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Diwen wuli xuebao

Al/Al2O3/Al隧道结相位扩散的现象

W.‐R. Lin, 许伟伟, 翟计全, 李晓虎, 孙国柱, 吴培亨

Published Jan 1, 2015• 0 citations
OpenAlex

Abstract

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.

Related papers

THE PHENOMENON OF PHASE DIFFUSIONIN Al/Al_2O_3/Al TUNNEL JUNCTIONS

Wang Li

Josephson junction is the key element of the superconducting quantum bits.DC superconducting quantum interference device(DC-SQUID)plays a important role in the measurement of superconducting flux quantum bit because of its high sensitivity in magnetic field probe.By evaporating aluminum from slanted angles and the method of static oxidization,we fabricated the DC-SQUID sample composed by two parallel tunnel junctions Al/Al2O3/Al.Placing the sample in different temperature between 20 mK and 1000 mK,we had the measurement of switching current distribution(SCD).The transition from macroscopic quantum tunneling mechanism(MQT)to thermal activation(TA)is clearly observed in 50 mK.When the temperature is higher than 80 mK,the phase diffusion phenomenon(PD)is observed.It is of great importance for the research of phase dynamics of tunnel junction.

Diwen wuli xuebao•Jan 1, 2015•0 citations

超导磁通量子比特的制备及Al/AlOx/Al隧道结特性参数

W.‐R. Lin, 许伟伟, 翟计全 +3 more

超导量子比特作为利用约瑟夫森结实现量子位的方案之一,具有易集成、易与外界耦合等优点.用双层光刻胶通过深紫外光曝光制备悬空掩膜结构,Al作为超导材料,采用电子束斜蒸发及静态氧化的方法制备了超导磁通量子比特样品.通过对Al薄膜厚度与平整度关系分析,选取60 nm作为隧道结底层Al厚度,增加蒸发源到样品衬底间的距离,提高了Al薄膜平整度,降低了隧道结漏电流.通过透射电子显微镜分析,观测到Al隧道结三层结构,并得到了势垒层厚度和氧分压的关系.

科学通报•Jan 1, 2014•0 citations

超导量子比特中铝超导隧道结的性能

俊杰 常, 国柱 孙, 争鸣 吉 +5 more

超导隧道结约瑟夫森结是超导量子比特的基本元件. 用双层光刻胶构成悬空掩模,用电子束斜蒸发的方法制备Al/Al2O3/Al 隧道结, 用一定的氧气气压氧化铝膜作为势垒层.势垒层质量直接影响铝超导隧道结的各项电学参数. 深入研究了铝超导隧道结的超导临界电流密度Jc和面积归一化电阻Rc(正常态电阻RN与结面积的乘积)与势垒层生长条件的关系,通过改变势垒层生长的氧分压与氧化时间来控制铝超导隧道结的Jc 和Rc, 以使此工艺所制备的铝隧道结漏电流小, 结参数易于控制, 满足制备超导量子比特的要求.

Chinese Science Bulletin (Chinese Version)•Nov 1, 2011•1 citation

Processing of DC SQUIDs for radiofrequency amplification

R. Chicault, M. C. Cyrille, Y. Berthier +4 more

The goal of this studies is to use dc Squids as low noise radiofrequency amplifier (Tn ≈1K) in the frequency range 1-150 Mhz and to integrate them in NMR probe. DC Squids have been built using planar technology and with two types of superconducting materials : low Tc(Nb) and High Tc(YBa2Cu3O7). Contrary to the traditional set up used in magnetometry (flux locked loop) the dc Squid is here fluxed biased near Φz=(2n+1)Φo/4 and no flux locked loop is connected. Small variations of flux (Φs<<Φo) introduced from signal source via the input coil are amplified following the transfer characteristic VΦ=dV/dΦ. The low Tc devices are set up to now the best, concerning the reproducibility and the qualities of the Josephson Junctions obtained with a three layer process Nb/Al-Al2O3/Nb. Such junctions have been realized following the so called SNOP process, without anodization. The main characteristic obtained at 4.2K are RJ/RN=10, 2Δ≈2.8 meV and a Josephson current density J≈103 A/cm2. The high Tc devices have been built with bi-epitaxial YBa2Cu3O7 junctions and with a 30x30µm2 area loop. I(V) and V(Φ) characteristics curves obtained are promizing for applications as RF detection in the temperature range : 4-77K. Modelization studies are currently in progress for the optimization of those devices (low Tc and high Tc) as RF amplifiers (minimization of parasitic capacitance between the input coil and the Squid loop) in order to increase their upper frequency limit.\n* This work is partially supported by Ultimatech (CNRS), by the "région Rhône-Alpes" and E.E.C. "HTSC-GBJ" programs n°7100.

Journal de Physique IV (Proceedings)•Jun 1, 1994•2 citations

Multichannel DC SQUID System

Hisao Furukawa, K. Shirae

A new essential multichannel dc SQUID system has been devised. The system consists of two stages of dc SQUIDs; in the first stage, a number of dc SQUIDs equivalent to the input number detect the input signals, and the sum of the first-stage output modulates the carrier of the second-stage dc SQUID and is sent by the carrier to a room temperature amplifier, where the mixed input signals are separated into the original signals. To verify the system operation, a three channel dc SQUID system has been developed and good results have been obtained.

