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1.
Pentacene thin‐film transistor with high‐κ TaLaO as gate dielectric has been fabricated and shows a carrier mobility of 0.73 cm2/V s, much higher than that based on pure La2O3 (0.43 cm2/V s) due to the smoother surface of the TaLaO film and thus larger pentacene islands grown on it in the initial stage. Moreover, among various times for fluorine‐plasma treatment on the TaLaO gate dielectric, 100 seconds result in the highest carrier mobility of 1.12 cm2/V s due to (1) smoothest oxide surface achieved by fluorine passivation of oxide traps, as measured by AFM and supported by smallest sub‐threshold swing and lowest low‐frequency noise; (2) the largest pentacene grains grown on the smoothest oxide surface, as demonstrated by AFM.
2.
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.
3.
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.
4.
Hidenobu Murata Yusuke Kataoka Tatsuya Kawamoto Isao Tanaka Takashi Taniguchi 《固体物理学:研究快报》2014,8(10):822-826
The α‐PbO2‐type TiO2 is synthesized under high‐pressure and high‐temperature environment and it shows higher photocatalytic activity as compared to rutile and anatase under UV irradiation. The reduction in α‐PbO2‐type TiO2 induces visible‐light photocatalytic activity. These results indicate that α‐PbO2‐type TiO2 is an important candidate material for use in a photocatalytic matrix.
5.
Polymer light‐emitting electrochemical cells (LECs) are two‐terminal, solid state devices with a mixed ionic/electronic conductor as the active layer. Once activated by a DC voltage or current, a doping‐induced homojunction dictates the electrical and optical response of the LEC, making it highly unique and attractive among organic devices. However, the depletion width, a fundamental parameter of any semiconductor homojunction, has never been determined experimentally for a static LEC junction. In this study, we apply spatially resolved photocurrent and photoluminescence (PL) scanning to an extremely large planar LEC that had been turned on to emit strongly then subsequently frozen. These concerted scanning and imaging studies depict a p–i–n junction structure in which the peak built‐in electric field lies at the interface between the intrinsic region and the p‐doped region. The corresponding 18 μm depletion width is very small compared to the 700 μm interelectrode spacing.
6.
Chen Hu Shuping Liu Mauro Fasoli Anna Vedda Martin Nikl Xiqi Feng Yubai Pan 《固体物理学:研究快报》2015,9(4):245-249
Electron traps are known to a have great influence on the carriers transport process in Ce based scintillators. On the other hand, the role of hole traps in the scintillation process has been less considered. By means of electron spin resonance (ESR), we detected hole traps in highly Ce‐doped LuAG:Ce,Mg ceramics in the form of σ‐type O– centers. The g ‐tensor components turn out to be g⊥ = 2.0103, and g|| = 2.0023, revealing the axial symmetry of these defects. Mg‐perturbed variants of O– centers are proposed to exist in LuAG:Ce,Mg. Their occurrence is related to an elongated Mg–O bond as evidenced by DFT calculations. Finally, the multiple role of O– centers in the scintillation process is discussed.
7.
High‐performance a‐Si1–xOx:H/c‐Si heterojunction solar cells realized by the a‐Si:H/a‐Si1–xOx:H stack buffer layer 下载免费PDF全文
We used amorphous silicon oxide (a‐Si1–xOx:H) and microcrystalline silicon oxide (µc‐Si1–xOx:H) as buffer layer and p‐type emitter layer, respectively, in n‐type silicon hetero‐junction (SHJ) solar cells. We proposed to insert a thin (2 nm) intrinsic amorphous silicon (a‐Si:H) thin film between the thin (2.5 nm) a‐Si1–xOx:H buffer layer and the p‐layer to form a stack buffer layer of a‐Si:H/a‐Si1–xOx:H. As a result, a high open‐circuit voltage (VOC) and a high fill factor (FF) were obtained at the same time. Finally, a high efficiency of 19.0% (JSC = 33.46 mA/cm2, VOC = 738 mV, FF = 77.0%) was achieved on a 100 μm thick polished wafer using the stack buffer layer.
8.
