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InGaN quantum wells (QWs) grown on c-plane sapphire substrate experience strain due to the lattice mismatch. The strain generates a strong piezoelectric field in QWs that contributes to THz emission under ultrafast excitation. Physical parameters such as QW width, period number, and Indium concentration can affect the strength of the piezoelectric field and result in THz emission. Experimental parameters such as pump fluence, laser energy, excitation power, pump polarization angle, and incident angle can be tuned to further optimize the THz emission. This review summarizes the effects of physical and experimental parameters of THz emission on InGaN QWs. Comparison and relationship between photoluminescence properties and THz emission in QWs are given, which further explains the origin of THz emission in InGaN QWs. [ABSTRACT FROM AUTHOR]

Ferromagnetism is explored in Cr3C2 from microscopic to electronic levels and the spin coupling is attributed to the p electrons of the nearest‐neighbor carbon atoms around the Cr–C atomic interactions. By using the spin‐polarized density functional calculations, four models are formulated. The models reveal that the C atoms seated in tri‐prism I site can induce magnetic moments and the C vacancies can also take part in the induced magnetic moment. The p–d orbital interactions between C interstitial atom and Cr atom contribute to two asymmetric states of majority and minority spins and lead to weak magnetic moments. The C interstitial atoms and C vacancies in the crystal lattice of Cr3C2 are observed by high‐resolution transmission electron microscopy and electron‐spin resonance (ESR) techniques. The magnetic properties of Cr3C2 are investigated by a superconducting quantum interference device. [ABSTRACT FROM AUTHOR]

Broad and low‐intensity Raman peaks are usually expected from nanocrystalline thin semiconductor films. The inherently weak Raman scattering phenomenon can be further deteriorated by unwanted background signals preventing the successful Raman analysis of an analyte. In this study, the resonant and surface‐enhanced Raman scattering techniques were combined to detect CuO and Cu2O phases in the partially oxidized nanocrystalline copper film that were otherwise undetectable. Heat treatment resulted in increased oxidation and phase transition from multiphase to single CuO phase that was in situ observed by temperature‐dependent Raman measurements. Detailed understanding of the film properties and substrate interaction was made by using several characterization techniques. [ABSTRACT FROM AUTHOR]

Flexible sensors with excellent sensitivity and stable performance are attracting more and more attention in emerging electronics. Herein, silver microflakes (AgMFs) as conductive filler in polyaniline (PANI)/polyurethane (PU) matrix are used to prepare the AgMFs/PANI/PU strain sensor by simple mixing and curing process. The AgMFs/PANI/PU strain sensor has high sensitivity (GF=173.66), ultra‐short response time (10 ms), and reassuring cycle stability (>4000 times). Excellent sensor performance demonstrates its unlimited potential for health monitoring, such as joint motion, breathing and pulse beat. [ABSTRACT FROM AUTHOR]

Resonant Raman scattering is highly desired for material study. It is experimentally not easy to reach the resonant scattering interaction between an incident photon and a material due to the limited available laser wavelengths. In this study, by employing silver plasmonic nanoparticles deposited on glass substrate and by in situ adjusting the cadmium sulfide (CdS) band gap through heat treatment, resonant Raman scattering condition (laser wavelength of 514.5 nm) was fully achieved in nanocrystalline CdS thin films. The dramatically enhanced Raman scattering allowed us to in situ monitor the phase transition that occurred during the heat treatment and to quantitatively characterize the fraction of the zincblende (cubic) CdS in the main base of wurtzite (hexagonal) CdS. Raman multi-phonon and the corresponding high-order scattering modes were observed due to the much enhanced surface nanoplasmonic electric field. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A series of alluaudite Na2Fe3− xMn x(PO4)3 microcompounds, which self-assembled from primary nanorods, were prepared successfully through a solvothermal method. As a promising candidate cathode for sodium-ion batteries, it is necessary to obtain a deeper understanding of the relationship between the structure and physicochemical properties of these materials. The local electronic and geometric environments were systematically investigated, for the first time, by using a combination of soft/hard X-ray absorption, IR, and Mössbauer spectroscopy. The results show that the electrochemical performance is not only associated with morphology, but also with the electronic and crystalline structure. With the introduction of manganese into the lattice, the long-range order maintains the isostructural framework and the lattice parameters expand as expected. However, for short-range order, PO4 tetrahedra and MO6 octahedra (M=Fe and Mn) become more severely distorted as a function of Mn concentration. Meanwhile, larger MnO6 octahedra will compress the space of FeO6 octahedra, which will result in stronger core/electron-electron interactions for Fe, as characterized by hard/soft X-ray absorption spectra. These slight changes in the electronic and local structures lead to different electrochemical performances with changes to the manganese content. Moreover, other physicochemical properties, such as magnetic behavior, are also confirmed to be correlated with these different electron interactions and local geometric environments. [ABSTRACT FROM AUTHOR]