• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.41.2-41.2
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• 2011

Display 산업의 확대로 인해 광학적 특성 및 전기적 특성이 우수한 TCO (Transparent conductive oxide) 연구가 활발히 진행되고 있다. 기존에는 ITO가 대부분의 분야에서 이용되었지만 In의 경제적인 단점으로 인해 새로운 대체물로써 ZnO가 떠오르고 있다. ZnO는 전형적인 n-type 반도체이며, wide band gap 물질로써 Al, Ga, B과 같은 3 족 원소를 doping 함으로써 광학적 및 전기적 특성을 향상시킬 수 있다. 최근에는 ZnO의 이온반경과 비슷한 Ga을 도핑한 Ga-doped ZnO 박막에 대한 연구가 활발히 진행되고 있다. 이는 ZnO에 Ga을 도핑함으로써 격자결함을 최소화 시키고 carrier concentration 및 hall mobility를 향상시켜 전기전도도의 향상을 이루기 때문이다. 본 연구에서는 $Ga_2O_3$이 3wt% doping 된 ZnO rotating cylindrical target 을 DC magnetron sputtering 을 이용하여 2 kW의 파워와 70 kHz의 주파수를 고정하고, 증착 온도를 변화시켜 유리 기판 위에 Ga-doped ZnO 박막을 증착 하였다. 증착 시 온도가 Ga-doped ZnO 박막에 미치는 영향을 관찰하기 위해 박막 표면의 조성을 분석하였고, 결정성 및 전기적 특성의 변화를 통해 박막의 특성을 비교 평가하였다. Ga-doped ZnO 박막의 표면과 두께는 SEM (Scanning electron microscope) 분석을 통해 관찰하였고, XRD (X-ray diffractometer) 를 이용하여 결정학적 특성을 확인하였다. 또한 Van der Pauw 방법을 이용한 hall 측정을 통해 resistivity, carrier concentration, hall mobility를 분석하였고, UV-Vis를 이용하여 박막의 투과율을 분석하였으며, 이를 토대로 투명 전도막으로써 Ga-doped ZnO 박막의 응용 가능성을 평가하였다.

• Journal of IKEEE
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• v.20 no.4
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• pp.392-397
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• 2016

In this paper, Characteristics of the ITO thin film deposited were analyzed using DC magnetron sputtering in order to investigate the deposition conditions of ITO thin film for transparent electrode. The experiment conditions were atmospheric pressure from 1 to 3[mTorr] with 1 [mTorr] step, bias electric voltage ranged from 260[V] to 330[V] with 10[V] step. The transmittance, refractive index and surface and cross-sectional shape of the deposited thin film were measured with an UV.-VIS. spectrophotometer, ellipsometer and SEM. Such condition as 1~2[mTorr] and near 300[V] voltage the transmittance was over 90[%] and the refractive index more than 2. Therefore, it was confirmed that the appropriate condition for making a highly transparent conductive electrode.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.100-100
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• 2011

2004년 일본의 Hosono 그룹에 의해 처음 발표된 이래로, amorphous gallium-indium-zinc oxide (a-GIZO) thin film transistors (TFTs)는 높은 이동도와 뛰어난 전기적, 광학적 특성에 의해 큰 주목을 받고 있다. 또한 넓은 밴드갭을 가지므로 가시광 영역에서 투명한 특성을 보이고, 플라스틱 기판 위에서 구부러지는 성질에 의해 플랫 패널 디스플레이나 능동 유기 발광 소자(AM-OLED), 투명 디스플레이에 응용될 뿐만 아니라, 일반적인 Poly-Si TFT에 비해 백플레인의 대면적화에 유리하다는 장점이 있다. 최근에는 Y2O3나 ZrO2 등의 high-k 물질을 gate insulator로 이용하여 높은 캐패시턴스를 유지함과 동시에 낮은 구동 전압과 빠른 스위칭 특성을 가지는 a-GIZO TFT의 연구 결과가 보고되었다. 하지만 투명 디스플레이 소자 제작을 위해 플라스틱이나 유리 기판을 사용할 경우, 기판 특성상 공정 온도에 제약이 따르고(약 $300^{\circ}C$ 이하), 이를 극복하기 위한 부가적인 기술이 필수적이다. 본 연구에서는 p-type Si을 back gate로 하는 Inverted-staggered 구조의 a-GIZO TFT소자를 제작 하였다. p-type Si (100) 기판위에 RF magnetron sputtering을 이용하여 Gate insulator를 증착하고, 같은 방법으로 채널층인 a-GIZO를 70 nm 증착하였다. a-GIZO를 증착하기 위한 sputtering 조건으로는 100W의 RF power와 6 mTorr의 working pressure, 30 sccm Ar 분위기에서 증착하였다. 소스/드레인 전극은 e-beam evaporation을 이용하여 Al을 150 nm 증착하였다. 채널 폭은 80 um 이고, 채널 길이는 각각 20 um, 10 um, 5 um, 2 um이다. 마지막으로 Furnace를 이용하여 N2 분위기에서 $500^{\circ}C$로 30분간 후속 열처리를 실시한 후에, 전기적 특성을 분석하였다.

