Search for: All records

Directed self-assembly (DSA) of block copolymers (BCPs) has long been included in the semiconductor roadmap as a lithographic pathway to enable continued device scaling. Tremendous progress has been made in generating two-dimensional (2D) BCP patterns with device-relevant features and low defect density and in transferring these patterns to functional materials. Extension of pattern generation into 3D could markedly enhance the utility of BCPs in nanoscale manufacturing, but methods to template and synthesize well-ordered, nontrivial 3D structures are less well developed. Here, we demonstrate a hierarchical DSA method to generate cross-point structures with connected in-plane and out-of-plane segments and controlled orientation angle between the horizontal layers. Various highly ordered, 3D interconnected networks, including ladder and cross-point structures, are produced by combinations of surface modification, BCP periodicity, and topographic templates, expanding the capabilities of BCP-derived nanofabrication. 

Abstract Exchange bias (EB), manifested as a hysteresis‐loop offset after field‐cooling, is demonstrated in perovskite‐structured ferromagnet/antiferromagnet (La_0.67Sr_0.33MnO₃/YFeO₃)_nheterostructures grown on (100) SrTiO₃substrates. Bilayer samples show an EB of 306 Oe at 50 K, whereas multilayers with five layers exhibit an exchange bias of up to 424 Oe at 50 K. A spin valve consisting of La_0.67Sr_0.33MnO₃/SrTiO₃/La_0.67Sr_0.33MnO₃/YFeO₃shows stable remanent configurations resulting from pinning of the upper La_0.67Sr_0.33MnO₃layer by the YFeO₃. In contrast, EB is not observed on (111)‐oriented SrTiO₃substrates due to interface roughening. These results demonstrate YFeO₃as an alternative orthoferrite antiferromagnet compared to BiFeO₃and LaFeO₃for incorporation into exchange‐biased heterostructures.