1,721,147 research outputs found
XPS study of the FCuPc/SiO2 interface
No full textWe have studied the interaction between the hexadecafluoro-copper-phthalocyanine molecules and the SiO2 surface by means of the X-ray photoemission spectroscopy. The measurements have been done at high electron emission angle in order to enhance the surface sensitivity. Molecular films with different thicknesses have been deposited by thermal evaporation on clean SiO2 surface. When a sub-monolayer molecular film is deposited the formation of a very thin clean silicon layer at the, sample surface, because of the effects of the fluorine atoms, is observed. This interaction also determines the breaking of the first molecules at the substrate surface and the growth of a rich-carbon thin film. The following molecules form a bulk-like film. (C) 2003 Elsevier Science B.V. All rights reserved
Photoemission investigation on copper phthalocyanine : fullerene blend film
No full textThe electronic structure of thin blend films composed by copper phthalocyanine (CuPc) and fullerene (C-60) have been studied by soft x-ray photoemission spectroscopy. Several samples with different C-60/CuPc concentration ratios were prepared by thermal evaporation in ultrahigh vacuum conditions. As the C-60 concentration increases, strong shifts of the CuPc highest occupied molecular orbital (HOMO) level towards the Fermi level and of the C-60 HOMO level to higher binding energies have been observed. This experimental result suggests that there is a sizeable interaction between CuPc and C-60 molecules that can be interpreted in terms of a charge transfer from C-60 to CuPc. These shifts play an important role in the application of the CuPc:C-60 blend films for instance in the construction of solar cells on flexible substrates
Growth and electronic structure of CuFPc on Si(100)
No full textThe stability of hexadecafluoro copper phthalocyanine ultrathin films after the deposition onto clean Si(1 0 0)2 x 1 substrate has been studied by means of X-ray and ultraviolet photoemission spectroscopies. In particular the nature of a strong metallic Cu 2p component in the monolayer regime film has been investigated. These data have been compared with the results acquired on a thick film deposited on SiO2 substrate before and after an in situ thermal annealing. The valence band features indicate that the bulk-like molecular electronic structure is already present even at monolayer stage. Instead, when the annealed film presents the metallic Cu 2p structure, the molecular structure is completely destroyed. This indicates that the metallic component in the Cu 2p Spectrum is not due to the loss of the Cu atom during the deposition but can be attributed to the screening of the Cu 2p core hole by the high density of electrons at the Si(1 0 0)2 x 1 surface. (C) 2002 Elsevier Science B.V. All rights reserved
Interaction of naphthalocyanine with oxygen and with Si(111)7x7: an in situ X-Ray photoelectron spectroscopy study
No full textWe present a series of X-ray photoelectron spectroscopy experiments performed on the naphthalocyanine/Si(111)7 x 7 interface. The samples have been prepared in situ with two nominal thicknesses, one of these corresponding to submonolayer deposition. The organic thin films have been doped by varying the oxygen exposure during their growth. An integer ratio of the estimated oxygen atoms per naphthalocyanine (NPC) molecule in the quantitative XPS elemental analysis of the spectra provides evidence of preferential adsorption of oxygen in molecular form onto NPC. A careful analysis of the spectra indicates that oxygen mainly interacts with the inner porphyrin structure of the molecule. The substrate has been observed to influence the spectra only at the submonolayer stage of NPC deposition and at the lowest measured oxygen amount: the effect is a charge transfer from the Si(111)7 x 7 metallic substrate preferentially to the outer benzenic ring of the cross-shaped molecule. (C) 1999 Elsevier science B.V. All rights reserved
Micro-flow immunosensor based on thin-film interdigitated gold array microelectrodes for cancer biomarker detection
No full textIn this paper, we reported the development of a micro-flow label-free impedimetric biosensor based on the use of thin-film interdigitated gold array microelectrodes (IDA) for the detection of carbohydrate antigen 125 (CA125). The immunosensor is developed through the electropolymerization of anthranilic acid (AA) on the surface of IDA electrodes followed by the covalent attachment of anti-CA125 monoclonal antibody. CA125 protein affinity reaction was then evaluated by means of electrochemical impedance spectroscopy (EIS). The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using the optimized experimental conditions, the developed immunosensor showed a good analytical performance for CA125 detection from 0 to 100 U/mL with estimated limit of detection (LOD = 3Sblank/Slope) of 7 U/mL
RT growth of acetonitrile and acrylonitrile on Si(001)-2 x 1 studied by XPS and LEED
No full textIn this work we show the adsorption of acetonitrile (CH3CN) and acrylonitrile (CH2CHCN) on Si(0 0 1)-2 x 1 at room temperature by increasing the molecular doses. Especially, by means of XPS and LEED data, we stress the action of these molecules on the silicon surface locating the dangling-bonds quasi-saturation within 10 L. The shortage of nitrogen XPS signal and some anomalies in carbon spectra point to an invading action from a traditional X-ray source (Al-K-alpha line) against chemisorbed molecules. In particular, we think that a long exposure to this radiation could break carbon-silicon bonds changing some adsorption geometries and making desorb molecular fragments. (C) 2003 Elsevier B.V. All rights reserved
Soft X-ray photoemission spectroscopy study on the interaction between CuFPc molecules and Si(1 1 1)7×7 surface
No full textHigh resolution soft X-ray photoemission measurements have been performed onto ultra thin films of hexadecafluoro copper phthalocyanine deposited, at room temperature and in ultra high vacuum conditions, onto clean Si(111)7 x 7 substrate. The Si 2p spectra show the missing of the adatoms signal and the appearance of a broad feature mainly due to F-Si bonds. The Si 2p spectrum allows us to exclude the loss of copper atom from the molecule during the deposition. C Is spectrum evidences the presence of Si-C interaction, These results confirm previously published X-ray photoemission spectroscopy fluorine spectra, which clearly present the effects of the interaction of F atoms of the molecule with the silicon substrate and a strong modification of the C Is spectrum. (C) 2001 Elsevier Science B.V. All rights reserved
N-Doped TiO2 Nanofibers Deposited by Electrospinning
No full text"N-doped TiO2 nanofibers were deposited by electrospinning onto silicon and then annealed in air. They have been analyzed by secondary electron microscopy, X-ray diffraction, and X-ray photo:mission. After the thermal processes, the fibers, having a diameter between 300 and 400 nm, contain a small amount of nitrogen and still;how the TiO2 anatase crystalline structure. Different solutions and annealing processes were used to vary the nitrogen concentration and the crystalline phase. These nanofibers were successfully tested as photocatalytic devices for methylene blue degradation under visible light irradiation.
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