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Magnetron discharge plasma was applied for the synthesis of CN x thin layers using methane and nitrogen gas precursors. The incorporation of nitrogen in the carbon network resulted in the dramatic evolution of growth morphology: from a 'buried' porous layer observed at low nitrogen incorporation to aligned bundles of nanorods grown perpendicular to the substrate surface at maximum discharge power and nitrogen flow. The films deposited at the low discharge power and high nitrogen incorporation exhibited a mesoporous sponge-like morphology after vacuum annealing. Relevant physical mechanisms responsible for the formation of nano- and mesoshaped morphology are discussed in terms of the effects of internal mechanical stresses and plasma etching. In addition, the sensing properties of the sponge-like layer were preliminarily examined in water vapor and ammonia ambients. The CN x films showed enhanced sensitivity to ammonia and reverse electrical response to moisture in comparison with a nitrogen-free nanoporous carbon film, which were assigned to modification of the electronic properties of the nitridated surface. [ABSTRACT FROM AUTHOR]

Initial porous silicon (por‐Si), carbonized porous silicon (por‐Si:C), and carbon‐incorporated porous silicon oxide (por‐SiO2:C) layers are studied by electron paramagnetic resonance (EPR) at T = 10–13 K. Scanning transmission electron microscopy and electron energy loss (EEL) spectroscopy show that por‐Si:C and por‐SiO2:C layers have a highly disordered structure with mixing sp2 and sp3 CC bonds. In the por‐SiO2:C layers, the peak of the oxygen bonded to carbon in the form of hydroxyl groups is found in the EEL spectrum of the C K‐edge region. Low‐intensity signals of Lorentzian lineshape are detected in the EPR spectrum of por‐Si, por‐Si:C, por‐SiO2:C layers. One of them is attributed to the Pb0 defect at the Si/SiO2 interface of nanocrystalline grain and the second to the silicon dangling bonds (SiDB) localized in nanocrystalline Si. The carbonization of por‐Si layers and subsequent oxidation of por‐Si:C gives rise to the appearance of additional EPR signals of high intensity at g = 2.0035(3) in por‐Si:C and at g = 2.0030(3) in por‐SiO2:C, which are assigned to carbon‐related defects (CRD) and carbon clusters, correspondingly. It was found that predominant defect types in por‐Si:C and por‐SiO2:C layers are CRD and carbon clusters, respectively, while the spin concentration of Pb0 interface defects and SiDB is low. [ABSTRACT FROM AUTHOR]

The effect of hydration procedure of fumed silica precursor on photoluminescent properties of carbonized silica (SiO2:C) nanocomposite after chemo/thermal treatments is studied. Main structural effect is the formation of chemical bonding of phenyl groups to silica surface via multiple CSiO bonding bridges. Synthesized samples demonstrate very broad photoluminescence (PL) bands in near ultraviolet and visible ranges with maximum intensity dependent on temperature of thermal annealing. Two main trends in luminescence properties are: 1) hydration‐induced blue shift of PL in comparison with PL of unhydrated series; 2) red shift of PL bands with increasing synthesis temperature regardless hydration procedure. Temperature dependent evolution of light emission bands is discussed in terms of surface carbon nanoclusters formation and aggregation processes. It is assumed that blue shift of PL bands in the hydrated series is associated with the decreased surface mobility of carbon atoms and clusters as a result of increased chemical bonding with silica surface that slows down carbon thermally stimulated clusterization/aggregation processes. Broad band photoluminescence of carbon nanoprcipitates dispersed in fumed silica is studied. The effects of silica surface pretreatment and pyrolysis of PhTMS grafted to silica surface on near UV and VIS emission are discussed in term of surface mobility and surfac. [ABSTRACT FROM AUTHOR]