An integrated superconductive magnetic nanosensor for high-sensitivity nanoscale applications
An integrated superconductive magnetic nanosensor for high-sensitivity nanoscale applications
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DOI：
10.1088/0957-4484/19/27/275501
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发表时间：
2008-07
期刊：
影响因子：
3.5
通讯作者：
C. Granata;E. Esposito;A. Vettoliere;L. Petti;M. Russo
中科院分区：
文献类型：
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作者：
C. Granata;E. Esposito;A. Vettoliere;L. Petti;M. Russo
提出了一种基于铌直流超导量子干涉器件（SQUID）的集成纳米磁传感器。该传感器由Nb（30 nm）/Al（30 nm）双层膜组成，通过电子束光刻（EBL）构图，剥离和反应离子刻蚀（RIE）工艺成型，具有200 nm的孔和两个80 nm × 100 nm的Josephson-Dayem纳米桥。铌线圈的存在，集成在芯片上，并紧密耦合到SQUID，使我们能够轻松地激励传感器，以获得电压-磁通特性，并在其最佳点的SQUID的磁通偏置。测量在液氦温度下进行。从电压-通量特性直接测得75 µV的电压摆幅和高达1 mV/Φ0的最大电压-通量传递系数（响应度）。噪声测量在开环模式下进行，偏置SQUID与直流磁通量在其最大响应点，并使用直接耦合的低噪声读出电子。实现了低至2.5 μΦ0 Hz−1/2的白色磁通噪声谱密度，对应于以100自旋Hz−1/2的玻尔磁子为单位的磁化或自旋灵敏度。这种纳米传感器的可能应用可以设想在纳米粒子和原子和分子的小簇的磁检测，在纳米物体磁化的测量，并在量子计算。
An integrated magnetic nanosensor based on a niobium dc SQUID (superconducting quantum interference device) for nanoscale applications is presented. The sensor, having a washer shape with a hole of 200 nm and two Josephson–Dayem nanobridges of 80 nm × 100 nm, consists of a Nb(30 nm)/Al(30 nm) bilayer patterned by electron beam lithography (EBL) and shaped by lift-off and reactive ion etch (RIE) processes. The presence of the niobium coils, integrated on-chip and tightly coupled to the SQUID, allows us to easily excite the sensor in order to get the voltage–flux characteristics and to flux bias the SQUID at its optimal point. The measurements were performed at liquid helium temperature. A voltage swing of 75 µV and a maximum voltage–flux transfer coefficient (responsivity) as high as 1 mV/Φ0 were directly measured from the voltage–flux characteristic. The noise measurements were performed in open loop mode, biasing the SQUID with a dc magnetic flux at its maximum responsivity point and using direct-coupled low-noise readout electronics. A white magnetic flux noise spectral density as low as 2.5 μΦ0 Hz−1/2 was achieved, corresponding to a magnetization or spin sensitivity in units of the Bohr magneton of 100 spin Hz−1/2. Possible applications of this nanosensor can be envisaged in magnetic detection of nanoparticles and small clusters of atoms and molecules, in the measurement of nanoobject magnetization, and in quantum computing.