Search results for "Surfaces"
showing 10 items of 2837 documents
Gas sensitive luminescence of ZnO coatings obtained by plazma electrolytic oxidation
2015
Abstract The ZnO coatings on Zn substrate were obtained using plasma electrolytic oxidation method. The XRD and SEM methods were used for structural and morphological characterization of obtained coatings. The luminescence of ZnO coatings were studied and compared with luminescence characteristics of ZnO single crystal. It is shown that luminescence intensity in ZnO defect band depends on oxygen concentration in ambient atmosphere. The effect is of interest for oxygen sensing based on ZnO coating luminescence.
Tunability by alkali metal cations of photoinduced charge separation in azacrown functionalized graphene.
2013
A modified graphene oxide containing aza-9-crown-3 ether units covalently anchored has been prepared; aqueous suspensions of this material in the presence of Li(+), Na(+) and K(+) cations exhibit enhanced electrochemical response, enhanced photoinduced charge separation and longer lifetimes, facts that can be attributed to stabilization of electrons on graphene oxide by the nearby alkali metal cation-azacrown complexes.
Factors Controlling the Energy of Nitrogen Monolayer Coverage onHigh Surface Area Catalyst Oxide Carriers
2011
Factors affecting the strength of nitrogen physisorption at monolayer coverage on different catalytic oxide carriers (e.g., ZnO, MgO, Al2O3, ZrO2, TiO2, and SiO2) have been addressed. Isotherm elaboration by the two-parameter BET equation provides C-constant values (80–200) inversely related to the polarizing power (PP) of the oxide adsorbent irrespective of the surface area exposure. The energy of monolayer formation depends on the extent of charge-delocalization characterizing the surface cation-oxygen bond, which determines the acid–base character of the oxide and strength of van der Waals interactions with adsorbate molecules. Density functional theory (DFT) calculations on MgO and TiO2…
Interdependence of structural and electrical properties in tantalum/tantalum oxide multilayers
2013
International audience; Dc reactive sputtering was used to deposit tantalum metal/oxide periodic nanometric multilayers using the innovative technique namely, the reactive gas pulsing process (RGPP). Different pulsing periods were used for each deposition to produce metal-oxide periodic alternations included between 5 and 80 nm. Structure, crystallinity and chemical composition of these films were systematically investigated by Transmission Electron Microscopy (TEM) and Energy-dispersive X-ray (EDX) spectroscopy techniques. Moreover, electrical properties were also studied by the Van der Pauw technique.
Reaction pathways for atomic layer deposition with lithium hexamethyl disilazide, trimethyl phosphate, and oxygen plasma
2020
Atomic layer deposition (ALD) of lithium-containing films is of interest for the development of next-generation energy storage devices. Lithium hexamethyl disilazide (LiHMDS) is an established precursor to grow these types of films. The LiHMDS molecule can either be used as a single-source precursor molecule for lithium or as a dual-source precursor molecule for lithium and silicon. Single-source behavior of LiHMDS is observed in the deposition process with trimethylphosphate (TMP) resulting in the deposition of crystalline lithium phosphate (Li3PO4). In contrast, LiHMDS exhibits dual-source behavior when combined with O2 plasma, resulting in a lithium silicate. Both processes were characte…
A photoemission study of molybdenum hexacarbonyl adsorption and decomposition on TiO2(110) surface.
2007
International audience; The adsorption and decomposition of molybdenum hexacarbonyl on (110) TiO2 surfaces were studied using both core levels and valence band photoemission spectroscopies. It was found that after an adsorption at 140 K, when going back to room temperature, only a small part of molybdenum compounds, previously present at low temperature, remained on the TiO2 surface. This indicates that the desorption temperature on such a surface is lower than the decomposition one. The use of photon irradiation to decompose the hexacarbonyl molecule was also studied. It was shown that during such a decomposition molecular fragments were chemisorbed on the surface allowing a higher amount …
Modulation of the solubility of luminescent semiconductor nanocrystals through facile surface functionalization
2014
The solubility of luminescent quantum dots in solvents from hexane to water can be finely tuned by the choice of the countercations associated with carboxylate residues present on the nanocrystal surface. The resulting nanocrystals exhibit long term colloidal and chemical stability and maintain their photophysical properties.
Structural and electrical properties in tungsten/tungsten oxide multilayers
2014
International audience; Tungsten and tungsten oxide periodic nanometric multilayers have been deposited by DC reactive sputtering using the reactive gas pulsing process. Different pulsing periods have been used for each deposition to produce metal-oxide periodic alternations ranging from 3.3 to 71.5 nm. The morphology, crystallinity and chemical composition of these films have been investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. The produced multilayers exhibited an amorphous structure and the composition stability of WO3 sub-layers has been pointed out. Moreover, electrical properties have also been studied by the van der Pauw technique…
Mesoporous ZnFe2O4@TiO2 Nanofibers Prepared by Electrospinning Coupled to PECVD as Highly Performing Photocatalytic Materials
2017
International audience; Zinc ferrite @ titanium dioxide (ZnFe2O4@TiO2) composite nanofibers were elaborated by combining the two different techniques: electrospinning and plasma-enhanced chemical vapor deposition (PECVD). The nanofiber compositions were controlled using different ratios of zinc to iron. Their structural, morphological, and optical properties were analyzed by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, BET surface area, Raman spectroscopy, and UV–visible spectrophotometry. The photocatalytic activity has been investigated by the degradation of methylene blue under visible light. The results indicate that the combination of spinel st…
Monolithic integration of Giant Magnetoresistance (GMR) devices onto standard processed CMOS dies
2014
Giant Magnetoresistance (GMR) based technology is nowadays the preferred option for low magnetic fields sensing in disciplines such as biotechnology or microelectronics. Their compatibility with standard CMOS processes is currently investigated as a key point for the development of novel applications, requiring compact electronic readout. In this paper, such compatibility has been experimentally studied with two particular non-dedicated CMOS standards: 0.35 μm from AMS (Austria MicroSystems) and 2.5 μm from CNM (Centre Nacional de Microelectrònica, Barcelona) as representative examples. GMR test devices have been designed and fabricated onto processed chips from both technologies. In order …