• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.180-180
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• 2015

Solution processed Resistive random access memory (ReRAM)은 간단한 공정 과정, 고집적도, 저렴한 가격, 대면적화 플라즈마 데미지 최소화 등의 장점으로 차세대 비휘발성 메모리로 써 많은 관심을 받고 있으며, 주로 high-k 물질인 HfOx, TiOx, ZnO 가 이용 된다. IGZO와 ZTO와 같은 산화물 반도체는 높은 이동도, 대면적화, 넓은 밴드갭으로 인하여 투명한 장점으로 LCDs (Liquid crystal displays)에 이용 가능하며, 최근에는 IGZO와 ZTO에서 Resistive Switching (RS) 특성을 확인한 논문이 보고되면서 IGZO와 ZTO를 ReRAM의 switching medium와 TFT의 active material로써 동시에 활용하는 것에 많은 관심을 받고 있다. 이와 같은 산화물 반도체는 flat panel display 회로에 TFT와 ReRAM의 active layer로써 집적가능 하며 systems-on-panels (SOP)에 적용 가능하다. 하지만 IGZO 보다는 ZTO가 In과 Ga을 포함하지 않기 때문에 저렴하다. 그러므로 IGZO를 대신하는 물질로 ZTO가 각광 받고 있다. 본 실험에서는 ZTO film에 Al을 doping하여 메모리 특성을 평가하였다. 실험 방법으로는 p-type Si에 습식산화를 통하여 SiO2를 300 nm 성장시킨 기판을 사용하였다. 그리고 Electron beam evaporator를 이용하여 Ti를 10 nm, Pt를 100 nm 증착 한다. 용액은 Zn와 Tin의 비율을 1:1로 고정한 후 Al의 비율을 0, 0.1, 0.2의 비율로 용액을 각각 제작하였다. 이 용액을 이용하여 Pt 위에 spin coating방법을 이용하여 1000 rpm 10초, 6000 rpm 30초의 조건으로 AZTO (Al-ZnO-Tin-Oxide) 박막을 증착한 뒤, solvent 및 불순물 제거를 위하여 $250^{\circ}C$의 온도로 30분 동안 열처리를 진행하였다. 이후 Electron beam evaporator를 이용하여 top electrode인 Ti를 100 nm 증착하였다. 제작된 메모리의 전기적 특성은 HP 4156B semiconductor parameter analyzer를 이용하여 측정하였다. 측정 결과, AZTO (0:1:1, 0.1:1:1, 0.2:1:1)를 이용하여 제작한 ReRAM에서 RS특성을 얻었으며 104 s이상의 신뢰성 있는 data retention특성을 확인하였다. 그리고 Al의 비율이 증가할수록 on/off ratio가 증가하고 endurance 특성이 향상되는 것을 확인하였다. 결론적으로 Al을 doping함으로써 ZTO film의 메모리 특성을 향상 시켰으며 AZTO film을 메모리와 트랜지스터의 active layer로써 활용 가능할 것으로 기대된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.193-193
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• 2012

In thin film silicon solar cells, p-i-n structure is adopted instead of p/n junction structure as in wafer-based Si solar cells. PECVD is the most widely used thin film deposition process for a-Si:H or ${\mu}c$-Si:H solar cells. Single-chamber PECVD system for a-Si:H solar cell manufacturing has the advantage of lower initial investment and maintenance cost for the equipment. However, in single-chamber PECVD system, doped and intrinsic layers are deposited in one plasma chamber, which inevitably impedes sharp dopant profiles at the interfaces due to the contamination from previous deposition process. The cross-contamination between layers is a serious drawback of single-chamber PECVD system. In this study, a new plasma process to solve the cross-contamination problem in a single-chamber PECVD system was suggested. In order to remove the deposited B inside of the plasma chamber during p-layer deposition, a high RF power was applied right after p-layer deposition with SiH4 gas off, which is then followed by i-layer, n-layer, and Ag top-electrode deposition without vacuum break. In addition to the p-i interface control, various interface control techniques such as FTO-glass pre-annealing in O2 environment to further reduce sheet resistance of FTO-glass, thin layer of TiO2 deposition to prevent H2 plasma reduction of FTO layer, and hydrogen plasma treatment prior to n-layer deposition, etc. were developed. The best initial solar cell efficiency using single-chamber PECVD system of 10.5% for test cell area of 0.2 $cm^2$ could be achieved by adopting various interface control methods.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.1
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• pp.1-7
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• 2024

