共查询到20条相似文献,搜索用时 15 毫秒
1.
D. Massarotti B. Jouault V. Rouco G. Campagnano D. Giuliano P. Lucignano D. Stornaiuolo G. P. Pepe F. Lombardi F. Tafuri A. Tagliacozzo 《Journal of Superconductivity and Novel Magnetism》2017,30(1):5-14
Coplanar Al/graphene/Al junctions fabricated on the same graphene sheet deposited on silicon carbide (SiC), show robust Josephson coupling at subKelvin temperature, when the separations between the electrodes is below 400 nm. Remarkably, a hysteretic Critical State sets in when ramping an orthogonal magnetic field, with a sudden collapse of the Josephson critical current I c when turning the field on, and a revival of I c when inverting the sweep. Similar hysteresis can be found in granular superconducting films which may undergo the Berezinskii-Kosterlitz-Thouless transition. Here, we give quantitative arguments to prove that this odd behavior of the magnetoconductance gives evidence for an incipient Berezinskii-Kosterlitz-Thouless transition with drift and pinning of fluctuating free vortices induced by the current bias. 相似文献
2.
Prins F Barreiro A Ruitenberg JW Seldenthuis JS Aliaga-Alcalde N Vandersypen LM van der Zant HS 《Nano letters》2011,11(11):4607-4611
We report on a method to fabricate and measure gateable molecular junctions that are stable at room temperature. The devices are made by depositing molecules inside a few-layer graphene nanogap, formed by feedback controlled electroburning. The gaps have separations on the order of 1-2 nm as estimated from a Simmons model for tunneling. The molecular junctions display gateable I-V-characteristics at room temperature. 相似文献
3.
Tatnatchai Suwannasit I-Ming Tang Rassmidara Hoonsawat Bumned Soodchomshom 《Journal of Low Temperature Physics》2011,165(1-2):15-26
The Josephson effect in a gapped graphene-based superconductor/barrier/superconductor junction is studied. The superconductivity in gapped graphene may be achieved by depositing conventional superconductor on the top of the gapped graphene such as graphene grown on SiC substrate. In gapped graphene system, the carriers exhibit massive Dirac fermions. We focus on the effect of pseudo-Dirac-like mass on the supercurrent. In contrast to that in the gapless graphene superconductor/barrier/superconductor junction, we find that the supercurrent exhibits dependency of the Fermi energy. Also, the massive supercurrent anomalously oscillates as a function of the gate potential. This novel behavior is due to the effect of electrons acquiring mass in gapped graphene. 相似文献
4.
The authors fabricated Y-Ba-Cu-O/Au/AlOx/Nb and Y-Ba-Cu-O/AlOx/Nb Josephson tunnel junctions using electron-beam evaporation of Al and Nb films and natural oxidation. Sintered Y-Ba-Cu-O was used as the base electrode. Superconducting Josephson current and hysteresis of the current-voltage characteristics, which are typical features of Josephson tunnel junctions, have been observed at 4.2 K. RF-induced voltage steps at a voltage greater than 0.4 mV have been clearly observed, and RF-induced subharmonic steps have also appeared. The superconducting Josephson current was modulated by the magnetic field 相似文献
5.
Anne W. Draelos Ming Tso Wei Andrew Seredinski Chung Ting Ke Yash Mehta Russell Chamberlain Kenji Watanabe Takashi Taniguchi Michihisa Yamamoto Seigo Tarucha Ivan V. Borzenets François Amet Gleb Finkelstein 《Journal of Low Temperature Physics》2018,191(5-6):288-300
In this study, we examine multiple encapsulated graphene Josephson junctions to determine which mechanisms may be responsible for the supercurrent observed in the quantum Hall (QH) regime. Rectangular junctions with various widths and lengths were studied to identify which parameters affect the occurrence of QH supercurrent. We also studied additional samples where the graphene region is extended beyond the contacts on one side, making that edge of the mesa significantly longer than the opposite edge. This is done in order to distinguish two potential mechanisms: (a) supercurrents independently flowing along both non-contacted edges of graphene mesa, and (b) opposite sides of the mesa being coupled by hybrid electron–hole modes flowing along the superconductor/graphene boundary. The supercurrent appears suppressed in extended junctions, suggesting the latter mechanism. 相似文献
6.
