Plasma enhanced-CVD of undoped and fluorine-doped Co3O4 nanosystems for novel gas sensors

Co3O4-based nanosystems were prepared on polycrystalline Al2O3 by plasma enhanced-chemical vapor deposition (PE-CVD), at temperatures ranging between 200 and 400 °C. The use of two different precursors, Co(dpm)2 (dpm = 2,2,6,6-tetramethyl-3,5-heptanedionate) and Co(hfa)2·TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) enabled the synthesis of undoped and fluorine-doped Co3O4 specimens, respectively. A thorough characterization of their properties was performed by glancing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), field emission-scanning electron microscopy (FE-SEM), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). For the first time, the gas sensing properties of such PE-CVD nanosystems were investigated in the detection of ethanol and acetone. The results show an appreciable response improvement upon doping and functional performances directly dependent on the fluorine content in the Co3O4 system.