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951.
A numerical work has been carried out to study the effect of heated plate on double diffusive natural convection in a cavity with the presence of Soret and Dufour effects. The vertical left and right sidewalls of the cavity are maintained at constant cold temperatures while the lower and upper walls are considered insulated. The influence of pertinent parameters such as Rayleigh number, Schmidt number, vortex viscosity parameter, Soret and Dufour coefficients and plate non-uniformity parameter on the flow and heat transfer characteristics has been examined. Numerical results show that the heat and mass transfer rate increases with the rise of the Rayleigh number and Schmidt number. It is found that the heat and mass transfer rate are considerably suppressed by the vortex viscosity parameter. In addition, it is observed that the average Nusselt number increases and Sherwood number decreases with increasing Soret and Dufour effects. 相似文献
952.
Mobility Engineering in Vertical Field Effect Transistors Based on Van der Waals Heterostructures
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Yong Seon Shin Kiyoung Lee Young Rae Kim Hyangsook Lee I. Min Lee Won Tae Kang Boo Heung Lee Kunnyun Kim Jinseong Heo Seongjun Park Young Hee Lee Woo Jong Yu 《Advanced materials (Deerfield Beach, Fla.)》2018,30(9)
Vertical integration of 2D layered materials to form van der Waals heterostructures (vdWHs) offers new functional electronic and optoelectronic devices. However, the mobility in vertical carrier transport in vdWHs of vertical field‐effect transistor (VFET) is not yet investigated in spite of the importance of mobility for the successful application of VFETs in integrated circuits. Here, the mobility in VFET of vdWHs under different drain biases, gate biases, and metal work functions is first investigated and engineered. The traps in WSe2 are the main source of scattering, which influences the vertical mobility and three distinct transport mechanisms: Ohmic transport, trap‐limited transport, and space‐charge‐limited transport. The vertical mobility in VFET can be improved by suppressing the trap states by raising the Fermi level of WSe2. This is achieved by increasing the injected carrier density by applying a high drain voltage, or decreasing the Schottky barrier at the graphene/WSe2 and metal/WSe2 junctions by applying a gate bias and reducing the metal work function, respectively. Consequently, the mobility in Mn vdWH at +50 V gate voltage is about 76 times higher than the initial mobility of Au vdWH. This work enables further improvements in the VFET for successful application in integrated circuits. 相似文献
953.
Ultrastretchable Conductor Fabricated on Skin‐Like Hydrogel–Elastomer Hybrid Substrates for Skin Electronics
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Sun Hong Kim Sungmook Jung In Seon Yoon Chihak Lee Youngsu Oh Jae‐Min Hong 《Advanced materials (Deerfield Beach, Fla.)》2018,30(26)
Printing technology can be used for manufacturing stretchable electrodes, which represent essential parts of wearable devices requiring relatively high degrees of stretchability and conductivity. In this work, a strategy for fabricating printable and highly stretchable conductors are proposed by transferring printed Ag ink onto stretchable substrates comprising Ecoflex elastomer and tough hydrogel layers using a water‐soluble tape. The elastic modulus of the produced hybrid film is close to that of the hydrogel layer, since the thickness of Ecoflex elastomer film coated on hydrogel is very thin (30 µm). Moreover, the fabricated conductor on hybrid film is stretched up to 1780% strain. The described transfer method is simpler than other techniques utilizing elastomer stamps or sacrificial layers and enables application of printable electronics to the substrates with low elastic moduli (such as hydrogels). The integration of printed electronics with skin‐like low‐modulus substrates can be applied to make wearable devices more comfortable for human skin. 相似文献
954.
Monolithic Flexible Vertical GaN Light‐Emitting Diodes for a Transparent Wireless Brain Optical Stimulator
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Han Eol Lee JeHyuk Choi Seung Hyun Lee Minju Jeong Jung Ho Shin Daniel J. Joe DoHyun Kim Chang Wan Kim Jung Hwan Park Jae Hee Lee Daesoo Kim Chan‐Soo Shin Keon Jae Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(28)
Flexible inorganic‐based micro light‐emitting diodes (µLEDs) are emerging as a significant technology for flexible displays, which is an important area for bilateral visual communication in the upcoming Internet of Things era. Conventional flexible lateral µLEDs have been investigated by several researchers, but still have significant issues of power consumption, thermal stability, lifetime, and light‐extraction efficiency on plastics. Here, high‐performance flexible vertical GaN light‐emitting diodes (LEDs) are demonstrated by silver nanowire networks and monolithic fabrication. Transparent, ultrathin GaN LED arrays adhere to a human fingernail and stably glow without any mechanical deformation. Experimental studies provide outstanding characteristics of the flexible vertical μLEDs (f‐VLEDs) with high optical power (30 mW mm?2), long lifetime (≈12 years), and good thermal/mechanical stability (100 000 bending/unbending cycles). The wireless light‐emitting system on the human skin is successfully realized by transferring the electrical power f‐VLED. Finally, the high‐density GaN f‐VLED arrays are inserted onto a living mouse cortex and operated without significant histological damage of brain. 相似文献
955.