Japanese Journal of Applied Physics•Mar 1, 1989•8 citations

利用倾斜角度蒸发法制备Al/Al_2O_3/Al超导隧道结

陆殷华, 许伟伟, 沈丹丹 +4 more

利用电子束曝光法对双层光刻胶进行曝光来制备悬空掩模结构,在此基础上利用电子束蒸发系统采用倾斜角度蒸发法制备铝超导薄膜,采用热氧化法在底层铝膜表面形成氧化铝作为势垒层,制备出铝SIS超导隧道结,并在360mK的情况下对铝结进行了Ⅰ～Ⅴ特性的初步测量.铝隧道结的成功制备为下一步构建超导量子比特器件,研究其量子特性奠定了良好的基础.

Diwen wuli xuebao•Jan 1, 2010•0 citations
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.
Josephson junction is the key element of the superconducting quantum bits.DC superconducting quantum interference device(DC-SQUID)plays a important role in the measurement of superconducting flux quantum bit because of its high sensitivity in magnetic field probe.By evaporating aluminum from slanted angles and the method of static oxidization,we fabricated the DC-SQUID sample composed by two parallel tunnel junctions Al/Al2O3/Al.Placing the sample in different temperature between 20 mK and 1000 mK,we had the measurement of switching current distribution(SCD).The transition from macroscopic quantum tunneling mechanism(MQT)to thermal activation(TA)is clearly observed in 50 mK.When the temperature is higher than 80 mK,the phase diffusion phenomenon(PD)is observed.It is of great importance for the research of phase dynamics of tunnel junction.
超导量子比特作为利用约瑟夫森结实现量子位的方案之一,具有易集成、易与外界耦合等优点.用双层光刻胶通过深紫外光曝光制备悬空掩膜结构,Al作为超导材料,采用电子束斜蒸发及静态氧化的方法制备了超导磁通量子比特样品.通过对Al薄膜厚度与平整度关系分析,选取60 nm作为隧道结底层Al厚度,增加蒸发源到样品衬底间的距离,提高了Al薄膜平整度,降低了隧道结漏电流.通过透射电子显微镜分析,观测到Al隧道结三层结构,并得到了势垒层厚度和氧分压的关系.
超导隧道结约瑟夫森结是超导量子比特的基本元件. 用双层光刻胶构成悬空掩模,用电子束斜蒸发的方法制备Al/Al2O3/Al 隧道结, 用一定的氧气气压氧化铝膜作为势垒层.势垒层质量直接影响铝超导隧道结的各项电学参数. 深入研究了铝超导隧道结的超导临界电流密度Jc和面积归一化电阻Rc(正常态电阻RN与结面积的乘积)与势垒层生长条件的关系,通过改变势垒层生长的氧分压与氧化时间来控制铝超导隧道结的Jc 和Rc, 以使此工艺所制备的铝隧道结漏电流小, 结参数易于控制, 满足制备超导量子比特的要求.
The goal of this studies is to use dc Squids as low noise radiofrequency amplifier (Tn ≈1K) in the frequency range 1-150 Mhz and to integrate them in NMR probe. DC Squids have been built using planar technology and with two types of superconducting materials : low Tc(Nb) and High Tc(YBa2Cu3O7). Contrary to the traditional set up used in magnetometry (flux locked loop) the dc Squid is here fluxed biased near Φz=(2n+1)Φo/4 and no flux locked loop is connected. Small variations of flux (Φs<<Φo) introduced from signal source via the input coil are amplified following the transfer characteristic VΦ=dV/dΦ. The low Tc devices are set up to now the best, concerning the reproducibility and the qualities of the Josephson Junctions obtained with a three layer process Nb/Al-Al2O3/Nb. Such junctions have been realized following the so called SNOP process, without anodization. The main characteristic obtained at 4.2K are RJ/RN=10, 2Δ≈2.8 meV and a Josephson current density J≈103 A/cm2. The high Tc devices have been built with bi-epitaxial YBa2Cu3O7 junctions and with a 30x30µm2 area loop. I(V) and V(Φ) characteristics curves obtained are promizing for applications as RF detection in the temperature range : 4-77K. Modelization studies are currently in progress for the optimization of those devices (low Tc and high Tc) as RF amplifiers (minimization of parasitic capacitance between the input coil and the Squid loop) in order to increase their upper frequency limit.\n* This work is partially supported by Ultimatech (CNRS), by the "région Rhône-Alpes" and E.E.C. "HTSC-GBJ" programs n°7100.
A new essential multichannel dc SQUID system has been devised. The system consists of two stages of dc SQUIDs; in the first stage, a number of dc SQUIDs equivalent to the input number detect the input signals, and the sum of the first-stage output modulates the carrier of the second-stage dc SQUID and is sent by the carrier to a room temperature amplifier, where the mixed input signals are separated into the original signals. To verify the system operation, a three channel dc SQUID system has been developed and good results have been obtained.