NbN/AlN/NbN超导隧道结的制备工艺

研究了在MgO基片上制备NbN/AlN/NbN结的工艺,NbN和AlN的制备分别采用直流磁控溅射和交流磁控溅射。为了得到良好特性的隧道结,首先要在高真空反应室里沉积三层膜结构,经过光刻和反应离子刻蚀,得到底电极和桥区的三层结构图形。再经过第二步光刻和刻蚀,仅保留底电极最下层的NbN,得到结区的三层结构图形,并覆盖AlN绝缘层。经过Lift-off工艺,洗去结区上的光刻胶,最后沉积上电极。使用四端子方法对制备的隧道结进行了一系列测量,特别是在高频(THz)下的响应。     

One-dimensional chain structure based on bifurcated hydrogen bonding

The structure of complex [PyH][Ni(mnt)₂], as determined by X-ray single crystal analysis, consists of pyridinium cations and [Ni(mnt)₂]^– anions. Crystallographic data for the complex: monoclinic P2₁/c, a = 16.5430(18) Å, b = 6.3847(9) Å, c = 17.430(2) Å, = 118.040(7)°, V = 1625.4(3) ų, Z = 4. The [Ni(mnt)₂]^– anion is not a planar and the CN groups bend away from the S₄ plane. The interactions between anions and cations via the formation of bifurcated N–H···NC hydrogen bonds give rise to an 1D zigzag chain of alternating cations and anions.     

Al/AlO_x/Al超导隧道结的制备工艺研究

研究了在高阻硅衬底上Al/AlO x/Al隧道结的制备技术,采用电子束蒸发制备Al/AlO x/Al三层材料,湿法刻蚀制备底电极和上电极以及电路连线,PECVD法生长绝缘层(SiO2)保护超导隧道结,RIE刻蚀上电极窗口。在400mK温度下测量了Al/AlO x/Al隧道结样品,得到了较好的隧道结I-V曲线,能隙电压Vg为0.325mV,超导临界电流I c为55nA,漏电流为5nA。     

A multi-functional superconductor single-photon detector at telecommunication wavelength

A multi-functional single-photon detector was demonstrated to resolve photon states by multiple superconductor single photon detectors (SSPDs) system with improved readout settings. The photon number and space distribution were resolved simultaneously by the presented system, which inherits the merits of SSPD, such as wide-response band, high repetition rate and working stability. Experimentally, four photons were resolved and the photon distribution over three pixels was figured out according to the amplitudes of output pulses at the telecommunication wavelength. The extension of this proposal to incorporate more elements for resolving more photons and revealing photons spatial distribution over larger scale is also discussed.     

High-T c superconducting thin film/GaAs MESFET hybrid microwave oscillator

A high-T _c superconducting (HTSC) thin film/GaAs MESFET hybrid microwave oscillator operated at 10.6 GHz has been designed, fabricated and characterized. Microstrip line structures were used throughout the circuit with superconducting thin film YBa₂Cu₃O_7-δ(YBCO) as the conductor material. The YBCO thin films were deposited on 15 mm×10 mm×0.5 mm LaAlO₃ substrates. The oscillator was common-source, series feedback type using a GaAs-MESFET (NE72084) as the active device and a superconducting microstrip resonator as the frequency stabilizing element. By improving the unloaded quality factorQ ₀ of the superconducting microstrip resonator and adjusting the coupling coefficient between the resonator and the gate of the MESFET, the phase noise of the oscillator was decreased. At 77 K, the phase noise of the oscillator at 10 kHz offset from carrier was −87 dBc/Hz. Project supported by the National Center for Research and Development on Superconductivity of China.     

Al/Al_2O_3/Al隧道结相位扩散的现象

超导约瑟夫森结是超导量子比特的核心元件,由约瑟夫森结组成的直流超导量子干涉器(DC-SQUID)由于其具有较高的探磁灵敏度,在超导磁通量子比特量子位测量中具有重要的作用.我们用铝为超导材料,采用电子束斜蒸发及静态氧化的方法制备了由两个Al/Al2O3/Al隧道结并联组成的DC-SQUID样品.将DC-SQUID样品置于20~1000mK范围内的不同温度下,对其跳变电流分布进行了测量.在50mK明显观测到了隧道结跳变电流机制由宏观量子隧穿到热激发的转变,并且在高于80mK时,观测到了相位扩散的现象.这对于隧道结相位动力学研究具有重要意义.     

The Effect of Oligo(Ethylene Oxide) Side Chains: A Strategy to Improve Contrast and Switching Speed in Electrochromic Polymers

Solution-processable electrochromic polymers (ECPs) with high performance are urgently needed for extensive applications. Nevertheless, they suffer from slow switching speed because of low ionic conductivities. Herein, we present an effective strategy to improve the contrast and switching speed in ECPs via facile side-chain engineering. A novel electrochromic thieno[3,2-b]thiophene-based polymer (PmOTTBTD) is designed and successfully synthesized by introducing oligo(ethylene oxide) side chains with high ionic conductivity. Compared to the counterpart POTTBTD without modification by oligo(ethylene oxide) chains, PmOTTBTD demonstrates nearly double contrast (42 % vs. 24 %) with a fast oxidation switching process that just takes half of the time when detected under 400 nm, as well as much higher coloration efficiencies (e. g. 239.04 cm² C⁻¹ vs. 226.26 cm² C⁻¹ @ 400 nm and 314.04 cm² C⁻¹ vs. 174.00 cm² C⁻¹ @ 650∼700 nm). Besides, PmOTTBTD exhibits excellent stability with negligible decay after 3000 cycles. Our work suggests a facile strategy that could be adopted to realize high-performance ECPs via molecular design tuning.     

Synthesis,dielectric, and microwave absorption properties of flake carbonyl iron particles coated with nanostructure polymer

Flake carbonyl iron particles (FCIPs) coated with nanostructure polymer (meth‐acrylic acid‐polystyrene, MAA‐PS) were synthesized by dispersion polymerization using poly (vinylpyrrolidone) as stabilizer and 2, 2‐azobis (isobutyronirile) as a catalytic agent. Field emission scanning electron microscope equipped with energy dispersive x‐ray spectroscopy and high‐resolution transmission electron microscope was used to observe its morphology of FCIPs‐MAA‐PS, and thermo‐gravimetric analyses were employed to characterize its mass loss of polymer surface modification. Electromagnetic properties of FCIPs before and after coating were investigated by Agilent 8720ET vector network analyzer within 0.5–18 GHz. After coated with nanostructure polymer, the real part of permittivity for FCIPs/wax composite was decreased while its permeability remained nearly unchanged. Dielectric behaviors were discussed by the Cole–Cole dispersion formula. After surface modification with nanostructure polymer, reflection loss of FCIPs‐MAA‐PS/wax composite presented a wide absorption band and showed the minimum value of reflection loss reaching ?39.4 dB when the thickness was 2.50 mm. Copyright © 2013 John Wiley & Sons, Ltd.     

高温超导混频器噪声系数测量

基于小型脉冲管制冷机,建立了以Josephson结为混频器的高温超导混频系统,并以Y-因子测量方法为基础,建立了与之配套的噪声系数测量系统。测量出以Josephson结为混频器的超导混频系统的噪声系数。在最好的情况下,测量的噪声系数值为5.50dB。