Stacking polymorphism in PtSe2 drastically affects its electromechanical properties

PtSe2 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 1T phase become thermodynamically available at elevated temperatures that are common during synthesis. We show that these phases can make up a significant fraction in a polycrystalline thin film and discuss methods to characterize them, including their Seebeck coefficients. Lastly, we estimate their gauge factors, which vary strongly and heavily impact the performance of a nanoelectromechanical device.