Stoichiometry‐Controlled Growth of 2D PtSe x Films for n‐PtSe 1.7 /p‐PtSe 2 Mid‐Wave Infrared Photodetectors Toward Scalable Integration

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.