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Shu Min Tan, Martin Pumera
Two-dimensional (2D) materials, such as graphene and transition-metal chalcogenides, were shown in many works as very potent catalysts for industrially important electrochemical reactions, such as oxygen reduction, hydrogen and oxygen evolution, and carbon dioxide reduction. We critically discuss here the development in the field, showing that not only dopants but also impurities can have dramatic effects on catalysis. Note here that the difference between dopant and impurity is merely semantic-dopant is an impurity deliberately added to the material...
February 18, 2019: ACS Nano
A Alka, Vijayendra S Shetti, Mangalampalli Ravikanth
Core-modified porphyrinoids or heteroporphyrinoids are a class of porphyrinoids in which one or more core pyrrole nitrogen atom(s) of the macrocycles are replaced predominantly by group-16 atoms such as O, S, Se, and Te. Telluraporphyrinoids are distinct and interesting from the rest of the chalcogenide atom(s) containing porphyrinoids owing to the larger size of Te and the consequent properties arising from it. The telluraporphyrinoid chemistry is only sporadically investigated and the developments are rather slow compared to the other lighter group-16 atom containing porphyrinoids...
February 18, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
Seunguk Song, Se-Yang Kim, Jinsung Kwak, Yongsu Jo, Jung Hwa Kim, Jong Hwa Lee, Jae-Ung Lee, Jong Uk Kim, Hyung Duk Yun, Yeoseon Sim, Jaewon Wang, Do Hee Lee, Shi-Hyun Seok, Tae-Il Kim, Hyeonsik Cheong, Zonghoon Lee, Soon-Yong Kwon
As the elements of integrated circuits are downsized to the nanoscale, the current Cu-based interconnects are facing limitations due to increased resistivity and decreased current-carrying capacity because of scaling. Here, the bottom-up synthesis of single-crystalline WTe2 nanobelts and low- and high-field electrical characterization of nanoscale interconnect test structures in various ambient conditions are reported. Unlike exfoliated flakes obtained by the top-down approach, the bottom-up growth mode of WTe2 nanobelts allows systemic characterization of the electrical properties of WTe2 single crystals as a function of channel dimensions...
February 6, 2019: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Davide Piccinotti, Behrad Gholipour, Jin Yao, Kevin F MacDonald, Brian E Hayden, Nikolay I Zheludev
A variety of alternative plasmonic and dielectric material platforms-among them nitrides, semiconductors, and conductive oxides-have come to prominence in recent years as means to address the shortcomings of noble metals (including Joule losses, cost, and passive character) in certain nanophotonic and optical-frequency metamaterial applications. Here, it is shown that chalcogenide semiconductor alloys offer a uniquely broad pallet of optical properties, complementary to those of existing material platforms, which can be controlled by stoichiometric design...
February 17, 2019: Advanced Materials
Padmanathan Karthick Kannan, Prabakaran Shankar, Chris Blackman, Chan-Hwa Chung
Surface-enhanced Raman spectroscopy is a powerful and sensitive analytical tool that has found application in chemical and biomolecule analysis and environmental monitoring. Since its discovery in the early 1970s, a variety of materials ranging from noble metals to nanostructured materials have been employed as surface enhanced Raman scattering (SERS) substrates. In recent years, 2D inorganic materials have found wide use in the development of SERS-based chemical sensors owing to their unique thickness dependent physico-chemical properties with enhanced chemical-based charge-transfer processes...
February 18, 2019: Advanced Materials
Oana Cojocaru-Miredin, Henning Hollermann, Antonio M Mio, Anthony Wang, Matthias Wuttig
Interfacial phase change memory devices based on a distinct nanoscale structure called superlattice have been shown to outperform conventional phase-change devices. This improvement has been attributed to the hetero-interfaces, which play an important role for the superior device characteristics. However, the impact of grain boundaries, usually present in large amounts in a standard sputter-deposited superlattice film, on the device performance has not yet been investigated.
 Therefore, in the present work, we investigate the structure and composition of superlattice films by high resolution X-ray diffraction cross-linked with state-of-the art methods, such as correlative microscopy, i...
February 15, 2019: Journal of Physics. Condensed Matter: An Institute of Physics Journal
S Licciardello, J Buhot, J Lu, J Ayres, S Kasahara, Y Matsuda, T Shibauchi, N E Hussey
Correlated electron systems are highly susceptible to various forms of electronic order. By tuning the transition temperature towards absolute zero, striking deviations from conventional metallic (Fermi-liquid) behaviour can be realized. Evidence for electronic nematicity, a correlated electronic state with broken rotational symmetry, has been reported in a host of metallic systems1-5 that exhibit this so-called quantum critical behaviour. In all cases, however, the nematicity is found to be intertwined with other forms of order, such as antiferromagnetism5-7 or charge-density-wave order8 , that might themselves be responsible for the observed behaviour...