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.
9.
Investigation of strain‐induced phase transformation in ferroelectric transistor using metal‐nitride gate electrode 下载免费PDF全文
In this work, we report a ferroelectric memory with strained‐gate engineering. The memory window of the high strain case was improved by ~71% at the same ferroelectric thickness. The orthorhombic phase transition (from ferroelectric to anti‐ferroelectric transition) plays a key role in realizing negative capacitance effect at high gate electric field. Based on a reliable first principles calculation, we clarify that the gate strain accelerates the phase transformation from metastable monoclinic to orthorhombic and thus largely enhances the ferroelectric polarization without increasing dielectric thickness. This ferroelectric strain technology shows the potential for emerging device application.
10.
Jifeng Shao Zhongheng Liu Xiong Yao Li Pi Shun Tan Changjin Zhang Yuheng Zhang 《固体物理学:研究快报》2014,8(10):845-848
We report the synthesis of single‐phase Bi3O2S3 sample and confirm the occurrence of bulk superconductivity with transition temperature at 5.8 K. The Bi3O2S3 superconductor is categorized as typical type‐II superconductor based on the results of both temperature and magnetic field dependences of magnetization. Hall coefficient measurements give evidence of a multiband character, with a dominant conduction mainly by electron‐like charge carriers. The charge carrier density is about 1.45 × 1019 cm–3, suggesting that the system has very low charge carrier density.
11.
Device applications involving topological insulators (TIs) will require the development of scalable methods for fabricating TI samples with sub‐micron dimensions, high quality surfaces, and controlled compositions. Here we use Bi‐, Se‐, and Te‐bearing metalorganic precursors to synthesize TIs in the form of nanowires. Single crystal nanowires can be grown with compositions ranging from Bi2Se3 to Bi2Te3, including the ternary compound Bi2Te2Se. These high quality nanostructured TI compounds are suitable platforms for on‐going searches for Majorana fermions (Mourik et al., Science 336 , 1003 (2012) and Cook et al., Rev. B 86 , 155431 (2012) [1, 2]).
12.
Yu. Zorenko V. Gorbenko T. Zorenko O. Sidletskiy A. Fedorov P. Bilski A. Twardak 《固体物理学:研究快报》2015,9(8):489-493
We report for the first time the optimized content and excellent scintillation properties of single crystalline film (SCF) scintillators of multicomponent Gd3–xLux Al5–yGay O12:Ce garnet compounds grown by liquid phase epitaxy (LPE) method. The Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.75–2Ga2.25–3O12:Ce SCF show the light yield (LY) comparable with that of high‐quality bulk crystal analogues of these garnets but faster scintillation decay and very low thermoluminescence in the above room temperature range. To our knowledge, these SCF possess the highest LY values ever obtained in LPE grown garnet SCF scintillators exceeding by at least 1.5–1.6 times the values previously reported for SCF scintillators.
13.
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.
14.
Thomas Ratcliff Kean Chern Fong Avi Shalav Robert Elliman Andrew Blakers 《固体物理学:研究快报》2014,8(10):827-830
The selection of either an oxidising or inert ambient during high temperature annealing is shown to affect dopant activation and electron–hole recombination in boron implanted silicon samples. Samples implanted with B at fluence between 3 × 1014 cm–2 to 3 × 1015 cm–2 are shown to have lower dopant activation after oxidation at 1000 °C compared to an equivalent anneal in an inert ambient. In addition, emitter recombination is shown to be up to 15 times higher after oxidation compared with an inert anneal for samples with equivalent passivation from deposited Al2O3 films. The observed increase in recombination for oxidised samples is attributed to the enhanced formation of boron‐interstitial defect clusters and dislocation loops under oxidising conditions. It is also shown that an inert anneal for 10 minutes at 1000 °C prior to oxidation has no significant impact on sheet resistance or recombination compared with a standard oxidation process.
15.
