Stoichiometry‐Controlled Growth of 2D PtSe _x Films for n‐PtSe _1.7 /p‐PtSe Yunjin Lee, Jin Hyeok Lee, Dongki Shin, Youngjo Choi, Jiyoung Kim, Hoyoung Suh, Young Woo Jeong, Kwang Seob Jeong, Woong Kim

ABSTRACT

2D heterostructures have promising potential for applications in mid‐infrared (MWIR) photodetection but often suffer from transfer‐induced interfacial defects and limited micrometer‐scale active areas. In this study, PtSe _x thin films are synthesized via a scalable thermally assisted conversion (TAC) method that enables precise stoichiometry control and carrier‐type conversion from Se‐deficient n ‐type to Se‐rich p ‐type phases. Structural and spectroscopic analyses confirm layered structures and defect‐induced mid‐gap states that improve infrared absorption and facilitate bandgap engineering. Functional 2D/2D photodetectors are fabricated via a two‐step TAC approach that leads to vertically stacked n‐PtSe _1.7 /p‐PtSe ₂ junctions. The top n ‐type layer is rapidly synthesized without disturbing the underlying p ‐type film because n ‐type PtSe _1.7 forms within tens of seconds, whereas the formation of p ‐type PtSe ₂ requires several minutes. This kinetic selectivity preserves pristine interfaces, yielding reproducible rectification and robust MWIR photoresponse with a specific detectivity of 3.8 × 10 ⁹  Jones across centimeter‐scale active areas. This study establishes PtSe _x as a scalable material platform, with the transfer‐free growth approach and uniform film quality highlighting its strong potential for wafer‐scale integration of layered heterojunction devices.