Extensive pore formation occurs during laser treatment. In the upper transducer layer, open, interconnected macropores are generated as indicated by the complete infiltration by epoxy resin (Figure ). That pore network ensures the excellent accessibility to the active N-sites of the sensor layer by the analyte and carrier gas. Only a sparse network of graphitized carbon remains, which is laterally interconnected and ensures a sufficient charge transport capability. The sensor layer exhibits a generally lower degree of porosity as expected from the reduced laser impact at larger depths. Only a minor volume fraction of enclosed meso-and macropores was observed (e.g., unfilled pores in Figure , D (left), Figure ). A quite narrow transition zone between the sensor and transducer layer is corroborated by the cross-sectional analyses (Figure ).