A Polymeric Planarization Strategy for Versatile Multi-terminal Electrical Transport Studies on Small, Bulk Quantum Materials

TL;DR

This paper introduces a polymeric planarization fabrication method enabling reliable multi-terminal electrical contact formation on small, sensitive quantum materials, facilitating advanced transport measurements and heterostructure integration.

Contribution

A novel polymer-based planarization technique that overcomes size and thickness limitations for electrical contact fabrication on small quantum materials.

Findings

Enabled transport studies on small BaTiS3 crystals

Facilitated in-plane anisotropy and Hall measurements

Supported integration of diverse quantum materials

Abstract

We report a device fabrication strategy of making multi-terminal electrical contacts on small (< 1 mm) bulk quantum materials using lithography-based techniques for electrical transport studies. The crystals are embedded in a polymeric medium to planarize the top surface, and then standard lithography and microfabrication techniques are directly applied to form electrodes with various geometries. This approach overcomes the limitations of crystal thickness and lateral dimensions on establishing electrical contacts. We use low stress polymers to minimize the extrinsic thermal strain effect at low temperatures, which allow reliable transport measurements on quantum materials that are sensitive to strain. The crystal surface planarization method has enabled electronic transport studies such as in-plane anisotropy, Hall measurements on small, bulk BaTiS3 (BTS) crystals, and provides unique opportunities for two-dimensional (2D) heterogeneous integration on three-dimensional (3D) / quasi-one-dimensional (quasi-1D) bulk materials. Our strategy is general for many small, non-exfoliable crystals of newly synthesized quantum materials and paves the way for performing versatile transport studies on those novel materials.