• Composites Research
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• 제36권5호
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• pp.349-354
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• 2023

Poly(3-hexylthiophene) (P3HT)는 유기 용매에서 높은 용해도를 가지고 있으면서 상대적으로 쉽게 구할 수 있는 공액 고분자 중 하나이다. 그러나, 전자소자의 활성 소재로써 전기적 특성은 실제로 응용하기에는 부족하므로 추가 개선이 필요하다. 본 연구에서는, 서로 다른 위치 규칙성 (regio-regularity)을 가지는 두 P3HT 고분자 (즉, regioregular (RR) P3HT 및 regio-random (RRa) P3HT)를 혼합하여 혼합 박막의 전하 전달 특성을 크게 향상시킬 수 있음을 보여준다. 두 P3HT 고분자 간 비율을 변화시킴으로써 혼합 박막의 구조적 및 전기적 특성을 체계적으로 조사하였으며, 원자 힘 현미경(AFM), X선 회절(XRD) 및 UV-vis 흡수분광법을 사용하여 혼합 필름의 구조 및 광전자적 특성을 평가하였다. 혼합 박막의 결정성은 RRa-P3HT 함량이 20 wt%로 증가함에 따라 증가하였으며, 이후 80%까지 증가함에 따라 감소하였다. 전하 이동도의 경향성 또한 이와 같았으며, 20 wt%의 RRa-P3HT를 포함하는 혼합 박막의 전하 이동도는 가장 높은 0.029 cm²/V·s로 측정되었고 함량이 80 wt%까지증가함에따라 0.0007 cm²/V·s 로감소하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.409-409
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• 2014

Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

• 한국진공학회지
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• 제21권4호
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• pp.205-211
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• 2012

인듐주석산화막/폴리에틸렌 테레프탈레이트(ITO/PET: indium tin oxide/polyethylene terephthalate) 유연 기판 위에 성장된 산화아연(ZnO) 나노로드(nanorods)를 이용하여 형성된 은(Ag) 입자의 광학적 특성 및 소수성 표면에 대해 조사하였다. 시료를 준비하기 위해 스퍼터링법(sputtering)으로 코팅된 산화아연 씨드층(seed layer)을 이용하여 전기화학증착법(electrochemical deposition)으로 산화아연 나노로드를 성장시킨 후, 열증발증착법(thermal evaporation)을 사용하여 은을 증착하였다. 산화아연 나노로드의 불연속적인 표면 특성 때문에 은이 증착되면서 나노크기를 갖는 입자로 형성되었다. 비교를 위해 같은 조건으로 은을 평평한 ITO/PET에 증착하여 시료를 준비하였으며, 증착되는 은의 양을 조절하기 위해 100초에서 600초까지 열증발증착시간을 변화시켰다. 은 증착시간이 증가할수록 산화아연 나노로드 표면에 형성되는 은 입자의 크기와 양이 증가하였으며, 또한 빛의 흡수율이 가시광 영역에서 크게 증가하는 것을 확인하였다. 이는 은 입자의 국소표면플라즈몬공명(localized surface plasmon resonance)에서 기인된 것으로 짐작한다. 또한 물방울 테스트실험에서 평평한 ITO/PET에 증착된 은에서의 접촉각(contact angle)보다 산화아연 나노로드에 증착된 은 입자에서의 접촉각이 크게 증가함을 보여, 개선된 소수성 표면을 가질 수 있음을 확인하였다. 이러한 광학적 특성과 소수성 표면 결과는 산화아연 나노로드의 기반의 염료감응형 태양전지 또는 자정효과(self-cleaning)를 갖는 표면구조로 유연소자에 유용하게 응용할 수 있을 것으로 기대된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.189-189
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• 2016

Recently, many researchers have shown an increased interest in colloidal quantum dots (QDs) due to their unique physical and optical properties of size control for energy band gap, narrow emission with small full width at half maxima (FWHM), broad spectral photo response from ultraviolet to infrared, and flexible solution processing. QDs can be widely used in the field of optoelectronic and biological applications and, in particular, colloidal QDs based light emitting diodes (QDLEDs) have attracted considerable attention as an emerging technology for next generation displays and solid state lighting. A few methods have been proposed to fabricate white color QDLEDs. However, the fabrication of white color QDLEDs using single QD is very challenging. Recently, hybrid nanocomposites consisting of CdTe/ZnO heterostructures were reported by Zhimin Yuan et al.[1] Here, we demonstrate a novel but facile technique for the synthesis of CdTe/ZnO/G.O(graphene oxide) quasi-core-shell-shell quantum dots that are applied in the white color LED devices. Our best device achieves a maximum luminance of 484.2 cd/m2 and CIE coordinates (0.35, 0.28).

