Fig. 5: Device workflow and pitfalls.

a Overview of the workflow from thin film to device prototype. b Schematic illustrating the post-lithography state, where thin layers of photoresist residue remain after development. c Schematics comparing dry etching (left) and wet etching (center). Wet etching produces an undercut, whose extent varies among different material layers. Scanning Electron Microscope (SEM) images (right) show an example where the color contrast is due to an undercut around the device edge. d SEM images of a successful (left) and an unsuccessful (right) prototype fabricated under near identical conditions. The hypersensitivity of chalcogenide materials demands careful processing to avoid unwanted chemical reactions. e Schematic of the lift-off process comparing two resist configurations: a bilayer (left) and a single-layer (right). In the bilayer configuration, differing development rates create an overhang that causes the metal layer to break at the top, enabling a cleaner lift-off. By contrast, a continuous metal film in the single-layer approach can inadvertently lift off with the resist, risking unwanted metal removal.