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We theoretically study the strain effect on the Casimir interactions in graphene based systems. We found that the interactions between two strained graphene sheets are strongly dependent on the direction of stretching. The influence of the strain on the dispersion interactions is still strong in the presence of dielectric substrates but is relatively weak when the substrate is metallic. Our studies would suggest new ways to design next generation devices.
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Sergei V. Zhukovsky Igor E. Protsenko Renat Sh. Ikhsanov Igor V. Smetanin Viktoriia E. Babicheva Alexander V. Uskov 《固体物理学:研究快报》2015,9(10):570-574
Transition absorption of a photon by an electron passing through a boundary between two media with different permittivities is described both classically and quantum mechanically. Transition absorption is shown to make a substantial contribution to photoelectron emission at a metal/semicon‐ductor interface in nanoplasmonic systems, and is put forth as a possible microscopic mechanism of the surface photoelectric effect in photodetectors and solar cells containing plasmonic nanoparticles.
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An observation of negative refraction in the naturally obtained composition of graphene and barium ferrite is reported. The capacitance and inductance measurements revealed the electric and magnetic resonances accompanied with the negative values of permittivity and permeability in the overlapped frequency range. According to the “left‐handed” media approach such a material is characterized by negative refraction. The derived values of the real part of refractive index are negative at the frequencies above 500 MHz.
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High‐temperature ferroelectricity and strong magnetoelectric effects in a hybrid organic–inorganic perovskite framework 下载免费PDF全文
Ying Tian Alessandro Stroppa Yi‐Sheng Chai Paolo Barone Manuel Perez‐Mato Silvia Picozzi Young Sun 《固体物理学:研究快报》2015,9(1):62-67
A Cu‐based organic–inorganic perovskite framework exhibits high‐temperature ferroelectricity with strong magnetoelectric effects. Both electric field control of magnetization and magnetic field control of polarization are realized. Theoretical calculations suggest that a new mechanism of hybrid improper ferroelectricity arising from the Jahn–Teller distortions of magnetic metal ions and tilting of the organic cations are responsible for the peculiar multiferroic behaviors.
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Jianyu Wang Huabin Sun Yun Sheng Fan Gao Yao Yin Yun Li Lijia Pan Youdou Zheng Yi Shi Takashi Sekiguchi 《固体物理学:研究快报》2015,9(8):466-469
Surface‐diffusion‐induced spontaneous Ga incorporation process is demonstrated in ZnO nanowires grown on GaN substrate. Crucially, contrasting distributions of Ga atoms in axial and radial directions are experimentally observed. Ga atoms uniformly distribute along the ~10 μm long ZnO nanowire and show a rapidly gradient distribution in the radial direction, which is attributed substantially to the difference between surface and volume diffusion. The understanding on the incorporation process can potentially modulate doping and properties in semiconductor nanomaterials.
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Jonathan Joel Bart Vermang Jes Larsen Olivier Donzel‐Gargand Marika Edoff 《固体物理学:研究快报》2015,9(5):288-292
An optimized test structure to study rear surface passivation in Cu(In,Ga)Se2 (CIGS) solar cells by means of photoluminescence (PL) is developed and tested. The structure – illustrated in the abstract figure – is examined from the rear side. To enable such rear PL assessment, a semi‐transparent ultra‐thin Mo layer has been developed and integrated in place of the normal rear contact. The main advantages of this approach are (i) a simplified representation of a rear surface passivated CIGS solar cell is possible, (ii) it is possible to assess PL responses originating close to the probed rear surface, and (iii) a stable PL response as a function of air exposure time is obtained. In this work, PL measurements of such structures with and without rear surface passivation layers have been compared, and the measured improvement in PL intensity for the passivated structures is associated with enhanced CIGS rear interface properties.
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Numerical modeling of photovoltaic efficiency of n‐type GaN nanowires on p‐type Si heterojunction 下载免费PDF全文
In this Letter, we investigate the photovoltaic properties of heterojunction solar cells based on n‐GaN nanowire (NW)/ p‐Si substrate heterostructures by means of numerical modeling. Antireflection properties of the NW array on the top of Si substrate were studied theoretically to show an order of magnitude enhancement in antireflection properties in comparison to the pure Si surface (2.5% vs. 33.8%). In order to determine the optimal morphology and doping levels of the structure with maximum possible efficiency we simulated its properties. The carried out simulation showed that the maximum efficiency should be more than 20% under AM1.5D illumination. The proposed design opens new perspectives and opportunities in the field of heterojunction tandem solar cell researches.
