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Matin Amani, Chaoliang Tan, George Zhang, Chunsong Zhao, James Bullock, Xiaohui Song, Hyungjin Kim, Vivek Raj Shrestha, Yang Gao, Kenneth B Crozier, Mary Scott, Ali Javey
Two-dimensional (2D) materials, particularly black phosphorous (bP), have demonstrated themselves to be excellent candidates for high-performance infrared photodetectors and transistors. However, high-quality bP can be only obtained via mechanical exfoliation from high temperature- and high-pressure-grown bulk crystals and degrades rapidly when exposed to ambient conditions. Here, we report solution-synthesized and air-stable quasi-2D tellurium (Te) nanoflakes for short-wave infrared (SWIR) photodetectors. We perform comprehensive optical characterization via polarization-resolved transmission and reflection measurements, and report the absorbance and complex refractive index of Te crystals...
June 18, 2018: ACS Nano
Xiaoyan Yang, Yi Li, Peng Zhang, Rongmei Zhou, Hailong Peng, Dan Liu, Jianzhou Gui
Based on the photochemical property of semiconductors, a light irradiation-assisted strategy has been designed to synthesize the rod-type PtO2/ZnO catalyst with well-defined structure, using one-dimensional ZnO nanorods as carriers. The high crystallinity and uniform crystal structure of ZnO matrix conduct the in-situ deposition of PtO2 nanoparticles with 1.5-3 nm, which are evenly and densely anchored on the surface. Those small-sized and well dispersed PtO2 nanoparticles endow the PtO2/ZnO catalyst a superior catalytic performance for reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), which can convert all substrates within 8 min...
June 18, 2018: ACS Applied Materials & Interfaces
Guilan Xu, Jianchen Shen, Shumei Chen, Yujie Gao, Huabin Zhang, Jian Zhang
Graphitic carbon nitride (g-C3N4) is an actively investigated metal-free photocatalyst for solar energy conversion. However, primary g-C3N4 usually exhibits limited utilization of visible light and fast combination of photoexcited charge carriers, resulting in low photocatalytic H2 evolution activity. Defect-modified g-C3N4 shows much enhanced photocatalytic H2 evolution activity owing to extended light absorption as well as efficient charge separation and transfer. Here, the photocatalyst simultaneously containing nitrogen vacancies and O-doping is successfully developed by using a two-step post-synthetic strategy for photocatalytic H2 evolution, resulting in a greatly-boosted H2 evolution activity (1...
June 18, 2018: Physical Chemistry Chemical Physics: PCCP
Sergio Bietti, Francesco Basso Basset, David Scarpellini, Alexey Fedorov, Andrea Ballabio, Luca Esposito, Martin Elborg, Takashi Kuroda, Akos Nemcsics, Lajos Toth, Cristian Manzoni, Caterina Vozzi, Stefano Sanguinetti
A hybrid metal-semiconductor nanosystem for the generation of THz radiation, based on the fabrication of GaAs quantum molecules-Ga metal nanoparticles complexes through a self assembly approach, is proposed. The role of the growth parameters, the substrate temperature, the Ga and As flux during the quantum dot molecule fabrication and the metal nanoparticle alignment is discussed. The tuning of the relative positioning of quantum dot molecules and metal nanoparticles is obtained through the careful control of Ga droplet nucleation sites via Ga surface diffusion...
June 18, 2018: Nanotechnology
Xugang Guo, Jianhua Chen, Kun Yang, Xin Zhou
The fusion of heteroaromatic rings into ladder-type heteroarenes can stabilize frontier molecular orbitals and lead to improved physicochemical properties, which are beneficial for applications in various optoelectronic devices. Hence, ladder-type heteroarenes, which feature highly planar backbones and well delocalized π-conjugation, recently have emerged as a type of promising organic semiconductors with excellent device performance in organic photovoltaics and organic field-effect transistors. In this Focus Review, we summarize the recent advances in ladder-type heteroarenes based organic semiconductors including hole-transporting and electron-transporting molecular semiconductors as well as fully ladder-type conjugated polymers towards their applications in organic photovoltaics and field-effect transistor...
June 17, 2018: Chemistry, An Asian Journal
Daniel Wurmbrand, Jörg Wolfram Anselm Fischer, Rose Rosenberg, Klaus Boldt
A fibrillar, polymeric intermediate (Cd2Se)n was isolated from the synthesis of CdSe nanorods, which suggests that the reactants themselves can template anisotropic growth. It is shown that high monomer concentration is the principal factor favouring this reaction pathway. The intermediate is distinct from crystalline semiconductor or small clusters and is surprisingly temperature-stable below 250 °C.
