 Hosono 연구팀에서 IGZO를 채널층으로 사용하여 high mobility, 우수한 on/off ratio의 특성을 가진 소자 제작에 성공함으로써 이를 시작으로 IGZO의 연구 또한 세계적으로 활발한 연구가 이루어지고 있다. 특히, ZnO는 wide band gap (3.37eV)을 가지고 있어 적외선 및 가시광선의 투과율이 좋고, 전기 전도성과 플라즈마에 대한 내구성이 우수하며, 낮은 온도에서도 성막이 가능하다는 특징을 가지고 있다. 그러나 intrinsic ZnO 박막은 bias stress 같은 외부 환경이 변했을 경우 전기적인 성질의 변화를 가져올 뿐만 아니라 고온에서의 공정이 불안정하다는 요인을 가지고 있다. ZnO의 전기적인 특성을 개선하기 위해 본 연구에서는 hafnium을 doping한 ZnO을 channel layer로 소자를 제작하고 전기적 특성을 평가하였다. 이를 위해 DC magnetron sputtering을 이용하여 ZnO 기반의 박막 트랜지스터를 제작하였다. Staggered bottom gate 구조로 ITO 물질을 전극으로 사용하였으며, 제작된 소자는 semiconductor analyzer를 이용하여 출력특성과 전이 특성을 평가하였으며, ZnO channel layer 증착시 hafnium이 도핑 되는 양을 조절하여 소자를 제작한 후 intrinsic ZnO의 소자 특성과 비교 분석하였다. 그 결과 hafnium을 doping 시킨 소자의 field effect mobility가 $6.42cm^2/Vs$에서 $3.59cm^2/Vs$로 낮아졌지만, subthreshold swing 측면에서는 1.464V/decade에서 0.581V/decade로 intrinsic ZnO 보다 좋은 특성을 나타냄을 알 수 있었다. 그리고 intrinsic ZnO의 경우 외부환경에 대한 안정성 문제가 대두되고 있는데, hafnium을 도핑한 ZnO의 경우 temperature, bias temperature stability, 경시변화 등의 다양한 조건에서의 안정성이 확보된다면 intrinsic ZnO 박막트랜지스터의 문제점을 해결할 수 있는 물질로 될 것이라고 기대된다.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1249-1251
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• 1998

We have studied the properties of $GaAs_{0.35}P_{0.65}$ epitaxial films on the GaP according to doping of $NH_3$ gas using VPE method by CVD. The efficiency of $GaAs_{0.35}P_{0.65}$ epitaxial films found to be greatly enhanced by the according of nitrogen doping. The diodes were fabricated by means of Zn diffusion into vapor grown $GaAs_{0.35}P_{0.65}$ epitaxial films doped with N and Te. The effects of nitrogen doping on carrier density of epitaxial films, PL wavelength and the power out, forward voltage of diodes are discussed. In the end, The effect of electrical and optical properties is influenced by the deep level and deep level density of nitrogen doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.217-220
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• 1999

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-0 ceramics. The doping elements can be classified into groups depending on their supeconducting characteristics in the Bi -Sr-Ca-Cu -O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.79-79
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• 2009

Samples of Ta-doped in $In_2O_3-ZnO-SnO_2$(IZTO) with a doping level up to 4wt% were sintered at $1600^{\circ}C$ in $O_2$. The crystal phase of the samples was identified by an X-ray diffraction experiment. apparent density and porosity with sintered temperature from $1500^{\circ}C$ to $1640^{\circ}C$ are mesured by archimedes method. For each sample, the specific resistivity was determined. samples of sintered at $1600^{\circ}C$ had the highest density and lowest porousity and The Ta 0.25-wt%-doped IZTO ceramics had the lowest resistivity.

• Journal of the Semiconductor & Display Technology
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• v.6 no.4
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• pp.29-32
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• 2007

Zinc gallate, $ZnGa_2O_4:Mn^{2+}$ co-doped with different concentrations of $Mg^{2+}$ (0.001- 0.5 mol%) was prepared by solid state synthesis method. These compositions were investigated for their photoluminescence and cathodoluminescence properties. The optimized composition $Zn_{0.990}Mg_{0.005}Ga_2O_4:Mn_{0.005}$ shows higher luminescence intensity compared to the parent phosphor. The intense green emission peak was found at 504 nm. The $Mg^{2+}$ doping does not affect much the decay time. It remains <10 ms for these compositions which make them potential candidate for application in TV screens.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.12
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• pp.984-989
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• 2012

We have investigated the structural, electrical and optical properties of Ga-doped ZnO (GZO) thin films prepared by RF magnetron sputtering with laboratory-made ZnO targets containing 1, 3, 5, 7 wt% of $Ga_2O_3$ powder as a doping source. The GZO thin films show the typical crystallographic orientation with c-axis regardless of $Ga_2O_3$ content in the targets. The $3,000{\AA}$ thick GZO thin films with the lowest resistivity of $7{\times}10^{-4}{\Omega}{\cdot}cm$ are obtained by using the GZO ($Ga_2O_3$= 5 wt%) target. Optical transmittance of all films shows higher than 80% at the visible region. The optical energy band gap for GZO films increases as the carrier concentration ($n_e$) in the film increases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.571-575
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• 2014

