NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications
NANO-SQUIDs based on niobium Dayem bridges for nanoscale applications
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基于铌 Dayem 桥的 NANO-SQUID，用于纳米级应用
DOI：
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发表时间：
2010
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通讯作者：
M. Russo
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作者：
C. Granata;A. Vettoliere;P. Walke;E. Esposito;C. Nappi;P. Silvestrini;B. Ruggiero;M. Russo
我们报告了基于铌dc-SQUID（超导量子干涉装置）的纳米级应用集成磁性纳米传感器的设计、制造和性能。纳米传感器基于插入边长为 200 nm 的方形环中的纳米铌收缩（Dayem 桥）。报告了电压磁通特性、磁通电压传输因子和噪声性能的测量结果。在小信号模式下，传感器显示出 1.5 μΦ0/Hz1/2 的磁通量噪声谱密度，对应于 60 spin/Hz1/2（以玻尔磁子为单位的自旋灵敏度）。还报告了这些设备的超电流衰减测量。此类测量为使用 SQUID 作为传感器工作在零电压状态的触发器的应用提供了有用的信息。实验数据显示，在液氦温度下，固有电流波动小于临界电流的0.2%，对应于几mΦ0的固有传感器磁通量分辨率。鉴于纳米 SQUID 在检测小自旋群体中的应用，作者计算了相对于单个自旋的自旋灵敏度和磁响应，作为其在 SQUID 孔内位置的函数。结果表明 SQUID 响应强烈依赖于自旋位置。
We report on the design, the fabrication and the performance of an integrated magnetic nano-sensor based on niobium dc-SQUID (Superconducting QUantum Interference Device) for nanoscale applications is presented. The nano-sensors are based on nanometric niobium constrictions (Dayem bridges) inserted in a square loop having a side length of 200 nm. Measurements of voltage-flux characteristic, flux to voltage transfer factor and noise performances are reported. In small signal mode, the sensors have shown a magnetic flux noise spectral density of 1.5 μΦ0/Hz1/2 corresponding to a spin sensitivity in unit of Bohr magneton of 60 spin/Hz1/2. Supercurrent decay measurements of these devices are also reported. Such measurements provide useful information for applications which employ the SQUID as a trigger where the sensor works on the zero voltage state. The experimental data, have shown an intrinsic current fluctuation less than 0.2% of the critical current at liquid helium temperature, corresponding to an intrinsic sensor magnetic flux resolution of a few mΦ0. In view of the nano-SQUID employments in the detection of small spin populations, the authors calculated the spin sensitivity and the magnetic response relative to the single spin, as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position.