• 한국전기전자재료학회논문지
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• 제27권7호
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• pp.472-476
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• 2014

We report the characteristics of thin-film transistor (TFT) to make the bi-channel structure with stacked $Mg_{0.1}Zn_{0.9}O$ (Mg= 10 at.%) and ZnO. The ZnO and $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited by radio frequency (RF) co-sputter system onto the thermally oxidized silicon substrate. A total thickness of active layer was 50 nm. Firstly, the ZnO thin films were deposited to control the thickness from 5 nm to 30 nm. Sequentially, the $Mg_{0.1}ZnO_{0.9}O$ thin films were deposited to change from 45 nm to 20 nm. The bi-layer TFT shows more improved properties than the single layer TFT. The field effect mobility and subthreshold slope for $Mg_{0.1}ZnO_{0.9}O$/ZnO-TFT are $7.40cm^2V^{-1}s^{-1}$ and 0.24 V/decade at the ZnO thickness of 10 nm, respectively.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.3.1-3.1
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• 2011

Over the past decade, the major efforts for lowering the cost of electronics has been devoted to increasing the packaging efficiency of the integrated circuits (ICs), which is defined by the ratio of all devices on system-level board compared to the area of the board, and to working on a larger but cheaper substrates. Especially, in flexible electronics, the latter has been the favorable way along with using novel nanomaterials that have excellent mechanical flexibility and electrical properties as active channel materials and conductive films. Here, the tool for achieving large area patterning is by printing methods. Although diverse printing methods have been investigated to produce highly-aligned structures of the nanomaterials with desired patterns, many require laborious processes that need to be further optimized for practical applications, showing a clear limit to the design of the nanomaterial patterns in a large scale assembly. Here, we demonstrate the alignment of highly ordered and dense silicon (Si) NW arrays to anisotropically etched micro-engraved structures using a simple evaporation process. During evaporation, entropic attraction combined with the internal flow of the NW solution induced the alignment of NWs at the corners of pre-defined structures. The assembly characteristics of the NWs were highly dependent on the polarity of the NW solutions. After complete evaporation, the aligned NW arrays were subsequently transferred onto a flexible substrate with 95% selectivity using a direct gravure printing technique. As proof-of-concept, flexible back-gated NW field effect transistors (FETs) were fabricated. The fabricated FETs had an effective hole mobility of 0.17 $cm2/V{\cdot}s$ and an on/off ratio of ${\sim}1.4{\times}104$. These results demonstrate that our NW gravure printing technique is a simple and effective method that can be used to fabricate high-performance flexible electronics based on inorganic materials.

• 한국재료학회지
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• 제15권3호
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• pp.202-208
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• 2005

The surface states of gate dielectrics affect device performance severely in Pentacene OTFTs. We have fabricated organic thin-film transistors (OTFTs) using pentacene as an active layer with chemically modified $SiO_2$ gate dielectrics. The effects of the surface treatment of $SiO_2$ on the electric characteristics of OTFTS were investigated. The surface of $SiO_2$ gate dielectric was treated by normal wet cleaning process, $O_2-plasma$ treatment, hexamethyldisilazane (HMDS), and octadecyltrichlorosilane (OTS) treatment. After the surface treatments, the contact angles and surface free energies were measured in order to analyze the surface state changes. In the electrical measurements, typical I-V characteristics of TFTs were observed. The field effect mobility, $\mu$, was calculated to be $0.29\;cm^2V^{-1}s^{-1}$ for OTS treated sample while those for the HMDS, $O_2$ plasma treated, and wet-cleaned samples were 0.16, 0.1, and $0.04\;cm^2V^{-1}s^{-1}$, respectively.

• 한국결정학회지
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• 제11권4호
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• pp.212-223
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• 2000