We synthesized new materials of $Zn(HPB)_2$ and Ir-complexes as blue or red emitting material. We fabricated white Organic Light Emitting Diodes (OLED) by using $Zn(HPB)_2$ for the blue emitting layer, Ir-complexes for the red emitting layer and $Alq_3$ for the green emitting layer. We fabricated white OLED by using double emitting layers of $Zn(HPB)_2$:Ir-complexes and $Alq_3$. The doping rate of Ir-complexes was varied, such as 0.2%, 0.4%, 0.6%, and 0.8%, respectively. When the doping rate of $Zn(HPB)_2$:Ir-complexes was 0.6%, white emission was achieved. The Commission Internationale de l'Eclairage (CIE) coordinates of the white emission was (0.322, 0.312).

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.243.2-243.2
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• 2011

ZnO materials with a wide band gap of approximately 3.3 eV has been used in transparent conducting oxides (TCO) due to exhibitinga high optical transmission, but its low conductivity acts as role of a limitation for conducting applications. Recently, Ga or Al-doped ZnO (GZO, AZO) becomes transparent conducting materials because of high optical transmission and excellent conductivity. However, the fundamental mechanism underlying the improvement of electrical conductivity of the GZO is still the subject of debate. In this study, we have fully investigated the reasons of high conductivity through the characterization of plane defects, crystal orientation, doping contents, crystal structure in Zn1-xGaxO (x=0, 3, 5.1, 5.6, 6.6 wt%). We manufactured Zn1-xGaxO by sintering ZnO and Ga2O3 powers, having a theoretical density of 99.9% and homogeneous Ga-dopant distribution in ZnO grains. The GZO containing 5.6 wt% Ga represents the highest electrical conductivity of $7.5{\times}10^{-4}{\Omega}{\cdot}m$. In particular, many twins and superlattices were induced by doping Ga in ZnO, revealed by X-ray diffraction measurements and TEM (transmission electron microscopy) observations. Twins developed in conventional ZnO crystal are generally formed at (110) and (112) planes, but we have observed the twins at (113) plane only, which is the first report in ZnO material. Interestingly, the superlattice structure was not observed at the grains in which twins are developed and the opposite case was true. This structural change in the GZO resulted in the difference of electrical conductivity. Enhancement of the conductivity was closely related to the extent of Ga ordering in the GZO lattice. Maximum conductivity was obtained at the GZO with a superlattice structure formed ideal ordering of Ga atoms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1023-1028
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• 2004

RF magnetron sputtering을 이용하여 증착한 투명전도성 ZnO 박막의 F 도핑량에 따른 전기, 구조, 광학적 특성에 대해 고찰하였다. 순수 ZnO와 ZnO : $ZnF_2$(1.3 wt%) 그리고 ZnO : $ZnF_2$(10 wt%) 3개의 타겟들을 2개씩 조합 각각의 rf 파워를 조절하여 co-sputtering 방법으로 $ZnF_2$ wt%를 변화시켜 박막내의 F 도핑량을 조절하였다. 증착된 박막들은 열처리에 따른 물성 변화를 분석하기 위해 $5{\times}10^{-7}$ torr 이하의 진공 분위기에서 $300^{\circ}C$에서 2 시간 동안 열처리하였다. XRD 분석 결과 제작된 모든 ZnO 박막은 (002) 우선 방위 특성을 보였고 F 도핑량 증가에 따라 (101), (110), (100) 방향의 약한 피크들이 나타났으며, 이러한 구조적 특성 변화는 이동도의 변화와 밀접한 관계가 있는 것으로 나타났다. Auger로 박막 내의 F 량을 분석한 결과 최대 5.9 at%의 F이 포함되어 있었으며, 열처리 후 캐리어 농도와 이동도는 증가하였고 최고 $37cm^2/Vs$의 이동도를 나타내었으며, 모든 박막들은 가시광 영역에서 81 % 이상의 투과도를 가졌다.

• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.46-50
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• 2017

The Zn1-xMnxO ($0.00{\leq}x{\leq}0.06$) samples have been synthesized in the form of powder by the coprecipitation method at low temperature using $Zn(CH_3COO)_2$. $2H_2O$ and $Mn(CH_3COO)_2$. $4H_2O$ powders, as well as HCl and $NH_4OH$ solutions as starting materials. Characterization was conducted using XRD, TEM, XRF, FTIR and VSM. The result shows that the $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles have the wurtzite phase with a hexagonal structure and particle sizes ranging from 17.48 to 118.83 nm. In a qualitative analysis of XRF, the peaks that confirm the existence of the manganese element in Mn-doped ZnO samples were observed. Meanwhile, FTIR test result shows that there are peaks at around $500cm^{-1}$ and $400cm^{-1}$ in the FTIR spectra for Mn doped ZnO samples which clearly reveal the existence of the (Zn, Mn)-O strain mode. The (Zn, Mn)-O absorption peak positions have shifted to a lower wave number with increasing Mn doping content. The peak intensity is also lower if compared to that of the ZnO sample without doping. From the VSM test, it is shown that $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles are all paramagnetic having monotonically increased susceptibility as increasing Mn content.