Xiaochun Huang Bing Liu Jiaqi Guan Guangyao Miao Zijian Lin Qichang An Xuetao Zhu Weihua Wang Jiandong Guo 《Advanced materials (Deerfield Beach, Fla.)》2018,30(30)
Two‐dimensional (2D) in‐plane p–n junctions with a continuous interface have great potential in next‐generation devices. To date, the general fabrication strategies rely on lateral epitaxial growth of p‐ and n‐type 2D semiconductors. An in‐plane p–n junction is fabricated with homogeneous monolayer Te at the step edge on graphene/6H‐SiC(0001). Scanning tunneling spectroscopy reveals that Te on the terrace of trilayer graphene is p‐type, and it is n‐type on monolayer graphene. Atomic‐resolution images demonstrate the continuous lattice of the junction, and mappings of the electronic states visualize the type‐II band bending across the space‐charge region of 6.2 nm with a build‐in field of 4 × 105 V cm?1. The reported strategy can be extended to other 2D semiconductors on patternable substrates for designed fabrication of in‐plane junctions. 相似文献
7.
In this work, the features of graphene layers are studied with the aim of preparing the thinnest layers possible. The graphene layers were prepared by the annealing of Ni/SiC structures. The main advantage of this process is a relatively low temperature compared with the method of graphene epitaxial growth on SiC and short annealing times compared with the chemical vapor deposition method. We prepared graphene layers from several Ni/SiC structures in which the Ni layer thickness ranged from 1 to 200 nm. The parameters of the annealing process (temperature, rate of temperature increase, annealing time) were modified during the experiments. The formed graphene layers were analyzed by means of Raman spectroscopy. From the spectra, the basic parameters of graphene, such as the number of carbon layers and crystallinity, were determined. The annealing of the Ni(200 nm)/SiC structure at 1080 °C for 10 s, produced graphene in the form of 3-4 carbon monolayers. The value was verified by X-ray Photoelectron Spectroscopy (XPS). Good agreement was achieved in the results obtained using Raman spectroscopy and XPS. 相似文献
8.
研究了用微米级Ti3SiC2 陶瓷颗粒与Al 粉复合球磨制备纳米复合材料的工艺过程。结果表明, 在其他实验参数相同的条件下, 不同材质的磨球对陶瓷颗粒的细化作用差异很大。采用氧化锆磨球可以使Ti3SiC2 的颗粒更好地细化且均匀分散在Al 基体中, 而用钢球和玛瑙球则易产生混合粉的团聚。用氧化锆球进行球磨后的复合粉在550 ℃的温度及20 MPa 的压力下成功地制备了组织成分均匀的大块纳米复合材料。与同成分的非纳米材料相比, Ti3SiC2 / Al 纳米复合材料的硬度从HV60 提高到HV80 , 强度则从110 MPa 提高到150 MPa 。 相似文献
9.
A. Potts P. R. Routley G. J. Parker J. J. Baumberg P. A. J. de Groot 《Journal of Materials Science: Materials in Electronics》2001,12(4-6):289-293
Novel processes for the fabrication of mesoscopic Josephson junction qubits have been developed, based on superconducting Al/Al2O3/Al tunnel junctions. These are fabricated by electron beam lithography using single-layer and multi-layer resists, and standard processes that are compatible with conventional CMOS processing. The new single-layer resist process is found to have significant advantages over conventional fabrication methods using suspended tri-layer shadow masks. 相似文献
10.
Using DFT-based calculations, we study chemical doping of silicene–graphene hybrid with (B, N, Al and P). Planar structure of SiC sheet remains unaffected on doping and all the systems are stable. P and N dopants are strongly bonded to the hybrid compared with Al and N. Charge transfer calculations show that (B, N)/(Al, P) behave like acceptors/donors, respectively. All configurations retain the semi-conductor character of pure SiC and show magnetic order. Curie temperature is determined for the ferromagnetic structures. These results provide the possibility of tuning the gap and inducing magnetism in SiC as required for future applications. 相似文献
11.
12.
Reinhold Kleiner 《Journal of Low Temperature Physics》1997,106(3-4):453-462
The high temperature superconductors form natural superconducting multilayers where adjacent superconducting layers are weakly
coupled by the Josephson effect. As a consequence, single crystals act intrinsically as vertical stacks of Josephson junctions.
At present, intrinsic Josephson junctions are fabricated and investigated by several groups. There has been considerable progress
both in production of high quality junctions and in theoretical understanding of the intrinsic Josephson effect. In this paper
the basic physics of intrinsic Josephson junctions is outlined. Some examples of the present status of research are given. 相似文献
13.
高分子材料的绝热特性极大地限制了其作为导热材料在工业中的应用。选用多层石墨烯作为导热填料,并分别与导热填料氧化铝(Al_2O_3)和碳化硅(SiC)复配,探究导热填料的复配对尼龙6(PA6)复合材料导热性能的影响。加入质量分数为3%石墨烯时,PA6复合材料的热导率为0.548W·m-1·K-1,相比PA6基体提高161%。通过调节石墨烯与Al_2O_3和SiC复配的比例以及复合填料量,PA6复合材料的热导率可控在0.653~4.307W·m-1·K-1之间,最高是PA6基体的20倍。为拓展石墨烯在导热材料方面的应用及PA6导热材料在工业上应用提供了有价值的实验依据。 相似文献
14.
