The development of the 3D magnetic sensor using the nano-SQUID

我们开发了一种可以应用于三维磁传感器的Nb基纳米SQUID的制备工艺。利用Nb、Nb/W、Nb/Au薄膜制备了SQUID，并用常规光刻和聚焦离子束(FIB)工艺进行了图案化。结果表明，双层膜能有效地减小FIB过程中的自热效应，避免由于Ga离子的扩散而引起的退化。我们成功地制备了具有非滞后I-V特性的双层纳米SQUID，在4.2K时，其IC可达30 mA。通过改变FIB模式，可以很容易地调整IC值。因此，目前的制备工艺可以灵活地优化SQUID设计，以适应各种测量环境，如高磁场(~1T)和低温(0.1K)。

We develop a fabrication process of Nb based nano-SQUIDs that can be applied for three dimensional magnetic sensor. The SQUIDs were fabricated using Nb, Nb/W, Nb/Au films and patterned by a conventional lithography and a focused ion beam (FIB) process. The bilayer films were found to be effective to reduce the effects of the self-heating and to avoid the degradation due to the Ga ion diffusion during the FIB process. We succeeded in fabricating bilayer nano-SQUIDs having nonhysteretic I-V characteristics with Ic down to 30mA at 4.2K. Ic values could be easily tuned by changing the FIB pattern. Therefore, the present fabrication process has the flexibility to optimize the SQUID design for various measurement environments, such as for high magnetic field (～1T) and for low temperature (0.1K).