February 13, 2019: Nature
Charlie Gréboval, Eva Izquierdo, Clément Livache, Bertille Martinez, Marion Dufour, Nicolas Goubet, Nicolas Moghaddam, Junling Qu, Audrey Chu, Julien Ramade, Hervé Aubin, Hervé Cruguel, Mathieu Silly, Emmanuel Lhuillier, Sandrine Ithurria
We demonstrate the growth of 2D nanoplatelets (NPLs) made of a HgTe/CdS heterostructure, with an optical absorption reaching the shortwave infrared range. The material is an interesting platform to investigate the effect of dimensionality (0D vs. 2D) and confinement on the electronic spectrum and carrier dynamics in colloidal materials. We bring consistent evidence for the p-type nature of this material from transport and photoemission measurements. The majority carrier dynamics probed using pump-probe photoemission is found to be mostly dependent on the presence of a confinement barrier at the surface rather than on the material dimensionality...
February 13, 2019: Nanoscale
Huanglong Li, John Robertson
The electronic structure and conduction mechanism of chalcogenide-based Ovonic threshold switches (OTS) used as selectors in cross-point memory arrays is derived from density functional calculations and quasi-Fermi level models. The switching mechanism in OTS is primarily electronic. This uses a specific electronic structure, with a wide tail of localized states below the conduction band edge. In amorphous GeSe2-x the conduction band consists of Ge-Se σ*states with a low effective mass, and with a broad tail of localized Ge-Ge σ* states below this band edge...
February 12, 2019: Scientific Reports
Hazel A Fargher, Nathanael Lau, Lev N Zakharov, Michael M Haley, Darren W Johnson, Michael D Pluth
Synthetic supramolecular receptors have been widely used to study reversible solution binding of anions; however, few systems target highly-reactive species. In particular, the hydrochalcogenide anions hydrosulfide (HS- ) and hydroselenide (HSe- ) have been largely overlooked despite their critical roles in biological systems. Herein we present the first example of reversible HSe- binding in two distinct synthetic supramolecular receptors, using hydrogen bonds from N-H and aromatic C-H moieties. The arylethynyl bisurea scaffold 1 t Bu achieved a binding affinity of 460 ± 50 M-1 for HSe- in 10% DMSO- d 6 /CD3 CN, whereas the tripodal-based receptor 2CF3 achieved a binding affinity of 290 ± 50 M-1 in CD3 CN...
January 7, 2019: Chemical Science
Tian Gu, Juejun Hu
No abstract text is available yet for this article.
February 11, 2019: Nature Nanotechnology
Deepak S Patil, Manisha Konale, Tomas Wagner
Impedance spectroscopy is a valuable tool for the analysis of the ionic conductivity of both solid and liquid state materials. Chalcogenide glasses are well known for their high ionic conductivity nature and wide compositional flexibility. As the GeSbSe material has high glass forming ability, it is expected that the materials can be doped with a high amount of foreign element (in the present case Ag). For all of these reasons, the GeSbSe materials can be expected as a potential candidate for solid state electrolyte for ionic batteries...
February 2019: Data in Brief
Kai Jiao, Jinmei Yao, Zheming Zhao, Xiange Wang, Nian Si, Xunsi Wang, Peng Chen, Zugang Xue, Youmei Tian, Bin Zhang, Peiqing Zhang, Shixun Dai, Qiuhua Nie, Rongping Wang
We have prepared a well-structured tellurium chalcogenide (ChG) fiber with a specialized double cladding structure by an improved extrusion method, and experimentally demonstrated an ultra-flat mid-infrared (MIR) supercontinuum (SC) generation in such a fiber. The step-index fiber had an optical loss of <1 dB/m in a range from 7.4 to 9.7 μm with a minimum loss of 0.69 dB/m at 7.87 μm. Simulation showed that an all-normal dispersion profile can be realized in this double cladding tellurium fiber. An ultra-flat MIR SC spectrum (~3...
February 4, 2019: Optics Express
Sourabh Kumar, Chiranjit Mondal, Biswarup Pathak
Smythite (Fe3S4) is an iron-based chalcogenide, having a lamellar structure compared to compositionally same another iron-based chalcogenide mineral greigite (Fe3S4). Because of the abundance of such transition metal based chalcogenides, they offer the low-cost productivity of spintronic-based devices. Here, we have studied the charge transfer processes and complex magnetic ordering in a two dimensional (2D) smythite lattice. We find that Fe2+/Fe3+ redox couple and complex magnetic ordering govern these charge transfer processes...