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We present a detailed temperature‐dependent (4–300 K) spectroscopic study of DyMnO3 single crystals with distorted perovskite structure. Energies of 36 crystal‐field levels of Dy3+ in paramagnetic DyMnO3 were determined. The Dy3+ ground Kramers doublet does not split at and splits below Tlock = 18 K. The splitting grows fast at temperatures near and reaches Δ0 ≈ 11 ± 2 cm–1 at 4 K. Using the experimental temperature dependence Δ0(T), we calculate the dysprosium magnetic moment mDy(T) and the dysprosium contribution into specific heat and magnetic susceptibility. Analysing all the experimental data, we conclude that the Dy–Mn interaction is of the Dzyaloshinskii–Moriya type.
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Impact of strain induced by polymer curing in benzocyclobutene embedded semiconductor nanostructures
Genziana Bussone Emmanouil Dimakis Raphael Grifone Andreas Biermanns Abbes Tahraoui Dina Carbone Lutz Geelhaar Tobias U. Schülli Ullrich Pietsch 《固体物理学:研究快报》2014,8(12):1007-1010
Polymers such as benzocyclobutene are commonly used as embedding materials for semiconductor nanostructures. During the curing process of the polymer up to 250 °C, a significant impact of strain can be induced on the embedded semiconductor material due to different thermal expansion coefficients. This strain has been revealed by X‐ray diffraction in free‐standing GaAs nanowires grown on a silicon substrate, embedded in a polymer matrix. It will be shown that this strain is released during the X‐ray irradiation if additionally an external static electric field is applied.
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Low leakage stoichiometric SrTiO3 dielectric for advanced metal–insulator–metal capacitors 下载免费PDF全文
Mihaela Popovici Ben Kaczer Valeri V. Afanas'ev Gabriele Sereni Luca Larcher Augusto Redolfi Sven Van Elshocht Malgorzata Jurczak 《固体物理学:研究快报》2016,10(5):420-425
Metal–insulator–metal capacitors (MIMCAP) with stoichiometric SrTiO3 dielectric were deposited stacking two strontium titanate (STO) layers, followed by intermixing the grain determining Sr‐rich STO seed layer, with the Ti‐rich STO top layer. The resulted stoichiometric SrTiO3 would have a structure with less defects as demonstrated by internal photoemission experiments. Consequently, the leakage current density is lower compared to Sr‐rich STO which allow further equivalent oxide thickness downscaling.
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The excitons in the orthorhombic phase of the perovskite CH3NH3PbI3 are studied using the effective mass approximation. The electron–hole interaction is screened by a distance‐dependent dielectric function, as described by the Haken potential or the Pollmann–Büttner potential. The energy spectrum and the eigenfunctions are calculated for both cases. The results show that the Pollmann–Büttner model, using the corresponding parameters obtained from ab initio calculations, provides better agreement with the experimental results.
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Exchange bias at low fields exhibited by the interface between epitaxial layers of ferromagnetic and charge‐ordered rare‐earth manganites 下载免费PDF全文
Epitaxial thin films of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and charge‐ordered, antiferromagnetic Y0.5Ca0.5MnO3 (YCMO) were deposited on SrTiO3 (100) substrates by pulsed laser deposition (PLD). The heterostructure undergoes tetragonal distortion due to strong biaxial tensile strain imposed by the substrate. The LSMO–YCMO bilayers exhibit significant exchange bias (EB) across the interface even in a very small remnant magnetic field (~5 Oe) present in the superconductor magnet. The unidirectional exchange anisotropy at the interface can be switched by reversing the polarity of the remnant magnetic field.
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Spectral dependence of light extraction efficiency of high‐power III‐nitride light‐emitting diodes 下载免费PDF全文
Using the recently suggested method of processing the data on external quantum efficiency as a function of output optical power, we have estimated the dependence of light extraction efficiency of high‐power light‐emitting diodes (LEDs) on their emission wavelength varied between 425 nm and 540 nm. The extraction efficiency is found to increase with the wavelength from ~80% to ~85% in this spectral range and to correlate with the wavelength dependence of reflectivity of the large‐area p‐electrode being the essential unit of the LED chip design. The correlation found identifies the incomplete reflection of emitted light from the electrode as the major mechanism eventually controlling the spectral dependence of the efficiency of light extraction from the LEDs.