A stochiometric mix of CuInTe₂ polycrystal was prepared in a honizonatal furnace. To obtain the single crystal thin films, CuInTe₂ mixed crystal was deposited on throughly etched GaAs(100) by the HWE system. The source and substrate temperatures were 610℃ and 450℃ respectively, and the thickness of the deposited single crystal thin film was 2.4㎛. CuInTe₂ single crystal thin film was proved to be the optimal growth condition when the excition emission spectrum was the strongest at 1085.3 nm(1.1424 eV) of photoluminescence spectrum at 10 K, and also FWHM of Double Crystal X-ray Rocking Curve (DCRC) was the smallest, 129 arcsec. The Hall effect on this sample was measured by the method of Van der Pauw, and the carrier density and mobility dependent on temperature were 9.57x10/sup 22/ electron/㎥, 1.31x10/sup -2/㎡/V·s at 293 K, respectively. The ΔCr(Crystal field splitting) and the ΔSo (spin orbit coupling splitting( measured at f10K from the photocurrent peaks in the short wavelength of the CuInTe₂ single crystal thin film were about 0.1200 eV, 0.2833 eV respectively. From the PL spectra of CuInTe₂ single crystal thin film at 10 K, the free exciton (E/sub x/) was determined to be 1064.5 nm(1.1647 eV) and the donor-bound exciton(D/sup 0/, X) and acceptor-bound exciton (A/sup 0/, X) were determined to be 1085.3 nm(1.1424 eV) and 1096.8 nm(1.1304 eV0 respectively. And also, the donor-acciptor pair (DAP)P/sub 0/, DAP-replica P₁, DAP-replica P₂ and self-activated (SA) were determined to be 1131 nm (1.0962 eV), 1164 nm(1.0651 eV), 1191.1 nm(1.0340 eV) and 1618.1 nm (0.7662 eV), respectively.

• 한국결정성장학회지
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• 제26권6호
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• pp.232-237
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• 2016

약물의 공결정 형성은 결정구조를 디자인하여 물리적인 성질을 제어하는 방법으로 각광받고 있다. 특히, 밀링 결정화법은 약물 공결정의 형성 여부를 판단하기 위한 스크리닝 기법으로 널리 사용되고 있는데, 대부분의 경우에 소량의 액체를 첨가하는 것이 필요하다. 본 연구에서는 액체의 첨가가 없는 밀링법을 가능하게 하기 위해서, ibuprofen/nicotinamide의 공결정화에 온도가 미치는 영향을 살폈다. 액체질소 냉각 온도와 상온에서의 밀링을 비교하였을 때, 액체질소 냉각 상태에서 공결정화가 상대적으로 효과적으로 진행된 것을 XRD, DSC 등의 분석법을 이용하여 확인하였다. 이러한 결과는 원료 물질의 유리전이 온도 이하에서 밀링하였을 때 분자의 운동성이 제한되어, 원료 결정구조의 파쇄와 공결정 유도가 효과적으로 일어나는 것으로 해석할 수 있다. 본 결과가 약물 밀링 공결정화에 응용되기 위해서는 여러 약물 공결정에 대한 추가 연구가 필요하다.

• Journal of Information Display
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• 제10권1호
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• pp.33-36
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• 2009

A new hybrid silicon thin-film transistor (TFT) fabrication process using the DPSS laser crystallization technique was developed in this study to realize low-temperature poly-Si (LTPS) and a-Si:H TFTs on the same substrate as a backplane of the active-matrix liquid crystal flat-panel display (AMLCD). LTPS TFTs were integrated into the peripheral area of the activematrix LCD panel for the gate driver circuit, and a-Si:H TFTs were used as a switching device of the pixel electrode in the active area. The technology was developed based on the current a-Si:H TFT fabrication process in the bottom-gate, back-channel etch-type configuration. The ion-doping and activation processes, which are required in the conventional LTPS technology, were thus not introduced, and the field effect mobility values of $4\sim5cm^2/V{\cdot}s$ and $0.5cm^2/V{\cdot}s$ for the LTPS and a-Si:H TFTs, respectively, were obtained. The application of this technology was demonstrated on the 14.1" WXGA+(1440$\times$900) AMLCD panel, and a smaller area, lower power consumption, higher reliability, and lower photosensitivity were realized in the gate driver circuit that was fabricated in this process compared with the a-Si:H TFT gate driver integration circuit

• 한국전기전자재료학회논문지
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• 제25권7호
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• pp.531-536
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• 2012

We herein present results of flat and uniform polymer-blended small molecular semiconductor thin films. Which were produced for organic thin film transistors (OTFTs), using a simple pre-metered horizontal dipping process. The organic semiconducting thin films were composed of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) composite blended with a polymer binder of poly(${\alpha}$-methylstyrene) (PaMS). We show that the pre-metered horizontal-dip-coating(H-dip-coating) process allowed the critical control of the thickness of the blended TIPS-PEN:PaMs thin film. The fabricated OTFTs using the TIPS-PEN:PaMs films exhibited maximum field-effect mobility of $0.22\;cm^2\;V^{-1}\;s^{-1}$. These results demonstrated that H-dip-coated TIPS-PEN:PaMS films show considerable promise for the production of reliable, reproducible, and high-performance OTFTs.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권1호
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• pp.13-20
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• 2003

