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1.
《Applied Superconductivity》1997,5(1-6):27-31
We report growth of Bi2Sr2CaCu2O8+δ single crystals with dimensions of 6×2×0.03 mm3 using a melt and growth technique. The oxygen content is determined to be δ≈0.13 by iodometric titration. The crystal is shown to be homogeneous and close to stoichiometric cation ratio. The superconducting temperature with a sharp transition width (10–90% level) of 6–8 K was determined to be Tc=92 K from resistivity and dc susceptibility measurements. The predominant impurity phase is a Cu-free crystal, whose composition is identified as Bi10Sr11Ca5Ox. The crystal structure of Bi10Sr11Ca5Ox is monoclinic with a=11.108(1) Å, b=5.9487(1) Å; c=19.838 (3) Åand β=101.5° (P21/c space group). 相似文献
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3.
《Applied Superconductivity》1999,6(10-12):759-765
We report our studies on light-induced changes in electrical properties of YBa2Cu3Ox (YBCO) grain-boundary Josephson weak links. We discuss the erasable process (photodoping), in which light-induced enhancement of junctions properties at low temperatures relaxes back above 250 K. Our studies are focused on the junction critical current versus time, light intensity, and magnetic field measurements. In tested few-μm-wide step-edge junctions, photodoping manifested itself as above 50% increase of the critical current and the decrease of the junction magnetic penetration depth, leading to reduction of the effective junction width. Contrary to the photodoping effect, the high-intensity laser modification of junctions led to permanent modification of their electrical characteristics that remained unchanged after subsequent room-temperature/helium thermal cycling of the sample. The laser-modified junctions exhibited up to 25% increase of the critical current times normal-state resistance product. 相似文献
4.
G. F. Novikov M. V. Gapanovich V. F. Gremenok K. V. Bocharov W. -T. Tsai Ming-Jer Jeng Liann-Be Chang 《Semiconductors》2017,51(1):18-22
The method of time-resolved microwave photoconductivity at a frequency of 36 GHz in the range of temperatures of 200–300 K is used to study the kinetics of the annihilation of charge carriers in Cu–Zn–Sn–Se powders obtained by the solid-phase method of synthesis in cells. The lifetime of excess electrons at room temperature is found to be shorter than 5 ns. The activation energy for the process of recombination amounted to E a ~ 0.054 eV. 相似文献
5.
Metal–insulator–semiconductor Schottky diodes were fabricated to investigate the tunnel effect and the dominant carrier transport mechanism by using current density–voltage (J–V) and capacitance–voltage (C–V) measurements in the temperature range of 295–370?K. The slope of the ln?J–V curves was almost constant value over the nearly four decades of current and the forward bias current density J is found to be proportional to Jo (T) exp(AV). The values of Nss estimated from J–V and C–V measurements decreased with increasing temperature. The temperature dependence of the barrier heights obtained from forward bias J–V was found to be entirely different than that from the reverse bias C–V characteristics. All these behaviours confirmed that the prepared samples have a tunnel effect and the current transport mechanism in the temperature range of 295–370?K was predominated by a trap-assisted multi-step tunnelling, although the Si wafer has low doping concentration and the measurements were made at moderate temperature. 相似文献
6.
The results are reported of a detailed investigation into the photoinduced changes that occur in the capacitance–voltage (C–V) response of an organic metal–insulator–semiconductor (MIS) capacitor based on the organic semiconductor poly(3-hexylthiophene), P3HT. During the forward voltage sweep, the device is driven into deep depletion but stabilizes at a voltage-independent minimum capacitance, Cmin, whose value depends on photon energy, light intensity and voltage ramp rate. On reversing the voltage sweep, strong hysteresis is observed owing to a positive shift in the flatband voltage, VFB, of the device. A theoretical quasi-static model is developed in which it is assumed that electrons photogenerated in the semiconductor depletion region escape geminate recombination following the Onsager model. These electrons then drift to the P3HT/insulator interface where they become deeply trapped thus effecting a positive shift in VFB. By choosing appropriate values for the only disposable parameter in the model, an excellent fit is obtained to the experimental Cmin, from which we extract values for the zero-field quantum yield of photoelectrons in P3HT that are of similar magnitude, 10?5 to 10?3, to those previously deduced for π-conjugated polymers from photoconduction measurements. From the observed hysteresis we deduce that the interfacial electron trap density probably exceeds 1016 m?2. Evidence is presented suggesting that the ratio of free to trapped electrons at the interface depends on the insulator used for fabricating the device. 相似文献
7.