We report on an elastic neutron scattering study of the charge correlations in La2–xSrx CoO4 with x = 1/3, 0.4 and 0.5. We found that the checkerboard charge ordering correlations present in the x = 0.5 sample persist in the x = 0.4 and 1/3 materials. These checkerboard charge ordering correlations are robust and explain the occurrence of nano‐phase separation in layered cobaltates for Sr‐concentrations away from half‐doping. The half‐integer reflections then arise from the nanometer‐sized hole‐rich regions (blue areas in title figure) instead of the undoped ones (red areas in title figure). The appearance of nano‐phase separation is an important ingredient for understanding the formation of hour‐glass shaped magnetic excitation spectra in La2–xSrx CoO4.
16.
Yang Zhang Huimin Zhang Yakui Weng Lingfang Lin Xiaoyan Yao Shuai Dong 《固体物理学:研究快报》2016,10(10):757-761
Superconductors and multiferroics are two of the hottest branches in condensed matter physics. The connections between those two fields are fundamentally meaningful to unify the physical rules of correlated electrons. Recently, BaFe2Se3, was predicted to be multiferroic [Phys. Rev. Lett. 113 , 187204 (2014)] due to its unique one‐dimensional block‐type antiferromagnetism. Here, another iron‐selenide KFe2Se2, a parent state of iron‐based superconductor, is predicted to be multiferroic. Its two‐dimensional block‐type antiferromagnetism can generate a moderate electric dipole for each Fe–Se layer via the Fe–Se–Fe exchange striction. Different stacking configurations of these magnetic blocks give closely proximate energies and thus the ground state of KFe2Se2 may be switchable between antiferroelectric and ferroelectric phases.
17.
Photo‐enhanced catalytic activity of spray‐coated Cu2SnSe3 nanoparticle counter electrode for dye‐sensitised solar cells 下载免费PDF全文
Soosaimanickam Ananthakumar Xuan Li Ann‐Louise Anderson Pelin Yilmaz Steve Dunn Sridharan Moorthy Babu Joe Briscoe 《固体物理学:研究快报》2016,10(10):739-744
Cu2SnSe3 nanoparticles are synthesised using oleylamine as both a solvent and capping agent and spray coated to form dye‐sensitised solar cell (DSSC) counter electrodes (CEs) using earth‐abundant elements. The film requires annealing at only 400 °C in nitrogen, which is a lower temperature than previous reports of both Cu2SnSe3and Cu2ZnSnSe4 films, also avoiding the use of Se gas. The composition and phase of the material is confirmed to be kesterite Cu2SnSe3. DSSCs using Cu2SnSe3 CEs give a power conversion efficiency of 4.87%, compared to 5.35% when using Pt. Electrochemical impedance spectroscopy indicates that the performance of the Cu2SnSe3 CE is enhanced under illumination, leading to a drop in the charge transfer resistance. This illumination‐induced enhancement of the catalytic activity provides a novel mechanism for the enhancement of CE performance in DSSCs.
18.
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.
19.
We found that non‐magnetic defects in two‐dimensional topological insulators induce bound states of two kinds for each spin orientation: electron‐ and hole‐like states. Depending on the sign of the defect potential these states can be also of two kinds with different distribution of the electron density. The density has a maximum or minimum in the center. A surprising effect caused by the topological order is a singular dependence of the bound‐state energy on the defect potential.
20.
Jiang Tang Jin Li Chaoyu He Chunxiao Zhang Tao Ouyang Chao Tang Huaping Xiao Jianxin Zhong 《固体物理学:研究快报》2017,11(3)
Silicene, a promising candidate for future electronic devices, has been fabricated only on supporting substrates as silicon atom prefers to form the sp3 hybridization structure. Therefore, it's important to search more stable two‐dimensional (2D) silicon allotropes and several 2D silicon allotropes have been proposed recently. In this work, we predict a new type of 2D silicon allotrope (called OTDS) based on ab initio structure, phonon‐mode and molecular dynamics calculations. OTDS has the in‐plane octagonal tiling (OT) pattern with dumbbell‐like structures and silicon atoms in OTDS are four‐ and three‐coordinated. OTDS is a semiconductor with a large band gap (about 1.5 eV by HSE calculation) and the band gap can be tuned effectively by the in‐plane strain.