INL is capable to fabricate nanopillars out of MTJ stacks with diameters below 100 nm. We succeeded with the typical stack with free layer on top of the stack as well as reversed stacks. The later have the benefit of a free layer that is in direct contact with the bottom contact material. These two approaches were applied to fabricate devices used for research on MTJ-based spin transfer torque nano-oscillators (STNOs) and Spin Hall nano-oscillators (SHNOs) described in the following.
Two MTJ nanopillars in an intermediate fabrication step defined by e-beam lithography. Both have a diameter far below 100 nm and show TMR signals of up to 120%.
Flow diagram of the planarization process for achieving high quality electrical contacts to MTJ nanopillars.
Cross section of an MTJ nanopillar. This image was created by cutting the sample by a focused ion beam in a thin lamella and imaging the electron transmission through the sample.
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