排序方式: 共有19条查询结果,搜索用时 31 毫秒
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Ferroelectrically Gated Atomically Thin Transition‐Metal Dichalcogenides as Nonvolatile Memory 下载免费PDF全文
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Han Li Ying Qin Byeongkwan Ko Dipesh B. Trivedi Debarati Hajra Mohammed Yasir Sayyad Lei Liu Sang-Heon Shim Houlong Zhuang Sefaattin Tongay 《Advanced materials (Deerfield Beach, Fla.)》2020,32(33):2002401
Newly discovered 2D Janus transition metal dichalcogenides layers have gained much attention from a theory perspective owing to their unique atomic structure and exotic materials properties, but little to no experimental data are available on these materials. Here, experimental and theoretical studies establish the vibrational and optical behavior of 2D Janus S–W–Se and S–Mo–Se monolayers under high pressures for the first time. Chemical vapor deposition (CVD)-grown classical transition metal dichalcogenides (TMD) monolayers are first transferred onto van der Waals (vdW) mica substrates and converted to 2D Janus sheets by surface plasma technique, and then integrated into a 500 µm size diamond anvil cell for high-pressure studies. The results show that 2D Janus layers do not undergo phase transition up to 15 GPa, and in this pressure regime, their vibrational modes exhibit a nonmonotonic response to the applied pressures (dω/dP). Interestingly, these 2D Janus monolayers exhibit unique blueshift in photoluminescence (PL) upon compression, which is in contrast to many other traditional semiconductor materials. Overall theoretical simulations offer in-depth insights and reveal that the overall optical response is a result of competition between the ab-plane (blueshift) and c-axis (redshift) compression. The overall findings shed the very first light on how 2D Janus monolayers respond under extreme pressures and expand the fundamental understanding of these materials. 相似文献
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High efficiency graphene solar cells by chemical doping 总被引:1,自引:0,他引:1
Miao X Tongay S Petterson MK Berke K Rinzler AG Appleton BR Hebard AF 《Nano letters》2012,12(6):2745-2750
We demonstrate single layer graphene/n-Si Schottky junction solar cells that under AM1.5 illumination exhibit a power conversion efficiency (PCE) of 8.6%. This performance, achieved by doping the graphene with bis(trifluoromethanesulfonyl)amide, exceeds the native (undoped) device performance by a factor of 4.5 and is the highest PCE reported for graphene-based solar cells to date. Current-voltage, capacitance-voltage, and external quantum efficiency measurements show the enhancement to be due to the doping-induced shift in the graphene chemical potential that increases the graphene carrier density (decreasing the cell series resistance) and increases the cell's built-in potential (increasing the open circuit voltage) both of which improve the solar cell fill factor. 相似文献
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Modulating Photoluminescence of Monolayer Molybdenum Disulfide by Metal–Insulator Phase Transition in Active Substrates 下载免费PDF全文
Jiwei Hou Xi Wang Deyi Fu Changhyun Ko Yabin Chen Yufei Sun Sangwook Lee Kevin X. Wang Kaichen Dong Yinghui Sun Sefaattin Tongay Liying Jiao Jie Yao Kai Liu Junqiao Wu 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(29):3976-3984
The atomic thickness and flatness allow properties of 2D semiconductors to be modulated with influence from the substrate. Reversible modulation of these properties requires an “active,” reconfigurable substrate, i.e., a substrate with switchable functionalities that interacts strongly with the 2D overlayer. In this work, the photoluminescence (PL) of monolayer molybdenum disulfide (MoS2) is modulated by interfacing it with a phase transition material, vanadium dioxide (VO2). The MoS2 PL intensity is enhanced by a factor of up to three when the underlying VO2 undergoes the thermally driven phase transition from the insulating to metallic phase. A nonvolatile, reversible way to rewrite the PL pattern is also demonstrated. The enhancement effect is attributed to constructive optical interference when the VO2 turns metallic. This modulation method requires no chemical or mechanical processes, potentially finding applications in new switches and sensors. 相似文献
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Kedi Wu Mark Blei Bin Chen Lei Liu Hui Cai Cassondra Brayfield David Wright Houlong Zhuang Sefaattin Tongay 《Advanced materials (Deerfield Beach, Fla.)》2020,32(17):2000018