Efficient Hydrogen Evolution Reaction Catalysis in Alkaline Media by All‐in‐One MoS2 with Multifunctional Active Sites
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Mohsin Ali Raza Anjum Hu Young Jeong Min Hee Lee Hyeon Suk Shin Jae Sung Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(20)
MoS2 becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from 1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A‐MoS2) that predominantly comprises 1T‐MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS2 results in the removal of intercalated NH3 and H2S to form an all‐in‐one MoS2 with multifunctional active sites mentioned above (R‐MoS2) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2‐based electrocatalysts. In particular, a hybrid MoS2/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm?2), demonstrating that R‐MoS2‐based materials can potentially replace Pt catalysts in practical alkaline HER systems. 相似文献
956.
Facilitated Water Transport through Graphene Oxide Membranes Functionalized with Aquaporin‐Mimicking Peptides
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Chang Seon Lee Moon‐ki Choi Ye Young Hwang Hyunki Kim Moon Ki Kim Yun Jung Lee 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Water purification by membranes is widely investigated to address concerns related to the scarcity of clean water. Achieving high flux and rejection simultaneously is a difficult challenge using such membranes because these properties are mutually exclusive in common artificial membranes. Nature has developed a method for this task involving water‐channel membrane proteins known as aquaporins. Here, the design and fabrication of graphene oxide (GO)‐based membranes with a surface‐tethered peptide motif designed to mimic the water‐selective filter of natural aquaporins is reported. The short RF8 (RFRFRFRF, where R and F represent arginine and phenylalanine, respectively) octapeptide is a concentrated form of the core component of the Ar/R (aromatic/arginine) water‐selective filter in aquaporin. The resulting GO‐RF8 shows superior flux and high rejection similar to natural aquaporins. Molecular dynamics simulation reveal the unique configuration of RF8 peptides and the transport of water in GO‐RF8 membranes, supporting that RF8 effectively emulates the core function of aquaporins. 相似文献
957.
Duong Nguyen Minh Sangwon Eom Lan Anh Thi Nguyen Juwon Kim Jae Hyun Sim Chunhee Seo Jihye Nam Sangheon Lee Soyeon Suk Jaeyong Kim Youngjong Kang 《Advanced materials (Deerfield Beach, Fla.)》2018,30(39)
Perovskite nanoparticle composite films with capability of high‐resolution patterning (≥2 µm) and excellent resistance to various aqueous and organic solvents are prepared by in situ photosynthesis of acrylate polymers and formamidinium lead halide (FAPbX3) nanoparticles. Both positive‐ and negative‐tone patterns of FAPbX3 nanoparticles are created by controlling the size exclusive flow of nanoparticles in polymer networks. The position of nanoparticles is spatially controlled in both lateral and vertical directions. The composite films show high photoluminescence quantum yield (up to 44%) and broad color tunability in visible region (λpeak = 465–630 nm). 相似文献
958.
Light‐Emitting Diodes: Monolithic Flexible Vertical GaN Light‐Emitting Diodes for a Transparent Wireless Brain Optical Stimulator (Adv. Mater. 28/2018)
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959.
Lithography: Perovskite Nanoparticle Composite Films by Size Exclusion Lithography (Adv. Mater. 39/2018)
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960.
Jun Chen Gang Seob Jung Gyeong Hee Ryu Ren‐Jie Chang Si Zhou Yi Wen Markus J. Buehler Jamie H. Warner 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(42)
It is shown that tilt grain boundaries (GBs) in bilayer 2D crystals of the transition metal dichalcogenide WS2 can be atomically sharp, where top and bottom layer GBs are located within sub‐nanometer distances of each other. This expands the current knowledge of GBs in 2D bilayer crystals, beyond the established large overlapping GB types typically formed in chemical vapor deposition growth, to now include atomically sharp dual bilayer GBs. By using atomic‐resolution annular dark‐field scanning transmission electron microscopy (ADF‐STEM) imaging, different atomic structures in the dual GBs are distinguished considering bilayers with a 3R (AB stacking)/2H (AA′ stacking) interface as well as bilayers with 2H/2H boundaries. An in situ heating holder is used in ADF‐STEM and the GBs are stable to at least 800 °C, with negligible thermally induced reconstructions observed. Normal dislocation cores are seen in one WS2 layer, but the second WS2 layer has different dislocation structures not seen in freestanding monolayers, which have metal‐rich clusters to accommodate the stacking mismatch of the 2H:3R interface. These results reveal the competition between maintaining van der Waals bilayer stacking uniformity and dislocation cores required to stitch tilted bilayer GBs together. 相似文献