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.5.2-5.2
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• 2009

From 10 years ago, the development of nano-devices endeavored to achieve reconstruction of information technology (IT) and nano technology (NT) industry. Among the many materials for the IT and NT industry, zinc oxide (ZnO) is a very promising candidate material for the research of nano-device development. Nano-structures of ZnO-based materials were grown easily via various methods and it attracts huge attention because of their superior electrical and optical properties for optoelectronic devices. Recently, among the various growth methods, MOCVD has attracted considerable attention because it is suitable process with benefits such as large area growth, vertical alignment, and accurate doping for nano-device fabrication. However, ZnO based nanowires grown by MOCVD process were had the principal problems of 1st interfacial layers between substrate and nanowire, 2nd a broad diameter (about 100 nm), and 3rd high density, and 4th critical evaporation temperature of Zinc precursors. In particular, the growth of high performance nanowire for high efficiency nano-devices must be formed at high temperature growth, but zinc precursors were evaporated at high temperature.These problems should be repaired for materialization of ultra high performance quantum devices with quantum effect. For this reason, we firstly proposed the growth method of vertical aligned slim MgZnO nanowires (< 10 nm) without interfacial layers using self-phase separation by introduced Mg at critical evaporation temperature of Zinc precursors ($500^{\circ}C$). Here, the self-phase separation was reported that MgO-rich and the ZnO-rich phases were spontaneously formed by additionally introduced Mg precursors. In the growth of nanowires, the nanowires were only grown on the wurzite single crystal seeds as ZnO-rich phases with relatively low Mg composition (~36 at %). In this study, we investigated the microstructural behaviors of self-phase separation with increasing the Mg fluxes in the growth of MZO NWs, in order to secure drastic control engineering of density,diameter, and shape of nanowires.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.43.2-43.2
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• 2011

Single-walled carbon nanotubes (SWCNT) are transparent in the visible and show conductivity comparable to copper, and are environmentally stable. SWCNT films have high flexibility, conductivity and transparency approaching that indium tin oxide (ITO), and can be prepared inexpensively without vacuum equipment. Transparent conducting Films (TCF) of SWCNTs has the potential to replace conventional transparent conducting oxides (TCO, e.g. ITO) in a wide variety of optoelectronic devices, energy conversion and photovoltaic industry. However, the sheet resistance of SWCNT films is still higher than ITO films. A decreased in the resistivity of SWCNT-TCFs would be beneficial for such an application. We fabricated SWCNT sheet with $KAuBr_4$ on PET substrate. Arc-discharge SWCNTs were dispersed in deionized water by adding sodum dodecyl sulfate (SDS) as surfactant and sonicated, followed by the centrifugation. The dispersed SWCNT was spray-coated on PET substrate and dried on a hotplate at $100^{\circ}C$. When the spray process was terminated, the TCF was immersed into deionized water to remove the surfactant and then it was dried on hotplate. The TCF film was then treated with AuBr4-, rinsed with deionized water and dried. The surface morphology of TCF was characterized by field emission scanning electron microscopy. The sheet resistance and optical transmission properties of the TCF were measured with a four-point probe method and a UV-visible spectrometry, respectively. $HNO_3$ treated SWCNT films with Au nano-particles have the lowest 61 ${\Omega}$/< sheet resistance in the 80% transmittance. Sheet resistance was decreased due to the increase of the hole concentration at the washed SWCNT surface by p-type doping of $AuBr_4{^-}$.

