Thermomechanical Nanomolding of Topological Materials

Topological intermetallic nanomaterials have novel symmetry-protected electronic states that are advantageous for applications such as catalysis¹, electronics², and quantum computing³. Fabrication of intermetallic nanomaterials is hindered by the lack of high throughput synthesis methods that allow for tight control of phase, morphology, and stoichiometry. Here, we present the use of thermomechanical nanomolding (TMNM) to fabricate nanowires of topological intermetallic materials. Developed by Jan Schroers’ group at Yale University, TMNM is a scalable fabrication process where a bulk feedstock is pressed through a mold with nanosized pores at elevated temperatures and pressures. Starting with a polycrystalline feedstock, TMNM forms defect-free, single crystalline nanowires with consistent growth orientation and composition.⁴ TMNM is materials agnostic and has been successfully used to create nanowires of several different topological materials.⁵ Furthermore, high pressures and temperatures used in the molding process can be exploited to study phase stability with the possibility of producing metastable phases through nanoscale confinement effects.<br/><br/>We used TMNM to fabricate nanowires of several different topological intermetallic materials. Due to the presence of symmetry-protected surface states, these topological materials have enhanced electronic properties that make them attractive candidates for next-generation interconnect materials. High-resolution S/TEM analysis reveals formation of high-quality, single-crystalline nanowires with consistent composition. Surprisingly, we observe that high levels of vacancies can be tolerated in these single-crystalline molded nanowires without forming any extended defects, such as nanoscale voids or phase separation. The molded nanowires show promising electrical properties where their resistivity values do not increase with decreasing dimensions of the nanowires, in contrast to the increasing resistivity of Cu interconnects at the nanoscale. Thus, we present TMNM as a high throughput fabrication method to form nanowires of topological intermetallic materials with controlled structure and electrical properties with promising applications in energy-efficient computing technologies.<br/><br/>References<br/>1. D. Wang, Q. Peng, Y. Li, Nano Res. <b>3</b>, 574-580 (2010).<br/>2. H.J. Han, D. Hynek, Z. Wu, L. Wang, P. Liu, J. V. Pondick, S. Yazdani, J.M. Woods, M. Yarali, Y. Xie, H. Wang, and J.J. Cha, APL Mater. <b>8</b>, 011103 (2020).<br/>3. S.M. Frolov, M.J. Manfra, and J.D. Sau, Nat. Phys. 2020 167 <b>16</b>, 718 (2020).<br/>4. N. Liu, Y. Xie, G. Liu, S. Sohn, A. Raj, G. Han, B. Wu, J.J. Cha, Z. Liu, and J. Schroers, Phys. Rev. Lett. <b>124</b>, 036102 (2020).<br/>5. Z. Liu, N. Liu, and J. Schroers, Prog. Mater. Sci. <b>125</b>, 100891 (2022).