• Current Photovoltaic Research
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• v.3 no.3
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• pp.101-105
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• 2015

ZnO is gathering great interest for large square optoelectrical devices of flat panel display (FHD) and solar cell as a transparent conductive oxide (TCO). Herewith, Mg and IIIA (Al, In) co-doped ZnO films were prepared on SLG substrate using RF magnetron sputtering system. The effect of variation of atomic weight % of Mg and ZnO have been investigated. The atomic weight % Al and In are of 3% and kept constant throughout. The numbers of samples were prepared according to their different contents, which are $M_{3%}AZO_{94%}$, $M_{4%}AZO_{93%}-(MAZO)$ and $M_{3%}IZO_{94%}$, $M_{4%}IZO_{93%}-(MIZO)$ respectively. A RF power of 225 W and working pressure of 6 m Torr was used for the deposition at $300^{\circ}C$. All of the two thin film show good uniformity in field emission scanning electron microscopy image. $M_{3%}AZO_{94%}$ thin film shows overall better performance among the all. The film shows the best lowest resistivity, carrier concentration, mobility and Sheet resistance and is found to be are of $8.16{\times}10^{-4}{\Omega}cm$, $4.372{\times}10^{20}/cm^3$, $17.5cm^2/vs$ and $8.9{\Omega}/sq$ respectively. Also $M_{3%}AZO_{94%}$ thin film shows the relatively high optical band gap energy of 3.7 eV with high transmittance more than 80% in visible region required for the better solar cell performance.

• Laser Solutions
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• v.17 no.1
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• pp.1-6
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• 2014

Indium tin oxide (ITO) is an important transparent conducting oxide (TCO). ITO films have been widely used as transparent electrodes in optoelectronic devices such as organic light-emitting devices (OLED) because of their high electrical conductivity and high transmission in the visible wavelength. Finding ways to control ITO micromachining depth is important role in the fabrication and assembly of display field. This study presented the depth control of ITO patterns on glass substrate using a femtosecond laser and slit. In the proposed approach, a gaussian beam was transformed into a quasi-flat top beam by slit. In addition, pattern of square type shaped by slit were fabricated on the surfaces of ITO films using femtosecond laser pulse irradiation, under 1030nm, single pulse. Using femtosecond laser and slit, we selectively controlled forming depth and removed the ITO thin films with thickness 145nm on glass substrates. In particular, we studied the effect of pulse number on the ablation of ITO. Clean removal of the ITO layer was observed when the 6 pulse number at $2.8TW/cm^2$. Furthermore, the morphologies and fabricated depth were characterized using a optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.2
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• pp.75-79
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• 2017

Honeycomb-shaped Ag-grid transparent conductive electrodes (TCEs) were fabricated using two different processes, high density plasma etching and lift-off, and the optical and electrical properties were compared according to the fabrication method. For the fabrication of the Ag-grid TCEs by plasma etching, etch characteristics of the Ag thin film in $10CF_4/5Ar$ inductively coupled plasma (ICP) discharges were studied. The Ag etch rate increased as the power increased at relatively low ICP source power or rf chuck power conditions, and then decreased at higher powers due to either decrease in $Ar^+$ ion energy or $Ar^+$ ion-assisted removal of the reactive F radicals. The Ag-grid TCEs fabricated by the $10CF_4/5Ar$ ICP etching process showed better grid pattern transfer efficiency without any distortion or breakage in the grid pattern and higher optical transmittance values of average 83.3 % (pixel size $30{\mu}m/line$ width $5{\mu}m$) and 71 % (pixel size $26{\mu}m/line$ width $8{\mu}m$) in the visible range of spectrum, respectively. On the other hand, the Ag-grid TCEs fabricated by the lift-off process showed lower sheet resistance values of $2.163{\Omega}/{\square}$ (pixel size $26{\mu}m/line$ width $18{\mu}m$) and $4.932{\Omega}/{\square}$ (pixel size $30{\mu}m/line$ width $5{\mu}m$), respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.110-115
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• 2010