《IEEE transactions on instrumentation and measurement》2009,58(4):797-802
15.
16.
Petr Macháč Tomáš Fidler Stanislav Cichoň Vlastimil Jurka 《Journal of Materials Science: Materials in Electronics》2013,24(10):3793-3799
Bi-layer graphene sheets have been prepared on the basis of a reaction of cobalt with silicon carbide at temperatures around 1,000 °C. This is a type of viable low temperature graphene synthesis. Preparation of graphene was carried out with various thicknesses of the Co layer deposited onto the SiC surface and parameters of the annealing process (temperature, annealing time) were varied. Number of carbon mono-layers in the prepared graphene and its crystallinity were determined from the results of Raman spectroscopy. The best results have been obtained for a structure with Cobalt layer of 300 nm thickness, annealed at 1,080 °C for the period of 120 s. When using shorter annealing times, significantly non-homogenous reaction of Co with SiC has been observed, forming two different phases on the surface. 相似文献
17.
I. N. Askerzade 《Technical Physics Letters》2004,30(10):857-858
The process of thermal activation in the tunnel Josephson junctions simultaneously carrying both constant (dc) and alternating
(ac) currents has been studied. The presence of the ac component leads to a decrease in the potential barrier for a metastable
state of the Josephson junction. The thermal activation threshold is expressed as a function of the ac current amplitude.
The results agree with the data of recent experiments on the statistics of switching from a superconducting to resistive state
in the Josephson tunneling junctions. 相似文献
18.
Benz S.P. Dresselhaus P.D. Burroughs C.J. Jr. 《IEEE transactions on instrumentation and measurement》2001,50(6):1513-1518
We have developed two voltage standard systems: 1) the programmable Josephson voltage standard and 2) the Josephson arbitrary waveform synthesizer. The programmable system is fully automated and provides stable programmable dc voltages from -1.2 V to +1.2 V. The synthesizer is the first quantum-based ac voltage standard source. It uses perfectly quantized Josephson pulses to generate arbitrary waveforms with low harmonic distortion and stable, calculable time-dependent voltages. Both systems are presently limited to output voltages less than 10 V as a result of frequency requirements and the limits of junction fabrication technology. We describe the development of fabrication technology for these systems and describe the circuit- and fabrication-related constraints that presently limit system performance. Finally, we propose the use of lumped arrays of junctions to achieve higher practical voltages through development of a nanoscale junction technology, in which 13 000 junctions are closely spaced at 50 nm-100 nm intervals 相似文献
19.
Anomaly in Fabrication Processes for Large-Scale Array Detectors of Superconducting Tunnel Junctions
M. Ukibe Y. Chen Y. Shimizugawa Y. Kobayashi A. Kurokawa M. Ohkubo 《Journal of Low Temperature Physics》2008,151(1-2):316-321
The STJ array detectors with an effective detection area of 4 mm2, which consist of 100 Nb/Al-AlOx/Al/Nb junctions with a size of 200×200 μm, have been fabricated. In order to improve the
reproducibility of the STJ array fabrication, we investigated a correlation between the junction surface structures and the
leakage currents. It has been found that the junctions near the fringe of the array detectors have a step of about 5 nm at
the middle of the array detector, of which leakage currents are considerably larger than 1 μA. The step structure was formed
after the etching of the bottom Nb layer for complete separation of Nb/Al/AlOx/Al/Nb/Si. In case of the sputtered Nb/Al/Nb/Si
multilayers without 1 nm-thick tunneling barrier, no stepped surface was observed even after the bottom Nb layer etching.
Therefore, it is apparent that the 5 nm step structure is a cause of the large leakage currents. We solved the step-fringe
problem by a kind of extra patterning along the fringe of the array or lift-off patterning of the Nb/Al multilayers. It is
concluded that the number of the junctions with the step structure depends on a slight difference in film deposition or etching
conditions.
相似文献
20.
Kohlmann J. Schulze H. Behr R. Muller F. Niemeyer J. 《IEEE transactions on instrumentation and measurement》2001,50(2):192-194
A programmable dc voltage standard for output voltages of up to 10 V has been realized. The series arrays, consisting of about 69120 overdamped superconductor/insulator/normal metal/insulator/superconductor (SINIS) Josephson junctions, have been fabricated using the reliable Nb-Al/Al2O3 technology. The arrays can be operated in conventional Josephson voltage standards at microwave frequencies from 70 GHz to 75 GHz. Steps of constant voltage are observed at very low microwave power levels, since the major part of the microwave power is generated by the junctions themselves. The operation of the arrays and the formation of Shapiro steps are discussed 相似文献