Frankvan der Merwe Growth of Millimeter‐Scale PtSe ₂ Single‐Crystal Films for Bidirectional Photoresponse

Abstract Platinum diselenide (PtSe 2 ) has attracted great interesting in novel electronic and optoelectronic devices due to its unique band structure and carrier transport characteristics. Moreover, the preferred hole conductive behavior and high ambient stability makes it as the promising candidate in 2D p‐type semiconductor family. However, the strong interlayer van der Waals forces make PtSe 2 prefer vertical‐direction growing with thick‐island morphography obeying Volmer‐Weber growth mechanism. Herein, a molten salt‐assisted and spatially confined chemical vapor deposition method was employed to grow PtSe 2 . It was found that under the assisting of salt‐activating and confining effects, the growth obeys Frank‐van der Merwe mechanism and the millimeter‐scale PtSe 2 single‐crystal films is successfully obtained which is as known the largest until now. Through fabricating the transistor, the PtSe 2 film exhibit typical bipolar electrical behavior. The PtSe 2 phototransistors display gate‐ and wavelength‐programmable bidirectional photoresponse, showing hole‐dominated negative photoconductivity under 520 nm illumination with a maximum responsivity of ‐143.7 mA W −1 . Furthermore, by studying the temperature‐dependent electrical transport and photoresponse, the band structure and photoelectrical effect is discussed revealing the intrinsic physical mechanisms of the bipolar behavior and negative photoconductivity effect in PtSe 2 . This work opens the synthesis of strongly coupled dichalcogenide single crystals film.