Alloying selected layered transitional metal trichalcogenides (TMTCs) with unique chain-like structures offers the opportunities for structural, optical, and electrical engineering thus expands the regime of this class of pseudo-one-dimensional materials. Here, the novel phase transition in anisotropic Nb(1−x)TixS3 alloys is demonstrated for the first time. Results show that Nb(1−x)TixS3 can be fully alloyed across the entire composition range from triclinic-phase NbS3 to monoclinic-phase TiS3. Surprisingly, incorporation of a small concentration of Ti (x ≈ 0.05–0.18) into NbS3 host matrix is sufficient to induce triclinic to monoclinic transition. Theoretical studies suggest that Ti atoms effectively introduce hole doping, thus rapidly decreases the total energy of monoclinic phase and induces the phase transition. When alloyed, crystalline and optical anisotropy are largely preserved as evidenced by high resolution transmission electron microscopy and angle-resolved Raman spectroscopy. Further Raman measurements identify Raman modes to determine crystalline anisotropy direction and offer insights into the degree of anisotropy. Overall results introduce Nb(1−x)TixS3 as a new and easy phase change material and mark the first phase engineering in anisotropic van der Waals (vdW) trichalcogenide systems for their potential applications in two-dimensional superconductivity, electronics, photonics, and information technologies. 相似文献
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Dipesh B. Trivedi Guven Turgut Ying Qin Mohammed Y. Sayyad Debarati Hajra Madeleine Howell Lei Liu Sijie Yang Naim Hossain Patoary Han Li Marko M. Petrić Moritz Meyer Malte Kremser Matteo Barbone Giancarlo Soavi Andreas V. Stier Kai Müller Shize Yang Ivan Sanchez Esqueda Houlong Zhuang Jonathan J. Finley Sefaattin Tongay 《Advanced materials (Deerfield Beach, Fla.)》2020,32(50):2006320
Janus crystals represent an exciting class of 2D materials with different atomic species on their upper and lower facets. Theories have predicted that this symmetry breaking induces an electric field and leads to a wealth of novel properties, such as large Rashba spin–orbit coupling and formation of strongly correlated electronic states. Monolayer MoSSe Janus crystals have been synthesized by two methods, via controlled sulfurization of monolayer MoSe2 and via plasma stripping followed thermal annealing of MoS2. However, the high processing temperatures prevent growth of other Janus materials and their heterostructures. Here, a room-temperature technique for the synthesis of a variety of Janus monolayers with high structural and optical quality is reported. This process involves low-energy reactive radical precursors, which enables selective removal and replacement of the uppermost chalcogen layer, thus transforming classical transition metal dichalcogenides into a Janus structure. The resulting materials show clear mixed character for their excitonic transitions, and more importantly, the presented room-temperature method enables the demonstration of first vertical and lateral heterojunctions of 2D Janus TMDs. The results present significant and pioneering advances in the synthesis of new classes of 2D materials, and pave the way for the creation of heterostructures from 2D Janus layers. 相似文献
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Controlling Structural Anisotropy of Anisotropic 2D Layers in Pseudo‐1D/2D Material Heterojunctions 下载免费PDF全文
Bin Chen Kedi Wu Aslihan Suslu Sijie Yang Hui Cai Aliya Yano Emmanuel Soignard Toshihiro Aoki Katia March Yuxia Shen Sefaattin Tongay 《Advanced materials (Deerfield Beach, Fla.)》2017,29(34)
Chemical vapor deposition and growth dynamics of highly anisotropic 2D lateral heterojunctions between pseudo‐1D ReS2 and isotropic WS2 monolayers are reported for the first time. Constituent ReS2 and WS2 layers have vastly different atomic structure, crystallizing in anisotropic 1T′ and isotropic 2H phases, respectively. Through high‐resolution scanning transmission electron microscopy, electron energy loss spectroscopy, and angle‐resolved Raman spectroscopy, this study is able to provide the very first atomic look at intimate interfaces between these dissimilar 2D materials. Surprisingly, the results reveal that ReS2 lateral heterojunctions to WS2 produce well‐oriented (highly anisotropic) Re‐chains perpendicular to WS2 edges. When vertically stacked, Re‐chains orient themselves along the WS2 zigzag direction, and consequently, Re‐chains exhibit six‐fold rotation, resulting in loss of macroscopic scale anisotropy. The degree of anisotropy of ReS2 on WS2 largely depends on the domain size, and decreases for increasing domain size due to randomization of Re‐chains and formation of ReS2 subdomains. Present work establishes the growth dynamics of atomic junctions between novel anisotropic/isotropic 2D materials, and overall results mark the very first demonstration of control over anisotropy direction, which is a significant leap forward for large‐scale nanomanufacturing of anisotropic systems. 相似文献
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