• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.472.1-472.1
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• 2014

현재 Cu(In,Ga)Se2나 Cu2ZnSn(S,Se)4 (CZTSSe)계 박막태양전지의 버퍼층으로 가장 많이 사용되는 물질은 CdS이다. 하지만 Cd의 독성 문제로 인해 사용에 제약이 있고, CdS의 작은 밴드갭(~2.4 eV)으로 인해 단 파장 영역에서 광활성층의 빛 흡수를 저해하는 문제 때문에 새로운 대체 물질을 찾으려는 연구가 많이 이루어지고 있다. 이러한 관점에서, ZnS계 물질은 독성 원소인 Cd을 사용하지 않고, 3.6 eV 정도의 큰 밴드갭을 가지기 때문에, CdS 버퍼층을 대체하기 위한 물질로 관심을 받고 있다. ZnS계 버퍼층을 증착하는 위해 chemical bath deposition (CBD), molecular beam epitaxy (MBE), thermal evaporation, spray pyrolysis, sputtering, elecrtrodepostion 등의 다양한 공정이 사용될 수 있다. 본 연구에서는 상기의 다양한 공정 가운데, 공정 단가가 낮고, 대면적 공정에 용이한 CBD 공정을 이용하여 ZnS계 버퍼층을 증착하는 연구를 수행하였다. 용액의 조성, 농도, 공정 온도, 시간 등을 비롯한 다양한 공정 변수가 ZnS계 박막의 morphology, 조성, 결정성, 광학적 특성 등 다양한 특성에 미치는 영향이 체계적으로 연구되었다. 또한, 상기 ZnS계 버퍼층을 CZTSSe 박막태양전지에 적용하여 CdS를 성공적으로 대체할 수 있음을 확인하였다. 본 연구를 통하여 ZnS계 버퍼층이 향후 친환경적인 박막태양전지 제조에 활용될 수 있는 가능성을 확인할 수 있었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.177-182
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• 2013

Transparent thin film transistors (TTFT) were fabricated on $N^+$ Si wafers. $SiO_2$, $Si_3N_4/SiO_2$ and $Al_2O_3/SiO_2$ grown on the wafers were used as gate insulators. The rf magnetron sputtered zinc tin oxide (ZTO) films were adopted as active layers. $N^+$ Si wafers were wet-oxidized to grow $SiO_2$. $Si_3N_4$ and $Al_2O_3$ films were deposited on the $SiO_2$ by plasma enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD), respectively. The mobility, $I_{on}/I_{off}$ and subthreshold swing (SS) were obtained from the transfer characteristics of TTFTs. The properties of gate insulators were analyzed by comparing the characteristics of TTFTs. The property variation of the ZTO TTFTs with time were observed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.705-711
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• 2000

A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

• Current Photovoltaic Research
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• v.5 no.1
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• pp.20-24
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• 2017

Recently, three-dimensional (3D) light harvesting structures are highly attracted because of their high light harvesting capacity and charge collection efficiencies. In this study, we have fabricated $Cu_2ZnSn(S_xSe_{1-x})_4$ based 3D thin film solar cells on PR patterned Molybdenum (Mo) substrates using photolithography technique. Specifically, Mo patterns were deposited on PR patterned Mo substrates by sputtering and the thin Cu-Zn-Sn stacked layer was deposited over this Mo patterns by sputtering technique. The stacked Zn-Sn-Cu precursor thin films were sulfo-selenized to form CZTSSe pattern. Finally, CZTSSe absorbers were coated with thin CdS layer using chemical bath deposition and ZnO window layer was deposited over CZTSSe/CdS using DC sputtering technique. Fabricated 3-D solar cells were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) analysis, Field-emission scanning electron microscopy (FE-SEM) to study their structural, compositional and morphological properties, respectively. The 3% efficiency is achieved for this kind of solar cell. Further efforts will be carried out to improve the performance of solar cell through various optimizations.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.21-26
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• 2008

We fabricated nano-particles of ZnO, $In_2O_3$ and $SnO_2$ by using the chemical reaction between metal thin films and polyamic acid. The average size and density of these ZnO, $In_2O_3$ and $SnO_2$ nano-particles was approximately 10, 7, and 15 nm, and $2{\times}10^{11},\;6{\times}10^{11},\;2.4{\times}10^{11}cm^{-2}$, respectively. Then, we fabricated nano-floating gate memory (NFGM) devices with ZnO and $In_2O_3$ nano-particles embedded in the devices' polyimide dielectrics and silicon dioxide layers as control and tunnel oxides, respectively. We measured the current-voltage characteristics, endurance properties and retention times of the memory devices using a semiconductor parameter analyzer. In the $In_2O_3$ NFGM, the threshold voltage shift (${\Delta}V_T$) was approximately 5 V at the initial state of programming and erasing operations. However, the memory window rapidly decreased after 1000 s from 5 to 1.5 V. The ${\Delta}V_T$ of the NFGM containing ZnO was approximately 2 V at the initial state, but the memory window decreased after 1000 s from 2 to 0.4 V. These results mean that metal-oxide nano-particles have feasibility to apply NFGM devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.251-251
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• 2011