Both MgO and $Sc_2O_3$ are shown to provide low interface state densities (in the $10^{11}{\;}eV^{-1}{\;}cm{\;}^{-2}$ range)on n-and p-GaN, making them useful for gate dielectrics for metal-oxide semiconductor(MOS) devices and also as surface passivation layers to mitigate current collapse in GaN/AlGaN high electron mobility transistors(HEMTs).Clear evidence of inversion has been demonstrated in gate-controlled MOS p-GaN diodes using both types of oxide. Charge pumping measurements on diodes undergoing a high temperature implant activation anneal show a total surface state density of $~3{\;}{\times}{\;}10^{12}{\;}cm^{-2}$. On HEMT structures, both oxides provide effective passivation of surface states and these devices show improved output power. The MgO/GaN structures are also found to be quite radiation-resistant, making them attractive for satellite and terrestrial communication systems requiring a high tolerance to high energy(40MeV) protons.

• 전자공학회논문지D
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• 제36D권11호
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• pp.27-32
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• 1999

고온 열처리 시킨 $LiNbO_3/Si$(100) 구조를 이용한 MFS 디바이스를 제작하여 비휘발성 메모리 동작을 확인하였다. 제작한 트랜지스터의 선형영역에서 산출한 전계효과 이동도와 상호 컨덕턴스는 각각 약 $600cm^2/Vs$ 및 0.16mS/mm 이었다. 0.5V의 게이트 전압(즉, read 전압)에서 측정한 드레인 전류의 온/오프 비는 $10^4$배 이상이었다. 분극반전에 사용한 전압은 ${\pm}3V$ 이하로 매우 낮아 이는 저소비전력용 집적회로에 적용시키기에 기대가 된다. 세게 도핑시킨 반도체위에 제작한 MFS 커패시터는 500kHz의 바이폴라 전압펄스(peak-to-peak 6V, 50% duty cycle) 측정으로 $10^{10}$ cycle 까지도 분극의 열화현상이 없는 양호한 특성을 얻었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.376.1-376.1
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• 2014

그래핀은 차세대 2차원 물질로서 지금까지 활발히 연구되어 왔으나 밴드갭이 없기 때문에 전자소자로서의 응용이 매우 제한적이다. 최근에 그래핀을 대체할 수 있는 물질로서 Transition Metal Dichalcogenides (TMDs)가 주목을 받고 있다. 특히, TMDs 중에서 $MoS_2$는 bulk일 때 indirect한 1.2 eV인 밴드 갭을 갖고 있으나, layer가 줄어들면서 direct한 1.8 eV인 밴드갭을 가진다. 국내외 여러 연구 그룹에서 $MoS_2$를 이용하여 제작한 Field Effect Transistor (FET)는 high-$\small{K}$ gate가 산입되지 않은 경우에 on-off ratio와 mobility가 각각 $10^6$와 약 $3cm^2/Vs$로 나타나고 있다. 이와 같이 아주 우수한 전기적, 광학적 특성을 갖는 소자 응용성을 가지고 있다. 최근까지의 연구결과들은 대부분 mechanical exfoliation method (MEM) 로 제작된 $MoS_2$ monolayer를 이용하였으나, 이 방법은 large scale 및 layer controllable에는 적합하지 않다. 본 연구에서는 대면적의 집적회로 응용에 적합한 chemical vapor deposition법을 이용하여 $MoS_2$를 성장하였다. 높은 결정성을 위해 sulphur (powder purity 99.99%)와 molybdenum trioxide(powder purity 99.9%)를 이용하고, Ar 가스 분위기에서 sulphur powder 및 molybdenum trioxide powder를 각각 $130^{\circ}C$ 및 $1000^{\circ}C$로 유지하며 $MoS_2$ 박막을 성장하였다. 성장된 $MoS_2$ 박막은 Atomic force Microscopy (AFM)을 통해 박막의 단차와 roughness을 확인하였다. 또한, X-ray Diffraction (XRD) pattern 분석으로 박막의 결정성을 확인하였으며, Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Photoluminescence (PL) 측정으로 광학적 특성을 분석하였다.