Transparent conducting gallium-doped zinc oxide (GZO) thin films which were deposited on Corning glass substrate using an Gun-type rf magnetron sputtering deposition technology. The GZO thin films were fabricated with an GZO ceramic target (Zn : 97[wt%], $Ga_2O_3$ : 3[wt%]). The GZO thin films were deposited by varying the growth conditions such as the substrate temperature, oxygen pressure. Among the GZO thin films fabricated in this study, the one formed at conditions of the substrate temperature of 200[$^{\circ}C$], Ar flow rate of 50[sccm], $O_2$ flow rate of 5[sccm], rf power of 80[W] and working pressure of 5[mtorr] showed the best properties of an electrical resistivity of $2.536{\times}10^{-4}[{\Omega}{\cdot}cm]$, a carrier concentration of $7.746{\times}10^{20}[cm^{-3}]$, and a carrier mobility of 31.77[$cm^2/V{\cdot}S$], which indicates that it could be used as a transparent electrode for thin film transistor and flat panel display applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.256-261
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• 2009

Hydrophilic and transparent $TiO_2$ thin film was fabricated by sol-gel method and the properties of contact angle, surface morphology, and transmittance were measured. In addition, surfactant Tween 80 was used for increasing the hydrophilic property of thin film. When the contents of Tween 80 in $TiO_2$ solution was 0, 10, 30, 50wt%, the contact angles of $TiO_2$ thin film were $41.4^{\circ}$, $18.2^{\circ}$, $16.0^{\circ}$, $13.2^{\circ}$, respectively. Fabricated $TiO_2$ thin film showed the photocatalytic property that decomposed methylene blue and decreased the absorbance of solution after UV irradiation. $TiO_2$ thin films fabricated with the solution of 30 wt% Tween 80 were deposited on glass (bare), antimony tin oxide (ATO), fluorine tin oxide (FTO), indium tin oxide (ITO) coated glass substrates, and the contact angle and transmittance of thin film was measured. The contact angles of thin films deposited on four substrates were $16.2\sim27.1^{\circ}$ and was decreased to the range of $13.2\sim17.6^{\circ}$ after UV irradiation, Especially, the thin films coated on ATO and FTO glass substrate showed high transmittance of 74.6% in visible range, respectively, and low transmittance of 54.2% and 40.4% in infrared range, respectively.

• Clean Technology
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• v.18 no.1
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• pp.69-75
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• 2012

In this study, we executed an environmental impact assessment about recycling of ITO (Indium Tin Oxide), used for touch panel. ITO is mainly used to make transparent conductive coatings for touch and flat screen LCD (Liquid Crystal Display), ELD (Emitting Light Device), PDP (Plasma Display Panel). This demand is increasing little by little. but form current status, ITO is discarded than recycling. It is important to recycling ITO for national strategies about resource conservation, and reduce environmental burden. Also Landfill or incineration of ITO cloud be harmful to the human health in the long-term. Material Life Cycle Assessment method (MLCA) was conducted for comparison landfill and recycling of ITO. MLCA would provide more information for environmental issues and potential environmental impacts of ITO. The study includes two scenarios, the basic scenario is recycling of ITO (10, 20, 30%) and the other scenario is landfill of ITO. In addition, amount of carbon dioxide and energy were calculated.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.169-169
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• 2010

As display industry requires various applications for future display technology, which can guarantees high level of flexibility and transparency on display panel, oxide semiconductor materials are regarded as one of the best candidates. $InGaZnO_4$(IGZO) has gathered much attention as a post-transition metal oxide used in active layer in thin-film transistor. Due to its high mobility fabricated at low temperature fabrication process, which is proper for application to display backplanes and use in flexible and/or transparent electronics. Electrical performance of amorphous oxide semiconductors depends on the resistance of the interface between source/drain metal contact and active layer. It is also affected by sheet resistance on IGZO thin film. Controlling contact/sheet resistance has been a hot issue for improving electrical properties of AOS(Amorphous oxide semiconductor). To overcome this problem, post-annealing has been introduced. In other words, through post-annealing process, saturation mobility, on/off ratio, drain current of the device all increase. In this research, we studied on the relation between device's resistance and post-annealing temperature. So far as many post-annealing effects have been reported, this research especially analyzed the change of electrical properties by increasing post-annealing temperature. We fabricated 6 main samples. After a-IGZO deposition, Samples were post-annealed in 5 different temperatures; as-deposited, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$ and $500^{\circ}C$. Metal deposition was done on these samples by using Mo through E-beam evaporation. For analysis, three analysis methods were used; IV-characteristics by probe station, surface roughness by AFM, metal oxidation by FE-SEM. Experimental results say that contact resistance increased because of the metal oxidation on metal contact and rough surface of a-IGZO layer. we can suggest some of the possible solutions to overcome resistance effect for the improvement of TFT electrical performances.