The GLV method of Gallant, Lambert, and Vanstone (CRYPTO 2001) computes any multiple kP of a point P of prime order n lying on an elliptic curve with a low-degree endomorphism Φ (called GLV curve) over $\mathbb{F}_{p}$ as $$kP = k_1P + k_2\varPhi(P) \quad\text{with } \max \bigl\{ |k_1|,|k_2| \bigr\} \leq C_1\sqrt{n} $$ for some explicit constant C 1>0. Recently, Galbraith, Lin, and Scott (EUROCRYPT 2009) extended this method to all curves over $\mathbb{F}_{p^{2}}$ which are twists of curves defined over $\mathbb{F}_{p}$ . We show in this work how to merge the two approaches in order to get, for twists of any GLV curve over $\mathbb{F}_{p^{2}}$ , a four-dimensional decomposition together with fast endomorphisms Φ,Ψ over $\mathbb{F}_{p^{2}}$ acting on the group generated by a point P of prime order n, resulting in a proven decomposition for any scalar k∈[1,n] given by $$kP=k_1P+ k_2\varPhi(P)+ k_3\varPsi(P) + k_4\varPsi\varPhi(P) \quad \text{with } \max_i \bigl(|k_i| \bigr)< C_2\, n^{1/4} $$ for some explicit C 2>0. Remarkably, taking the best C 1,C 2, we obtain C 2/C 1<412, independently of the curve, ensuring in theory an almost constant relative speedup. In practice, our experiments reveal that the use of the merged GLV–GLS approach supports a scalar multiplication that runs up to 1.5 times faster than the original GLV method. We then improve this performance even further by exploiting the Twisted Edwards model and show that curves originally slower may become extremely efficient on this model. In addition, we analyze the performance of the method on a multicore setting and describe how to efficiently protect GLV-based scalar multiplication against several side-channel attacks. Our implementations improve the state-of-the-art performance of scalar multiplication on elliptic curves over large prime characteristic fields for a variety of scenarios including side-channel protected and unprotected cases with sequential and multicore execution. 相似文献
8.
Zhigalina O. M. Burmistrova P. V. Vasil'ev A. L. Roddatis V. V. Vorotilov K. A. Sigov A. S. 《Russian Microelectronics》2001,30(3):175-178
Model Si–SiO2–Ti–Pt–PZT multilayer structures obtained by chemical solution deposition at excessive (relative to the stoichiometric composition) amounts of lead in the starting film-forming solution (x= 0–30 mol %) were studied by TEM and X-ray microanalysis techniques. In the absence of excessive lead, the films crystallize largely into the metastable phase of pyrochlore, which does not have ferroelectric properties. With an excessive amount of lead added, PZT ceramic crystallizes into the ferroelectric phase of perovskite and has columnar grains 0.2 m in size. The thermal stability of the metallization system during the formation of the ferroelectric film was investigated. A 180-nm-thick transition layer between the Pt electrode and the adhesive titanium film was discovered. This layer, resulting from high-temperature synthesis, consists of fine-grain platinum, as well as metal oxides and silicides. 相似文献
9.
Vasiliev A. G. Zakharov R. A. Rodatis V. V. Lobintsov A. V. Orlikovskii A. A. Horin I. A. 《Russian Microelectronics》2001,30(5):295-302
The kinetics of phase formation in Ti–Co–Si–N and Ti–Co–N thin films on Si and SiO2is investigated experimentally. With the deposition on Si, rapid thermal annealing (T 900°C) is shown to cause phase separation that ends in a TiN/CoSi2/Si structure. If SiO2is used, the alloy reacts with the substrate to produce compounds that are difficult to remove with selective etchants. This limits the potential uses of this process in the fabrication of contact systems for CMOS devices. It is shown that structure- and phase-dissimilar films can be formed on Si and SiO2by means of the surface-diffusion reactions between a Ti–Co–Si–N or Ti–Co–N alloy and the substrate at 650–700°C. The effect of a TiN, Ti, or CoSi2thin layer at the alloy–substrate interface on the phase separation is investigated. 相似文献
10.
Usanov D. A. Nikitov S. A. Skripal’ A. V. Merdanov M. K. Evteev S. G. Ponomarev D. V. 《Journal of Communications Technology and Electronics》2019,64(4):399-408
Journal of Communications Technology and Electronics - A feasible design of a system with an allowed band with near-unity frequency-independent transmission utilizing the reflective properties of... 相似文献
11.
