Domain fracture and recovery process of metal phthalocyanine monolayers via NO2 and H2O.

CuPc ultrathin films (5 monolayers) are employed to detect NO₂ in chemFETs [organic thin film transistors (OTFTs)]; while the NO₂ causes OTFT degradation, H₂O restores OTFT performance. To develop an atomic understanding of this H₂O induced performance recovery, NO₂/CuPc/ Au(111) was exposed to H₂O, then observed using ultrahigh vacuum scanning tunneling microscopy. After dosing NO₂ (10 ppm for 5min) onto CuPc monolayers under ambient conditions, domain fracture is induced in CuPc monolayers, and CuPc aggregates are formed near new grain boundaries, consistent with dissociative O adsorption between CuPc molecules and Au(111). Conversely, after exposing H₂O onto a fractured CuPc monolayer for 30 min, fractured domains merge, then large area domains are generated. As the duration of H₂O exposure increases to 4 h, second layer growth of CuPc molecules is observed on the CuPc monolayers consistent with H₂O breakdown of CuPc aggregates which have formed at the domain boundaries. The results are consistent with H₂O driving the removal of atomic O between CuPc molecules and Au(111) consistent with previous sensing results. [ABSTRACT FROM AUTHOR]