Reactive Pulsed Laser Deposition of Epitaxial Bi ₂ O ₂ Se for Field‐Effect Transistor Application

A robust and CMOS‐compatible approach is introduced for the synthesis of high‐quality Bi 2 O 2 Se thin films using reactive pulsed laser deposition (RPLD). The process leverages an oxygen‐assisted transformation of Bi 2 Se 3 to enable the direct formation of Bi 2 O 2 Se with a strong out‐of‐plane (00 l ) orientation on amorphous SiO 2 ( a ‐SiO 2 ), c‐cut sapphire (c‐Al 2 O 3 ), and lattice‐matched SrTiO 3 (STO) substrates. Systematic optimization of oxygen background pressure, substrate temperature, and laser fluence reveals critical phase boundaries governing the transformation and allows suppression of vertically extended features such as (103)‐oriented Bi 2 O 2 Se and over‐oxidized (231)‐oriented vertical Bi 2 SeO 5 . Comprehensive structural and spectroscopic analyses, including Raman spectroscopy, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM), confirm the formation of phase‐pure, atomically smooth Bi 2 O 2 Se layers. Conductive AFM (C‐AFM) measurements establish a correlation between local film morphology and electronic transport, showing enhanced conductivity in misoriented Bi 2 O 2 Se domains and insulating behavior in Bi 2 SeO 5 regions. Preliminary field‐effect transistors (FETs) fabricated using RPLD‐grown Bi 2 O 2 Se as the semiconductor channel material on (100) STO exhibit a moderate on/off ratio, efficient gate control, and current driving capability. These results highlight RPLD as a powerful technique for integrating layered oxychalcogenides into next‐generation electronic and optoelectronic platforms.