Nanostructured W–Cr Janus Heterojunctions Prepared by Glancing Angle Deposition for Gas Sensing

In this paper, a nanostructured W–Cr Janus thin film was synthesized using the GLancing Angle Deposition cosputtering technique. The film was elaborated using pure W and Cr targets positioned at equal and fixed deposition angles of 80°, resulting in vertically aligned bicomponent nanocolumns. The morphological and crystallographic properties of the W–Cr Janus thin film were studied before and after annealing treatment in air, as high as 500 °C. Investigations revealed that annealing induces the formation of a fully oxidized surface envelope composed of p-type Cr 2 O 3 and n-type WO 3, which nonuniformly covers the Janus nanocolumns. The chemical gas sensor based on the annealed W–Cr Janus thin film demonstrated promising sensing performances, achieving detection limits of approximately 37 ± 5, 26 ± 5, and 36 ± 5 ppb for benzene, formaldehyde, and propanol, respectively. Beyond representing a technical advancement in the field of cosputtered thin films, this study underscores the potential of this bicomponent heterojunction structure for the detection of trace-level air pollutants.