February 6, 2019: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Behrad Gholipour, Davide Piccinotti, Artemios Karvounis, Kevin F MacDonald, Nikolay I Zheludev
Photonic materials with tuneable and switchable ultraviolet (UV) to high-energy-visible (HEV) optical properties would benefit applications in sensing, high-density optical memory, beam-steering, adaptive optics and light modulation. Here, for the first time, we demonstrate a non-volatile switchable dielectric metamaterial operating in the UV-HEV spectral range. Nano-grating metamaterials in a layered composite of low-loss ZnS/SiO2 and the chalcogenide phase-change medium germanium antimony telluride (Ge2Sb2Te5) exhibit reflection resonances at UV-HEV wavelengths that are substantially modified by light-induced (amorphous-crystalline) phase transitions in the chalcogenide layer...
February 5, 2019: Nano Letters
Maxwell A T Marple, Vuthtyra Yong, Sabyasachi Sen
The composition dependence of the fragility of Six Se1-x liquids with 0.05 ≤ x ≤ 0.33 is determined using the calorimetric method and is found to be rather similar to that characteristic of their Ge analogues. In addition, the nature and the time scale of the structural relaxation of the Si25 Se75 glass during aging at 40 K below Tg are measured using Raman spectroscopy. The structural relaxation in this glass, which belongs to the so-called intermediate phase, involves progressive conversion of the doubly edge-shared SiSe4/2 tetrahedra E2 into singly edge-shared E1 and corner-shared E0 tetrahedra upon lowering of temperature...
January 28, 2019: Journal of Chemical Physics
Xiaoli Sun, Jingliang He, Bingnan Shi, Baitao Zhang, Kejian Yang, Chengqian Zhang, Ruihua Wang
We successfully fabricated the high-quality few-layered α-In2 Se3 and investigated its carrier dynamics and nonlinear optical absorption properties by pump-probe and open-aperture Z-scan technologies. Intra- and inter-band relaxation times were determined to be 7.2 ps and 270 ps, respectively, and the effective nonlinear absorption coefficient was measured as βeff =-3.9×103   cm/GW (1064 nm). Based on α-In2 Se3 saturable absorber, a continuous-wave mode-locking operation was realized. Pulse duration, repetition rate, and maximum output power were measured to be 352 fs, 42...
February 1, 2019: Optics Letters
Jianian Cheng, Binghua Lei, Chen Zhou, Shilie Pan, Zhihua Yang
The introduction of d10-metal cations is of importance in the design of infrared nonlinear optical materials. The role of d10-metal cations on the band gap and the second-harmonic generation (SHG) effect as well as the structure-property relationship were investigated in the Li2MGeS4 (M = Cd, Hg) and AB2S4 (A = Cd, Hg; B = Al, Ga) systems by using the first-principles calculations. The results show that the decreased band gap is related to a higher valence band maximum (VBM) caused by the larger dp repulsion from the Hg-5d orbitals and a downshift in the conduction band minimum (CBM) due to the lower energy of the Hg-6s orbitals...
January 29, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
Prakash Pitchappa, Abhishek Kumar, Saurav Prakash, Hariom Jani, Thirumalai Venkatesan, Ranjan Singh
The strikingly contrasting optical properties of various phases of chalcogenide phase change materials (PCM) has recently led to the development of novel photonic devices such as all-optical non-von Neumann memory, nanopixel displays, color rendering, and reconfigurable nanoplasmonics. However, the exploration of chalcogenide photonics is currently limited to optical and infrared frequencies. Here, a phase change material integrated terahertz metamaterial for multilevel nonvolatile resonance switching with spatial and temporal selectivity is demonstrated...
January 27, 2019: Advanced Materials
Matthew J Hamer, Johanna Zultak, Anastasia V Tyurnina, Viktor Zólyomi, Daniel Terry, Alexei Barinov, Alistair Garner, Jack Donoghue, Aidan P Rooney, Viktor Kandyba, Alessio Giampietri, Abigail Graham, Natalie Teutsch, Xue Xia, Maciej Koperski, Sarah J Haigh, Vladimir I Fal'ko, Roman Vladislavovich Gorbachev, Neil Richard Wilson
Atomically thin films of III-VI post-transition metal chalcogenides (InSe and GaSe) form an interesting class of two-dimensional semiconductor that feature a strong variation of their band gap as a function of the number of layers in the crystal and, specifically for InSe, an expected crossover from a direct gap in the bulk to a weakly indirect band gap in monolayers and bilayers. Here, we apply angle resolved photoemission spectroscopy with submicrometer spatial resolution (μARPES) to visualise the layer-dependent valence band structure of mechanically exfoliated crystals of InSe...
January 24, 2019: ACS Nano
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