Helium ion beam milling to create a nano-structured domain wall magnetoresistance spin valve
Helium ion beam milling to create a nano-structured domain wall magnetoresistance spin valve
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DOI：
10.1088/0957-4484/23/39/395302
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发表时间：
2012-10
期刊：
影响因子：
3.5
通讯作者：
Yudong Wang;S. Boden;D. Bagnall;H. Rutt.;C. D. de Groot
中科院分区：
文献类型：
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作者：
Yudong Wang;S. Boden;D. Bagnall;H. Rutt.;C. D. de Groot
我们利用电子束光刻和氦离子束研磨的新组合，制作并测量了禁带宽度小于20 nm的单畴壁磁电阻器件。采用电子束曝光法和剥离技术制作了自旋阀的测量线和外形。关键的电桥结构是使用氦离子束研磨创建的，能够形成比单独使用电子束技术可能的更薄的间隙(因此也就是更窄的磁区壁)。用四点探针电阻测量和扫描电子显微镜对球磨结构进行了表征，并优化了He离子剂量。结果表明，该器件作为自旋阀运行成功，在外加磁场的作用下，其电阻变化为0.2%。从电阻测量中提取的氦离子束研磨效率为0.044个原子/离子，大约是理论值的一半。这种技术将器件的间隙限制在最大20 nm以内，因为注入的离子会引起亚表面膨胀，这可能会导致器件的灾难性故障。氦离子显微镜研磨技术的精细图案化能力表明，5 nm以下的收缩宽度是可能的。
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.