β-Ga₂O₃ is a material with a wide band gap of ~4.8 eV and a high breakdown-voltage of 8 MV/cm, and is attracting much attention in the field of power device applications. In addition, compared to representative WBG semiconductor materials such as SiC, GaN and Diamond, it has the advantage of enabling single crystal growth with high growth rate and low manufacturing cost [1-4]. In this study, we succeeded in growing a 10 mm thick β-Ga₂O₃ single crystal doped with 0.3 mol% SnO₂ through the EFG (Edge-defined Film-fed Growth) method using multi-slit structure. The growth direction and growth plane were set to [010]/(010), respectively, and the growth speed was about 12 mm/h. The grown β-Ga₂O₃ single crystal was cut into various crystal planes (010, 001, 100, ${\bar{2}}01$) and surface processed. The processed samples were compared for characteristics according to crystal plane through analysis such as XRD, UV/VIS/NIR/Spec., Mercury Probe, AFM and Etching. This research is expected to contribute to the development of power semiconductor technology in high-voltage and high-temperature applications, and selecting a substrate with better characteristics will play an important role in improving device performance and reliability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.857-860
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• 2002

The material that is both conductive in electricity and transparent to the visible-ray is called transparent conducting thin film. It has many field of application such as solar cell, liquid crystal display, transparent electrical heater, selective optical filter, and a optical electric device. In this study, indium tin oxide (ITO ; Sn-doped $In_2O_3$) thin films were deposited on $SiO_2$/soda-lime glass plates by a dc magnetron sputtering technique. The crystallinity and electrical properties of the films were investigated by X-ray diffraction(XRD), atomic force microscopy (AFM) scanning and 4-point probe. The optical transmittance of ITO films in the range of 300-1000nm were measured with a spectrophotometer. As a result, we obtained polycrystalline structured ITO films with (222), (400), and (440) peak. Transmittance of all the films were higher than 90% in the visible range.

• Transactions on Electrical and Electronic Materials
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• v.9 no.4
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• pp.169-172
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• 2008

We attempted to fabricate carbon nanotube field effect transistor (CNT-FET) using single walled carbon nanotube(SWNT) on the heavily doped Si substrate used as a bottom gate, source and drain electrode were fabricated bye-beam lithography on the 500 nm thick $SiO_2$ gate dielectric layer. We investigated electrical and physical properties of this CNT-FET using Scanning Probe Microscope(SPM) and conventional method based on tungsten probe tip technique. The gate length of CNT-FET was 600 nm and the diameter of identified SWNT was about 4 nm. We could observed gating effect and typical p-MOS property from the obtained $V_G-I_{DS}$ curve. The threshold voltage of CNT-FET is about -4.6V and transconductance is 47 nS. In the physical aspect, we could identified SWNT with phase mode of SPM which detecting phase shift by force gradient between cantilever tip and sample surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.295-295
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• 2016

Recently, TCO films with low carrier concentration, high mobility and high work function are proposed beneficial as front electrode in HIT solar cell due to free-carrier absorption in NIR wavelength region and low Schottky barrier height in the front TCO/a-Si:H(p) interface. We report high transmittance and work function zirconium-doped indium tin oxide (ITO:Zr) films with various plasma (Ar/O2 and Ar) conditions. The role of (Ar/O2) plasma was to enhance the work function of the ITO:Zr films whereas the pure Ar plasma based ITO:Zr showed good electrical properties. The RF magnetron sputtered ITO:Zr films with low resistivity and high transmittance were employed as front electrode in HIT solar cells, yield the best performance of 18.15% with an open-circuit voltage of 710 eV and current density of 34.63 mA/cm2. The high work function ITO:Zr films can be used to modify the front barrier height of HIT solar cell.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1248-1251
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• 1995