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Lead‐free mesoscopic Cs2SnI6 perovskite solar cells using different nanostructured ZnO nanorods as electron transport layers 下载免费PDF全文
Xiaofeng Qiu Yanan Jiang Hailiang Zhang Zhiwen Qiu Shuai Yuan Ping Wang Bingqiang Cao 《固体物理学:研究快报》2016,10(8):587-591
Lead‐free and more air‐stable perovskite Cs2SnI6 absorber with a direct bandgap of 1.48 eV is synthesized via a modified solution process. Different nanostructured ZnO nanorod arrays as electron transport layers and hole blocking layers are grown by controlling the seed layer and used to fabricate mesoscopic perovskite solar cells with Cs2SnI6 as light absorber layer. The influences of ZnO seed layers and nanorod morphology on the device photovoltaic performance were also investigated. With careful control of ZnO nanorod length and pore size to ensure high loading of the Cs2SnI6 absorber, we achieved power conversion efficiency of near 1%.
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Jing Wang Ningning Zu Xianfeng Hao Yuanhui Xu Zhiping Li Zhijian Wu Faming Gao 《固体物理学:研究快报》2014,8(9):776-780
Structural, electronic and magnetic properties of Sr2FeOsO6 have been revisited by using the first‐principle calculations. Semiconducting behavior is reproduced. The band gap is 0.09 eV from generalized gradient approximation (GGA) and 0.30 eV by considering both SOC and U, a bit larger than the experimental observed 0.125 eV. In the C‐type antiferromagnetic configuration, spin frustration is found by analysing the magnetic exchange parameters, explaining the experimental observed magnetic complexity.
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Efficient synthesis and tailoring of magnetic and dielectric properties of Pb‐free perovskite‐like ABX3 metal‐organic frameworks 下载免费PDF全文
Nandita Abhyankar Minseong Lee Megan Foley Eun Sang Choi Geoffrey Strouse Harold W. Kroto Naresh S. Dalal 《固体物理学:研究快报》2016,10(8):600-605
Perovskite‐like metal‐organic frameworks (MOFs) are hybrid materials of high interest for their potential in information storage technology, as Pb‐free substitutes for the widely used lead zirconate titanate (PZT) family of multiferroics. We report here a new, microwave‐assisted method of synthesis for perovskite‐like MOFs, which exploits the advantages of rapid and volumetric heating by microwaves in order to achieve synthesis within minutes, compared to days required by previously reported methods. The preliminary results demonstrate a broad control over the size and morphology of the products, by minor changes in the reaction conditions. An investigation of the effects of size and morphology on the magnetic and dielectric properties is presented here.
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Po‐Chun Chen Yu‐Chien Chiu Zhi‐Wei Zheng Chun‐Hu Cheng Yung‐Hsien Wu 《固体物理学:研究快报》2016,10(12):919-923
We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (Ilight/Idark) of 8.2 × 103 at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.
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Direct correlation of microstructure and device performance of liquid phase crystallized Si thin film solar cells on glass 下载免费PDF全文
Sven Kühnapfel Stefan Gall Paul Sonntag Norbert Schäfer Daniel Abou‐Ras 《固体物理学:研究快报》2016,10(9):657-661
Si thin films on glass grown by liquid phase crystallization (LPC) exhibit large grains resembling those in multicrystalline Si wafers. The present work gives direct insight into how planar defects in LPC‐Si thin films influence the device performance of the corresponding solar cells by acquiring electron‐backscatter diffraction maps and measuring solar cell parameters on the same identical positions. By this approach, it was possible to demonstrate how low scanning velocities of the laser line during the crystallization lead to lower densities of grain boundaries, to improved charge‐carrier diffusion lengths, and hence to improved device performances.
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CuNi binary alloy catalyst for growth of nitrogen‐doped graphene by low pressure chemical vapor deposition 下载免费PDF全文
Remi Papon Kamal P. Sharma Rakesh D. Mahayavanshi Subash Sharma Riteshkumar Vishwakarma Mohamad Saufi Rosmi Toshio Kawahara Joseph Cline Golap Kalita Masaki Tanemura 《固体物理学:研究快报》2016,10(10):749-752
The CuNi binary alloy can be significant as a catalyst for nitrogen‐doped (N‐doped) graphene growth considering controllable solubility of both carbon and nitrogen atoms. Here, we report for the first time the possibility of synthesizing substitutional N‐doped bilayer graphene on the binary alloy catalyst. Raman spectroscopy, atomic force microscopy and transmission electron microscopy analysis confirm the growth of bilayer and few‐layer graphene domains. X‐ray photoelectron spectroscopy analysis shows the presence of around 5.8 at% of nitrogen. Our finding shows that large N‐doped bilayer graphene domains can be synthesized on the CuNi binary alloy.