School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK.
Nanotechnology. 2012 Oct 5;23(39):395302. doi: 10.1088/0957-4484/23/39/395302. Epub 2012 Sep 12.
We have fabricated and measured single domain wall magnetoresistance devices with sub-20 nm gap widths using a novel combination of electron beam lithography and helium ion beam milling. The measurement wires and external profile of the spin valve are fabricated by electron beam lithography and lift-off. The critical bridge structure is created using helium ion beam milling, enabling the formation of a thinner gap (and so a narrower domain wall) than that which is possible with electron beam techniques alone. Four-point probe resistance measurements and scanning electron microscopy are used to characterize the milled structures and optimize the He ion dose. Successful operation of the device as a spin valve is demonstrated, with a 0.2% resistance change as the external magnetic field is cycled. The helium ion beam milling efficiency as extracted from electrical resistance measurements is 0.044 atoms/ion, about half the theoretical value. The gap in the device is limited to a maximum of 20 nm with this technique due to sub-surface swelling caused by injected ions which can induce catastrophic failure in the device. The fine patterning capabilities of the helium ion microscope milling technique indicate that sub-5 nm constriction widths could be possible.
我们使用电子束光刻和氦离子束铣削的新颖组合，制造并测量了具有小于 20nm 间隙宽度的单畴壁磁阻器件。测量线和自旋阀的外部轮廓通过电子束光刻和剥离工艺制造。关键的桥结构是通过氦离子束铣削创建的，这使得能够形成比仅使用电子束技术更薄的间隙（因此更窄的畴壁）。四点探针电阻测量和扫描电子显微镜用于表征铣削结构并优化氦离子剂量。成功地将器件用作自旋阀进行了演示，当外部磁场循环时，电阻变化为 0.2%。从电阻测量中提取的氦离子束铣削效率为 0.044 个原子/离子，约为理论值的一半。由于注入离子引起的亚表面肿胀，该技术将器件的间隙限制在最大 20nm 以内，这可能会导致器件灾难性失效。氦离子显微镜铣削技术的精细图案化能力表明，亚 5nm 的收缩宽度是可能的。