This paper reports some results of an experimental investigation of planar double injection magnetic sensors. The threshold voltage proved to be very sensitive to an applied magnetic field. The magnitude and direction of the threshold voltage variation depends on the field strength and its orientation with respect to the conduction chennel. The positively-directed field pushes the carriers into the bulk causing an increase in the threhold voltage. These results seem to agree with a path modulation due to Lorentz force. The application of a negative field causes a negative variation, which is dependent on the surface recombination velocity of the silicon-$SiO_2$ interface.

• Transactions on Electrical and Electronic Materials
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• v.15 no.1
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• pp.24-27
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• 2014

In this study, the effects of Mn-doping and the electrode materials on the memory characteristics of $ZnO_xS_{1-x}$ resistive random access memory (ReRAM) devices on plastic are investigated. Compared with the undoped Al/$ZnO_xS_{1-x}$/Au and Al/$ZnO_xS_{1-x}$/Cu devices, the Mn-doped ones show a relatively higher ratio of the high resistance state (HRS) to low resistance state (LRS), and narrower resistance distributions in both states. For the $ZnO_xS_{1-x}$ devices with bottom electrodes of Cu, more stable conducting filament paths are formed near these electrodes, due to the relatively higher affinity of copper to sulfur, compared with the devices with bottom electrodes of Au, so that the distributions of the set and reset voltages get narrower. For the Al/$ZnO_xS_{1-x}$/Cu device, the ratio of the HRS to LRS is above $10^6$, and the memory characteristics are maintained for $10^4$ sec, which values are comparable to those of ReRAM devices on Si or glass substrates.

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.109-113
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• 2004

Zn diffusions in InP have been studied by electrochemical capacitance voltage. The InP layer was grown by metal organic chemical vapor deposition, and $Zn_3P_2$ thin film was deposited on the epitaxial substrates. The samples annealed in a rapid thermal annealing. It is demonstrated that surface hole concentration as high as $1\times10^{19}\textrm{cm}^{-3}$ can be achieved. When the Zn diffusion was carried at $550^{\circ}C$ and 5-20 min., the diffusion depth of hole concentration moves from 1.51$\mu\textrm{m}$ to 3.23 $\mu\textrm{m}$, and the diffusion coeffcient of Zn is $5.4\times10^{-11}\textrm{cm}^2$/sec. After activation, the concentration is two orders higher than that of untreated sample at 0.30 $\mu\textrm{m}$ depth. As the annealing time is increase, the hole concentration remains almost constant, except deep depth. It means that excess Zn interstitials exist in the doped region is rapidly diffusion into the undoped region and convert into substitutional When the thickness of $SiO_2$ thin film is above 1,000$\AA$, the hole concentration becomes stable distribution.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.44-50
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• 2002

Photosynthesis of plants is effective in the range of 550 to 700 nm of the wavelength of solar irradiation. If the conversion of ultraviolet to the above mentioned region is possible, the photosynthesizing ability is expected to be enhanced. $Eu^{3+}$ doped soda-lime bulk and $TiO_2-SiO_2$ sol-gel coated glasses were prepared and their spectroscopic properties were studied. The absorption and emission spectra for the specimens were measured with the changes of wavelength and Eu ion concentration in the range of the wavelength of 300 to 700nm. The transmittance intensity of visible light through the bulk glass and the coated one was unchanged with the addition of Eu element. The emission spectrum intensity of $Eu^{3+}$ was found to be the maximum at 618 nm which is a transition of $^5DO{\rightarrow}^7F_2$. Additionally, it was shown that the intensity was linearly increased up to 10% of the Eu concentration.