• 한국안광학회지
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• 제13권3호
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• pp.73-77
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• 2008

목적: 본 논문은 저온열처리로 비결정 또는 결정 ZnO 박막의 UV emission 가능하다는 것이다. 방법: 화학적 용액법을 이용하여 소다-라임-실리카 유리 위에 100, 150, 200, 250 및 $300^{\circ}C$로 열처리하여 비정질 및 나노 결정질 ZnO 박막을 제조하였으며, 박막의 성장 특성 및 광학적 특성을 X-선 회절 분석법, 자외선-가시광선-근적외선 분광법 및 발광분석법을 통하여 분석하였다. 결과: $100^{\circ}C{\sim}200^{\circ}C$에서 60분간 열처리된 박막은 비정질 특성을 나타내고 있었으며, $250^{\circ}C$ 및 $300^{\circ}C$로 열처리된 박막에서는 ZnO 결정상이 나타났다. 비정질 ZnO 박막의 PL분석에 의하면 매우 강한 Near-band-edge emission이 나타났으며, Green emission은 거의 검출되지 않았다. 결론: 앞으로는 저온에서 ZnO 광전자소자를 쉽게 제조할 수 있을 것이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.207.1-207.1
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• 2014

High-mobility and two dimensional conduction at the interface between two band insulators, LaAlO3 (LAO) and SrTiO3 (STO), have attracted considerable research interest for both applications and fundamental understanding. Several groups have reported the photoconductivity of LAO/STO, which give us lots of potential development of optoelectronic applications using the oxide interface. Recently, a giant photo response of Pd nano particles/LAO/STO is observed in UV illumination compared with LAO/STO sample. These phenomena have been suggested that the correlation between the interface and the surface states significantly affect local charge modification and resulting electrical transport. Water and gas adsorption/desorption can alter the band alignment and surface workfunction. Therefore, characterizing and manipulating the electric charges in these materials (electrons and ions) are crucial for investigating the physics of metal oxide. Proposed mechanism do not well explain the experimental data in various ambient and there has been no quantitative work to confirm these mechanism. Here, we have investigated UV photo response in various ambient by performing transport and Kelvin probe force microscopy measurements simultaneously. We found that Pd nano particles on LAO can form Schottky contact, it cause interface carrier density and characteristics of persistence photo conductance depending on gas environment. Our studies will help to improve our understanding on the intriguing physical properties providing an important role in many enhanced light sensing and gas sensing applications as a catalytic material in different kinds of metal oxide systems.

• 한국재료학회지
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• 제27권3호
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• pp.149-154
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• 2017

Transparent conducting oxides (TCOs) were fabricated using solution-based ITO (Sn-doped $In_2O_3$) nanoinks with nanorods at an annealing temperature of $200^{\circ}C$. In order to optimize their transparent conducting performance, ITO nanoinks were composed of ITO nanoparticles alone and the weight ratios of the nanorods to nanoparticles in the ITO nanoinks were adjusted to 0.1, 0.2, and 0.5. As a result, compared to the other TCOs, the ITO TCOs formed by the ITO nanoinks with weight ratio of 0.1 were found to exhibit outstanding transparent conducting performance in terms of sheet resistance (${\sim}102.3{\Omega}/square$) and optical transmittance (~80.2 %) at 550 nm; these excellent properties are due to the enhanced Hall mobility induced by the interconnection of the composite nanorods with the (440) planes of the short lattice distance in the TCOs, in which the presence of the nanorods can serve as a conducting pathway for electrons. Therefore, this resulting material can be proposed as a potential candidate for solution-based TCOs for use in optoelectronic devices requiring large-scale and low-cost processes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.580-580
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• 2012

Heterostructures has unique and important properties, which may be helpful for finding many potential applications in the field of electronic, thermoelectric, and optoelectronic devices. We synthesized CdTe/Te core-shell heterostructures by vapor-solid process at low temperatures using a quartz tube furnace. Two step vapor-solid processes were employed. First, various tellurium structures such as nanowires, nanorods, nanoneedles, microtubes and microrods were synthesized under various deposition conditions. These tellurium nanostructures were then used as substrates in the second step to synthesize the CdTe/Te core-shell heterostructures. Using this method, various sizes, shapes and types of CdTe/Te core-shell structures were fabricated under a range of conditions. These structures were analysed by scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive x-ray spectroscopy. The vapor phase process at low temperatures appears to be an efficient method for producing a variety of Cd/Te hetero-nanostructures. In addition, the hetero-nanostructures can be tailored to the needs of specific applications by deliberately controlling the synthetic parameters.