본 연구에서는 Zr이 도핑 된 ZnSnO (ZZTO) 기반의 물질을 액상공정을 이용하여 합성하고, 박막트랜지스터를 제작하였다. 출발 물질로써 지르코늄 클로라이드 (ZrCl4), 아연 아세테이트 디하이드레이트 ($Zn(CH_3COO)_2{\cdot}2H_3O$), 틴 클로라이드 ($SnCl_2$)를 아연과 주석 프리커서의 비율을 4:7로 고정하고, 지르코늄 프리커서의 몰비를 변형시켜 제작하였다. 제작된 솔루션은 0.25몰의 몰 농도로 고정하였다. 솔벤트로는 2-메톡시에탄올 (2-methoxyethanol)을 사용하였으며, 준비된 솔루션은 $0.2{\mu}m$ 필터를 이용하여 필터링을 실시하였다. Heavily doped p+ Si 기판에 열적 산화법을 이용하여 120 nm 두께의 $SiO_2$를 성장시킨 것을 게이트 및 게이트 절연막으로 이용하였으며, 스핀코팅을 이용하여 ZZTO 박막을 코팅하였다. 코팅 된 기판은 $300^{\circ}C$에서 $500^{\circ}C$ 사이로 2시간 열처리를 실시하였으며, 마지막으로 소오스/드레인을 스퍼터링법으로 Al을 증착하였다. Zr 함량비, 열처리 온도, 제작된 솔루션의 온도에 따른 박막단계를 파악하기 위해 X-ray photoelectron spectroscopy (XPS), thermogravimetry differential thermal analyzer (TG-DTA), X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HR-TEM), Hall-effect measurement, UV-Vis spectroscopy 분석을 실시하였으며, 제작된 소자는 semiconductor analyzer (HP4156C)를 이용하여 측정하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.315-322
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• 2002

A thin film oxide semiconductor micro gas sensor array which shows only 60㎽ of power consumption at an operating temperature of 30$0^{\circ}C$ has been fabricated using microfabrication and rnicrornachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double la! or structure of 0.1${\mu}{\textrm}{m}$ thick Si$_3$N$_4$ and 1${\mu}{\textrm}{m}$ thick phosphosilicate glass(PSG) prepared by low pressure chemical vapor deposition(LPCVD) and atmospheric－pressure chemical-vapor deposition(APCVD), respectively. The sensor way consists of such thin film oxide semiconductor sensing materials as 1wt.％ Pd-doped SnO$_2$, 6wt.% AI$_2$O$_3$-doped ZnO, WO$_3$ and ZnO. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials. Heater Part of the sensor structure has been modified in order to improve the process yield of the sensor, and as a result of modified heater structure improved process yield has been achieved.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.336-336
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• 2013

Zinc oxide (ZnO) based transparent oxide semiconductors have been studied due to their high transmittance and electrical conductivity. Pure ZnO have unstable optical and electrical properties at high temperatures but doped ZnO thin films can have stable optical and electrical properties. In this paper, transparent oxide semiconductors of Y-doped ZnO thin films prepared by sol-gel method. The ionic radius of $Y^{3+}$ (0.90 A) is close to that of $Zn^{2+}$ (0.74 A), which makes Y suitable dopant for ZnO thin films. The Sn-doped ZnO thin films were deposited onto quartz substrates with different atomic percentages of dopant which were Y/Zn = 0, 1, 2, 3, 4, and 5 at.%. These thin films were pre-heated at $150^{\circ}C$ for 10 min and then annealed at $500^{\circ}C$ or 1 h. The structural and optical properties of the Y-doped ZnO thin films were investigated using field-emission scanning electronmicroscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL).

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.110.2-110.2
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• 2012

We reported on antireflective ZnSnO (ZTO)/Ag bilayer and ZTO/Ag/ZTO trilayer source/drain (S/D) electrodes for all-transparent ZTO channel based thin film transistors (TFTs). The ZTO/Ag bilayer is more transparent (83.71%) and effective source/drain (S/D) electrodes for the ZTO channel/Al2O3 gate dielectric/ITO gate electrode/glass structure than ZTO/Ag/ZTO trilayer because the bottom ZTO layer in the trilayer increasea contact resistance between S/D electrodes and ZTO channel layer and reduce the antireflection effect. The ZTO based all-transparent TFTs with ZTO/Ag bilayer S/D electrode showed a saturation mobility of 4.54cm2/Vs and switching property (1.31V/decade) comparable to TTFT with Ag S/D electrodes.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.43-47
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• 2014

NiO-doped hibonite pigments were synthesized by the solid state method to get stabilized blue color pigment in both oxidation and reduction atmospheres. Optimum substitution condition with NiO for hibonite blue pigment was investigated. Experimental results were comparable to those of previous cobalt-minimization studies performed with other phosphate- or oxide-based cobalt-containing ceramic pigments (having olivine ($Co_2SiO_4$), spinel ($CoAl_2O_4$), or with co-doped willemite ($(Co,Zn)_2SiO_4$) structures). Composition was designed varying the NiO molar ratio increasing with $SnO_2$. The optimum substitution content is 0.93 mole NiO with 0.75mole $SnO_2$. The characteristics of the synthesized pigment were analyzed by XRD, Raman spectroscopy, SEM, and UV-vis. Synthesized pigment was applied to a lime-barium glaze with 10 wt% each and fired at an oxidation atmosphere of $1250^{\circ}C/1h$ and a reducing atmosphere $1240^{\circ}C/1h$. Blue color was obtained with $L^*a^*b^*$ values at 43.39, -6.78, -18.20 under a reducing atmosphere and 41.66, -6.36, -14.7 under and oxidation atmosphere, respectively.