June 18, 2018: Chemical Communications: Chem Comm
Teck Lip Dexter Tam, Chee Koon Ng, Xuefeng Lu, Zheng Long Lim, Jishan Wu
A highly π-acidic dipyridinium-naphthalene diimide acceptor shows anion-π interactions with halides and PF6-. Lewis basicity and redox potential of the anion affect the chemistry, and photophysical and electrochemical properties, as well as both ionic and electrical conductivities. Our results provide insights into doping, degradation and ion transport mechanisms in organic n-type semiconductors.
June 18, 2018: Chemical Communications: Chem Comm
Jacobine J H A van Hest, Gerhard A Blab, Hans C Gerritsen, Celso de Mello Donega, Andries Meijerink
The localized inner 4f shell transitions of lanthanide ions are largely independent of the local surroundings. The luminescence properties of Ln3+ ions doped into nanocrystals (NCs) are therefore similar to those in bulk crystals. Quantum size effects, responsible for the unique size-dependent luminescence of semiconductor NCs, are generally assumed not to influence the optical properties of Ln3+ -doped insulator NCs. However, phonon confinement effects have been reported to hamper relaxation between closely spaced Stark levels in Ln3+ -doped NCs...
February 22, 2018: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Vojtěch Svatoš, Imrich Gablech, B Robert Ilic, Jan Pekárek, Pavel Neužil
Carbon nanotubes (CNTs) have near unity infrared (IR) absorption efficiency, making them extremely attractive in IR imaging devices. Since CNT growth occurs at elevated temperatures, integration of CNTs with IR imaging devices is challenging and has not yet been achieved. Here we show a strategy for implementing CNTs as IR absorbers using differential heating of thermally-isolated microbolometer membranes in a C2 H2 environment. During the process, CNTs were catalytically grown on the surface of a locally-heated membrane while the substrate was maintained at an ambient temperature...
March 2018: Journal of Applied Physics
Douglas O'Reagan, Lee Fleming
The "FinFET" design for transistors, developed at the University of California, Berkeley, in the 1990s, represented a major leap forward in the semiconductor industry. Understanding its origins and importance requires deep knowledge of local factors, such as the relationships among the lab's principal investigators, students, staff, and the institution. It also requires understanding this lab within the broader network of relationships that comprise the semiconductor industry-a much more difficult task using traditional historical methods, due to the paucity of sources on industrial research...
2018: Technology and Culture
Rui Peng, Yandong Ma, Shuai Zhang, Baibiao Huang, Ying Dai
Two-dimensional valleytronic systems can provide information storage and processing advantages that complement or surpass those of conventional charge- and spin-based semiconductor technologies. The major challenge currently is to realize valley polarization for manipulating the valley degree of freedom. Here, we propose that valley polarization can be readily achieved in Janus single-layer MoSSe through magnetic doping, which is highly feasible in experiment. Due to inversion symmetry breaking combined with strong spin-orbit coupling (SOC), the pure single-layer MoSSe harbors an intriguing multivalleyed band structure and strong coupled spin and valley physics...
June 19, 2018: Journal of Physical Chemistry Letters
Audrey Hammack, Rashed T Rihani, Bryan J Black, Joseph J Pancrazio, Bruce E Gnade
Substrate-integrated microelectrode arrays (MEAs) are non-invasive platforms for recording supra-threshold signals, i.e. action potentials or spikes, from a variety of cultured electrically active cells, and are useful for pharmacological and toxicological studies. However, the MEA substrate, which is often fabricated using semiconductor processing technology, presents some challenges to the user. Specifically, the electrode encapsulation, which may consist of a variety of inorganic and organic materials, requires a specific substrate preparation protocol to optimize cell adhesion to the surface...
June 16, 2018: Biomedical Microdevices
Stefan Doering, Andre Wachowiak, Hagen Roetz, Stefan Eckl, Thomas Mikolajick
Scanning spreading resistance microscopy (SSRM) with its high spatial resolution and high dynamic signal range is a powerful tool for two-dimensional characterization of semiconductor dopant areas. However, the application of the method is limited to devices in equilibrium condition, as the investigation of actively operated devices would imply potential differences within the device, whereas SSRM relies on a constant voltage difference between sample surface and probe tip. Furthermore, the standard preparation includes short circuiting of all device components, limiting applications to devices in equilibrium condition...
