Fabrication of voltage gated spin Hall nano-oscillators
arXiv:2111.06957 · doi:10.1039/D1NR07505E
Abstract
We demonstrate an optimized fabrication process for electric field (voltage gate) controlled nano-constriction spin Hall nano-oscillators (SHNOs), achieving feature sizes of <30 nm with easy to handle ma-N 2401 e-beam lithography negative tone resist. For the nanoscopic voltage gates, we utilize a two-step tilted ion beam etching approach and through-hole encapsulation using 30 nm HfO<sub>x</sub>. The optimized tilted etching process reduces sidewalls by 75% compared to no tilting. Moreover, the HfO<sub>x</sub> encapsulation avoids any sidewall shunting and improves gate breakdown. Our experimental results on W/CoFeB/MgO/SiO<sub>2</sub> SHNOs show significant frequency tunability (6 MHz/V) even for moderate perpendicular magnetic anisotropy. Circular patterns with diameter of 45 nm are achieved with an aspect ratio better than 0.85 for 80% of the population. The optimized fabrication process allows incorporating a large number of individual gates to interface to SHNO arrays for unconventional computing and densely packed spintronic neural networks.
8 Pages, 5 Figures
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