Donor–acceptor–acceptor–donor small molecules for solution processed bulk heterojunction solar cells
We report on the optical and electrochemical characterization (experimental and theoretical) of two donor substituted benzothiadiazole with different cyano based acceptor π-linkers, tetracyanobutadiene (TCBD) SM1 and dicyanoquinomethane (DCNQ) SM2, and explore them as the donor component for solution processed bulk heterojunction organic solar cells, along with PC71BM as the electron acceptor. The solution bulk heterojunction (BHJ) solar cells based on dichloromethane (DCM) processed active layer with SM1 and SM2 as donor and PC71BM as acceptor achieve power conversion efficiency (PCE) of 2.76% and 3.61%, respectively. The solar cells based on these two small molecules exhibit good Voc, which is attributed to their deep HOMO energy level. The higher PCE of the device based on SM2 compared to SM1 is attributed to the its small bandgap, broader absorption profile and enhanced hole mobility. Additionally, the PCE of the SM2:PC71BM based solar cells processed with 1-chloronaphthalene CN (3 v%)/DCM is further improved reaching upto 4.86%. This increase in PCE has been attributed to the improved nanoscale morphology and more balanced charge transport in the device, due to the solvent additive. 相似文献
12.
L. Brigo A. Pistore G. Grenci A. Carpentiero F. Romanato G. Brusatin 《Microelectronic Engineering》2010,87(5-8):947-950
The direct nanopatterning of a novel hybrid organic–inorganic sol–gel film based on bridged polysilsesquioxanes (BPS) using X-ray synchrotron radiation is reported. The main advantages of a direct fabrication technique with respect to conventional photolithography are represented by the possibility to bypass some typical post-exposure lithographic steps and to avoid the use of a sacrificial layer. The distinctive features rendering hybrid BPS-based material innovative for photolithographic applications are: the patternability as resist, the positive tone behaviour exhibited under X-ray irradiation, the porous structure demonstrated at low temperature, and the possibility to widely tailor material electro-optical and structural properties to experimental needs. A systematic investigation of the interactions between sol–gel BPS films based on the bis(triethoxysilyl)benzene precursor and soft X-rays is conducted. Under X-ray exposure, BPS-based films suffer structural changes attributed to the organic bridge breaking, and become soluble in suitable acidic aqueous solutions, producing final lithographies of sub-micron resolution, high contrast and good edge definition. 相似文献
13.
Xue Chen Bingkun Chen Bei Jiang Tengfei Gao Gang Shang Su-Ting Han Chi-Ching Kuo Vellaisamy A. L. Roy Ye Zhou 《Advanced functional materials》2023,33(1):2208807
Simulating biological synaptic functionalities through artificial synaptic devices opens up an innovative way to overcome the von Neumann bottleneck at the device level. Artificial optoelectronic synapses provide a non-contact method to operate the devices and overcome the shortcomings of electrical synaptic devices. With the advantages of high photoelectric conversion efficiency, adjustable light absorption coefficient, and broad spectral range, nanowires (NWs)-based optoelectronic synapses have attracted wide attention. Herein, to better promote the applications of nanowires-based optoelectronic synapses for future neuromorphic systems, the functionalities of optoelectronic synaptic devices and the current progress of NWs optoelectronic synaptic devices in UV–vis–IR spectral range are introduced. Furthermore, a bridge between NWs-based optoelectronic synaptic device and the neuromorphic system is established. Challenges for the forthcoming development of NWs optoelectronic synapses are also discussed. This review may offer a vision into the design and neuromorphic applications of NWs-based optoelectronic synaptic devices. 相似文献
14.
D. Kannadassan R. Karthik Maryam Shojaei Baghini P.S. Mallick 《Materials Science in Semiconductor Processing》2013,16(2):274-281
This paper presents fabrication and electrical characterization of barrier type TiO2 metal–insulator–metal (MIM) capacitor using anodization. Polarization process, conduction mechanisms, and structural properties are studied in detail. We found that the anodization voltage played a major role in electrical and structural properties of the thin film. The barrier type anodic TiO2 is suggested as a dielectric material for high-performance MIM capacitors. 相似文献
15.
K. Kitagawa T. Aoki S. Khunkhao Y. Wongprasert W. Titiroongruang K. Sato 《International Journal of Electronics》2013,100(10):595-600
Optical-beam profiling properties of Schottky-barrier metal–semiconductor–metal (MSM) structures have been investigated experimentally. Making use of a planar molybdenum/n-type silicon/molybdenum (Mo/n-Si/Mo) MSM structure with a wide electrode separation, one-dimensional (1-D) profiling of optical-beam intensity distribution from a helium–neon (He–Ne) laser was carried out. It was confirmed that, in addition to the existing photosensing function, the sensitivity (output photocurrent) of such a structure could be controlled by applying a bias via lateral spreading of the surface space-charge-region (SCR) at the side of the reverse-biased Schottky-junction. 相似文献
16.
