Stacking polymorphism in PtSe$_2$ drastically affects its electromechanical properties

TL;DR

This paper investigates how different stacking phases in PtSe$_2$ influence its electromechanical properties, revealing that stacking polymorphism significantly affects sensor performance and can be controlled during synthesis.

Contribution

It demonstrates the presence of various stacking phases in PtSe$_2$ thin films at high temperatures and assesses their impact on electromechanical properties.

Findings

Stacking phases other than AA are thermodynamically accessible at high temperatures.

Stacking polymorphism significantly alters gauge factors in PtSe$_2$.

Methods to characterize stacking phases are discussed.

Abstract

PtSe$_2$ is one of the most promising materials for the next generation of piezoresistive sensors. However, the large-scale synthesis of homogeneous thin films with reproducible electromechanical properties is challenging due to polycrystallinity. We show that stacking phases other than the AA-stacking in the 1T phase become thermodynamically available at elevated temperatures. We show that these can make up a significant fraction in a polycrystalline thin film and discuss methods to characterize these stacking phases. Lastly, we estimate their gauge factors, which vary strongly and significantly impact the performance of a nanoelectromechanical device.