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A hexagonal honeycomb magnetic tunneling junction array with 72 nm pitch and 30 nm MgO critical dimension was successfully fabricated on a 1× nm dynamic random access memory platform by using a mature dynamic random access memory patterning solution and ion beam etch. To our knowledge, both pitch size and critical dimension size are the world's smallest ones for industrial magnetic tunneling junction arrays. To obtain such a high density and small sized magnetic tunneling junction array, a cross self-aligned double patterning technique, a triple layer hard mask scheme, and an optimized ion beam etch condition were adopted. During the optimization of the ion beam etch process, the dependence of a magnetic tunneling junction pillar profile on ion beam etch parameters for a high density hexagonal magnetic tunneling junction array has also been systematically studied. The depth of oxide recess and the magnetic tunneling junction sidewall angle increased with the ion beam etch amount, while magnetic tunneling junction critical dimension and hard mask remainder thickness decreased with increasing ion beam etch amount. [ABSTRACT FROM AUTHOR]

Since the thermal conduction equation has form invariance under coordinate transformation, one can design thermal metamaterials with novel functions by tailoring materials' thermal conductivities. In this work, we establish a different transformation theory, and propose a layered device with anisotropic thermal conductivities. The device is able to convert heat flux from parallel patterns into non-parallel patterns and vice versa. In the mean time, the heat flux pattern outside the device keeps undisturbed as if this device is absent. We perform finite-element simulations to confirm the converting behavior. This work paves a different way to manipulate the flow of heat at will. [ABSTRACT FROM AUTHOR]