Yinjiang Liu Tao Liu Xi Guo Meichen Hou Yihui Yuan Se Shi Hui Wang Rui-Zhi Zhang Costas Galiotis Ning Wang 《Advanced functional materials》2023,33(3):2210028
As the power-conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long-term ambient stability. Here, the application of PCN-224 quantum dots (QDs) is reported, a typical Zr-based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN-224 QDs with abundant Lewis-base groups (e.g., CO, C−N, CN) contribute to high-quality perovskite films with enlarged grain size and reduced defect density by interaction with under-coordinated Pb2+. Meanwhile, PCN-224 QDs enable the well-matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN-224 QDs-treated HTL can capture Li+ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li-TFSI. Moreover, PCN-224 QDs mitigated Li+ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs. 相似文献
17.
This article deals with a ring–mesh network design problem arising from the deployment of an optical transport network. The
problem seeks to partition the set of demand pairs to a number of rings and a mesh cluster, and to determine the location
of the optical cross-connect system (OXC), while minimizing the total cost of optical add-drop multiplexers (OADMs), OXCs,
and fiber links. We formulate this problem as a zero-one integer programming problem. In strengthening the formulation, we
develop some valid inequalities for the zero-one quadratic (knapsack) polytope and a column generation formulation that eliminates
the symmetry of ring configurations. Also, we prescribe an effective tabu search procedure for finding a good quality feasible
solution, which is also used as a starting column for the column generation procedure. Computational results show that the
proposed solution procedure provides tight lower and upper bounds within a reasonable time bound. 相似文献
18.
Ivchenko E. L. Kalevich V. K. Kunold A. Balocchi A. Marie X. Amand T. 《Semiconductors》2019,53(9):1175-1181
Semiconductors - Experimental and theoretical studies on optical orientation and spin-dependent recombination in a semiconductor in a magnetic field under the normal incidence of circularly... 相似文献
19.
K. Jagannadham 《Journal of Electronic Materials》2011,40(1):25-34
Samples of graphene composites with a matrix of indium or indium-gallium alloy were prepared in the form of foils using exfoliated
graphene dispersions. The thermal conductivity of the composite samples with different thicknesses was determined using the
three-omega method. Indium–graphene composite samples with a thickness of 430 μm exhibited a twofold increase in thermal conductivity, whereas indium-gallium–graphene composite samples with a thickness
of 330 μm exhibited a threefold improvement in thermal conductivity over that of the matrix at 300 K. The effective medium approximation
(EMA) was used to model the thermal conductivity of the composite samples. The graphene platelet size distribution was used
to determine the average thermal conductivity of graphene in the composite samples. The interfacial thermal conductance between
graphene and indium or indium-gallium alloy determined from EMA was not the limiting factor in the improvement of the thermal
conductivity of the composite samples, although the increase in thermal conductivity was found to be slightly lower than predicted
theoretically using acoustic and diffuse mismatch models. The smaller size of the graphene platelets obtained by exfoliation
prior to dispersion in the matrix appears to be the limiting factor. 相似文献
20.
《Applied Superconductivity》1999,6(10-12):809-815
Microwave properties of YBa2Cu3O7-δ (YBCO) films grown on (100) LaAlO3 (LAO), (110) NdGaO3 (NGO) and (001) SrLaAlO4 (SLAO) substrates were studied in the form of a microstrip ring resonator at temperatures above 20 K. The YBCO resonator on a SLAO substrate showed microwave properties better than or comparable to other YBCO resonators on LAO substrates. For the YBCO resonators on LAO and SLAO substrates, both QU and f0 appeared to decrease as the temperature was raised. Meanwhile the resonator on a NGO substrate showed different behaviors with QU showing a peak at ∼70 K, which are attributed to the unique temperature dependence of the loss tangent of the NGO substrate. An X-band oscillator with a YBCO ring resonator coupled to the circuit was prepared and its properties were investigated at low temperatures. The frequency of the oscillator signal appeared to change from 7.925 GHz at 30 K to 7.878 GHz at 77 K, which was mostly attributed to the change in f0 of the YBCO ring resonator. The signal power appeared to be more than 4.5 mW at 30 K and 2.1 mW at 77 K, respectively. At 55 K, the frequency of the oscillator signal was 7.917 GHz with the 3 dB-linewidth of 450 Hz. 相似文献