Molecular simulations have largely contributed to the emergence of Metal Organic Frameworks (MOFs) not only for the resolution of the crystal structures of the most complex and poorly crystallized solids but also to enumerate all the plausible structures constructed by the assembly of a large diversity of inorganic and organic building blocks. Besides this in silico design of novel MOFs which has been only rarely validated so far by the post-synthesis of the desired material, a computational effort has been deployed to modulate the chemical and topological features of existing architectures specifically targeted for societally-relevant applications. Molecular modelling has been also frequently used to guide interpretation of the experimental data by providing a deep understanding of the microscopic adsorption/separation mechanism with the objective to drive the synthesis effort towards tuned materials with the required features for an optimization of their properties. This presentation will highlight the invaluable contribution of the computational approaches from the birth of novel MOFs and their structure elucidations to the characterization and understanding of their properties, throughout recent advances our groups have made in this field. A special emphasizes will be devoted to a series of recent MOFs that show promising adsorption/separation performances for natural gas upgrading, carbon capture and interesting features for mechanical energy storage and proton conduction.
We report the experimental demonstration of an abnormal, opposite anti-crossing effect in a photon-magnon-coupled system that consists of an Yttrium Iron Garnet film and an inverted pattern of split-ring resonator structure (noted as ISRR) in a planar geometry. It is found that the normal shape of anti-crossing dispersion typically observed in photon-magnon coupling is changed to its opposite anti-crossing shape just by changing the position/orientation of the ISRR's split gap with respect to the microstrip line axis along which ac microwave currents are applied. Characteristic features of the opposite anti-crossing dispersion and its linewidth evolution are analyzed with the help of analytical derivations based on electromagnetic interactions. The observed opposite anti-crossing dispersion is ascribed to the compensation of both intrinsic damping and coupling-induced damping in the magnon modes. This compensation is achievable by controlling the relative strength and phase of oscillating magnetic fields generated from the ISRR's split gap and the microstrip feeding line. The position/orientation of an ISRR's split gap provides a robust means of controlling the dispersion shape of anti-crossing and its damping in a photon-magnon coupling, thereby offering more opportunity for advanced designs of microwave devices. a) Correspondence and requests for materials should be addressed to S.-K. K sangkoog@snu.ac.kr
transparent, and wearable electronics and optoelectronics due to their reduced dimensions that offer flexibility and transparency with proper band gap, high carrier mobility, and highly efficient light absorption. [1][2][3] In addition, their ideally dangling-bond-free surface and atomic thickness are promising for ideal heterogeneous contact and reduced short channel effect, [4] thus making them suitable for future nano-scaled electronic and optoelectronic devices. An ideal field-effect transistor based on an molybdenum disulfide (MoS 2 ) channel is theoretically predicted to reach large on/off ratio (>10 9 ), room temperature mobility of 410 cm 2 (Vs) −1 , and near-ideal subthreshold swing of 60 meV per decade. [5,6] However, most of experimental results significantly differ from the aforementioned theoretical predictions. One of dominant factors degrading the overall performance of 2D materials based devices arises from unwanted chemical interactions between deposited metal electrodes and 2D TMDC channel. These chemical interactions originate from incomplete/imperfect covalent/surface bonds of TMDCs and unwanted damages from the direct deposition of metal layers and precursors, which are used during the device fabrication processes. These lead to the creation of unfavorable interface states and pinning of fermi energy levels, which Contact engineering for monolayered transition metal dichalcogenides (TMDCs) is considered to be of fundamental challenge for realizing highperformance TMDCs-based (opto) electronic devices. Here, an innovative concept is established for a device configuration with metallic copper monosulfide (CuS) electrodes that induces sulfur vacancy healing in the monolayer molybdenum disulfide (MoS 2 ) channel. Excess sulfur adatoms from the metallic CuS electrodes are donated to heal sulfur vacancy defects in MoS 2 that surprisingly improve the overall performance of its devices. The electrode-induced self-healing mechanism is demonstrated and analyzed systematically using various spectroscopic analyses, density functional theory (DFT) calculations, and electrical measurements. Without any passivation layers, the self-healed MoS 2 (photo)transistor with the CuS contact electrodes show outstanding room temperature field effect mobility of 97.6 cm 2 (Vs) −1 , On/Off ratio > 10 8 , low subthreshold swing of 120 mV per decade, high photoresponsivity of 1 × 10 4 A W −1 , and detectivity of 10 13 jones, which are the best among back-gated transistors that employ 1L MoS 2 . Using ultrathin and flexible 2D CuS and MoS 2 , mechanically flexible photosensor is also demonstrated, which shows excellent durability under mechanical strain. These findings demonstrate a promising strategy in TMDCs or other 2D material for the development of high performance and functional devices including self-healable sulfide electrodes.
We report on the fabrication and optoelectronic properties of p‐n heterojunction arrays of p+‐type Si and aligned n‐type SnO2 nanowires with high rectification ratios of >104 at ±15 V. The electrical stability of the p‐n heterojunction devices was improved by coating the junction with poly(methylmethacrylate) to minimize the degradation of the interface layer at the junction. As a photodiode an enhanced UV photosensitivity higher than 102 was recorded under reverse bias. Using a large forward bias in the light‐emitting diode mode white light was emitted from the large‐scale heterojunction devices with at least three broad peaks in the visible range, which can be attributed to the interband transitions of the injected electrons or holes mediated by an interfacial SiO2 layer with a contribution of trap‐level energies. These results indicate the high potential of Si/SnO2 nanowires heterojunctions as optoelectronic devices with proper tuning of the recombination center at the junctions.
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