  Platinum diselenide (PtSe${_2}$) is a two-dimensional (2D) material with
outstanding electronic and piezoresistive properties. The material can be grown
at low temperatures in a scalable manner which makes it extremely appealing for
many potential electronics, photonics, and sensing applications. Here, we
investigate the nanocrystalline structure of different PtSe${_2}$ thin films
grown by thermally assisted conversion (TAC) and correlate them with their
electronic and piezoresistive properties. We use scanning transmission electron
microscopy for structural analysis, X-ray photoelectron spectroscopy (XPS) for
chemical analysis, and Raman spectroscopy for phase identification. Electronic
devices are fabricated using transferred PtSe${_2}$ films for electrical
characterization and piezoresistive gauge factor measurements. The variations
of crystallite size and their orientations are found to have a strong
correlation with the electronic and piezoresistive properties of the films,
especially the sheet resistivity and the effective charge carrier mobility. Our
findings may pave the way for tuning and optimizing the properties of TAC-grown
PtSe${_2}$ towards numerous applications.