June 1, 2018: Ultramicroscopy
P N Timonin
High-density (HD) percolation describes the percolation of specific κ-clusters, which are the compact sets of sites each connected to κ nearest filled sites at least. It takes place in the classical patterns of independently distributed sites or bonds in which the ordinary percolation transition also exists. Hence, the study of series of κ-type HD percolations amounts to the description of classical clusters' structure for which κ-clusters constitute κ-cores nested one into another. Such data are needed for description of a number of physical, biological, and information properties of complex systems on random lattices, graphs, and networks...
May 2018: Physical Review. E
Matthew Z Bellus, Masoud Mahjouri-Samani, Samuel D Lane, Akinola D Oyedele, Xufan Li, Alexander A Puretzky, David Geohegan, Kai Xiao, Hui Zhao
In-plane heterojuctions formed from two monolayer semiconductors represent the finest control of electrons in condensed matter, and has attracted significant interests. Various device studies have shown the effectiveness of such structures to control electronic processes, illustrating their potentials for electronic and optoelectronic applications. However, information about the physical mechanisms of charge carrier transfer across the junctions is still rare, mainly due to the lack of adequate experimental techniques...
June 15, 2018: ACS Nano
Li Wang, Cheng Wang, Jie Wang, Fang Bo, Mian Zhang, Qihuang Gong, Marko Lončar, Yun-Feng Xiao
Lithium niobate (LN) is the workhorse for modern optoelectronics industry and nonlinear optics. High quality (Q) factor LN microresonators are promising candidates for applications in optical communications, quantum photonics, and sensing. However, the phase-matching requirement of traditional evanescent coupling methods poses significant challenges to achieve high coupling efficiencies of the pump and signal light simultaneously, ultimately limiting the practical usefulness of these high Q factor LN resonators...
June 15, 2018: Optics Letters
Yuemei Li, Rui Wang, Yanling Xu, Wei Zheng, Yongmei Li
Photodynamic therapy (PDT) is a noninvasive therapeutic technique. Upconversion nanoparticles (UCNPs) hold promise for photodynamic therapy (PDT). UCNPs with antistokes emission can improve the tissue penetration depth of PDT. However, the low upconversion efficiency poses a strong limit on further development of PDT. The core/shell structure Yb/Tm/GZO@SiO2 UCNPs are designed, which can form multistep cascade energy transfer from sillica shell to core Ga-doped Yb/Tm/ZnO. Compared with Yb/Tm/ZnO upconversion (UC) semiconductor nanoparticles (SNCs), the multistep cascade energy transfer process provides about seven times enhanced UCL emission...
June 15, 2018: Inorganic Chemistry
Sanchari Shome, Surya Prakhash Singh
The first methodology of ruthenium carboxylate-catalysed single step oxidative cross coupling that challenges the conventional Stille and Suzuki coupling reactions, affording BT and MFBT derivatives in the absence of protecting groups, was developed. Both mono and bi-arylated derivatives are formed in moderate to high yields (30-75%). Innately high selectivity, low catalyst loading and lack of formation of regio-isomers ensure the large-scale synthesis of various photonic and electronic materials employing this method...
June 15, 2018: Chemical Communications: Chem Comm
Yanbing Wu, Zongyu Huang, Huating Liu, Chaoyu He, Lin Xue, Xiang Qi, Jianxin Zhong
We have studied the stable geometries, band structures and magnetic properties of transition-metal (V, Cr, Mn, Fe, Co and Ni) atoms absorbed on MoS2/h-BN heterostructure systems by first-principles calculations. By comparing the adsorption energies, we find that the adsorbed transition metal (TM) atoms prefer to stay on the top of Mo atoms. The results of the band structure without spin-orbit coupling (SOC) interaction indicate that the Cr-absorbed systems behave in a similar manner to metals, and the Co-absorbed system exhibits a half-metallic state...
June 15, 2018: Physical Chemistry Chemical Physics: PCCP
A Kandemir, H Sahin
Motivated by the recent successful synthesis of Janus type single layers of transition metal dichalcogenides, we investigate the stability, vibrational and electronic properties of the Janus single layer structure of WSSe and its bilayers by means of density functional theory. The structural and vibrational analysis show that the Janus single layer of WSSe forms a dynamically stable structure in the 2H phase. Owing to its non-centrosymmetric structure, the Janus WSSe single layer has two in-plane (E) and two out-of-plane (A) Raman active phonon modes...
June 15, 2018: Physical Chemistry Chemical Physics: PCCP
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