Approaching the Monolayer Limit of Carbon Layers by Pyrolysis of Polymer Films

ABSTRACT Research on monolayer materials remains at the forefront of materials research. Here, we present a systematic study of graphenic carbon layers focusing on their structural evolution and electrical properties as film thickness approaches the atomic limit. The ultrathin carbon films are obtained from the pyrolysis of photoresist films (PPF) directly on the target substrate, also allowing structuring by lithographic means. Thus, pre‐defined graphenic structures can be realized with controlled thickness, down to the sub‐nanometer scale as determined by atomic force microscopy. X‐ray photoelectron spectroscopy confirms the predominant sp 2 hybridization of our films, transmission electron microscopy reveals domains with hexagonal atomic structure, and Raman spectroscopy shows signatures of evolving nanocrystallinity with decreasing film thickness until dimensional confinement imposes a lower limit. We further demonstrate the functionality of the sub‐nanometric pyrolyzed polymer film as a chemiresistive NO 2 sensor. The films' scalability and patternability across multiple length scales, together with their chemical inertness and biocompatibility, make them promising candidates for future applications.