Intrinsic physical properties of flexible van der Waals semiconductor InSe

TL;DR

This paper reports the successful synthesis of high-quality, intrinsic InSe single crystals using the traveling solvent floating zone method, enabling more accurate studies of its fundamental physical properties.

Contribution

It introduces a novel synthesis approach for phase-pure InSe crystals, overcoming thermodynamic constraints of traditional methods.

Findings

TSFZ method produces centimeter-size, high-quality InSe crystals.

Transport measurements show properties close to intrinsic limits.

Establishes InSe as a benchmark material for future research.

Abstract

InSe is a van der Waals semiconductor in which mechanical flexibility, high electronic mobility, and non-trivial electronic structures converge, making it an attractive platform for both intriguing fundamental studies and promising device developments. However, the nucleation and growth of phase-pure, intrinsic InSe crystals require stringent thermodynamical conditions, and have therefore remained elusive. Since InSe melts incongruently, the widely used synthesis methods based on cooling of a 1:1 In-Se mixture will produce either aggregates of multiphase crystallites or uncontrolled In-rich, heavily electron-doped InSe. This fundamental thermodynamic constraint provides a compelling explanation for the large discrepancies observed in the reported physical properties of InSe. We overcome these limitations by utilizing the traveling solvent floating zone (TSFZ) method to produce high quality, centimeter-size InSe single crystals. Electrical, thermal, and thermoelectric transport measurements demonstrate that TSFZ-InSe single crystals closely approach the intrinsic limit, establishing it as a benchmark material for the future studies of this important material.