Promising properties of ALD boron nitride nanotube mats for water purification

International audienc

Labeling and monitoring the distribution of anchoring sites on functionalized CNTs by atomic layer deposition

The chemical inertness of graphite and, in the case of tubes, of rolled up few layer graphene sheets, requires some degree of “defect engineering” for the fabrication of carbon based heterostructured materials. It is shown that atomic layer deposition provides a means to specifically label anchoring sites and can be used to characterize the surface functionality of differently treated carbon nanotubes. Direct observation of deposited titania by analytical transmission electron microscopy reveals the location and density of anchoring sites as well as structure related concentrations of functional groups on the surface of the tubes. Controlled functionalization of the tubes therefore allows us to tailor the distribution of deposited material and, hence, fabricate complex heterostructures

MOx/CNTs Hetero-Structures for Gas Sensing Applications: Role of CNTs Defects

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Anomalous C-V response correlated to relaxation processes in TiO2 thin film based-metal-insulator-metal capacitor: Effect of titanium and oxygen defects

Capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements are performed on atomic layer deposited TiO2 thin films with top and bottom Au and Pt electrodes, respectively, over a large temperature and frequency range. A sharp capacitance peak/discontinuity (C-V anomalous) is observed in the C-V characteristics at various temperatures and voltages. It is demonstrated that this phenomenon is directly associated with oxygen vacancies. The C-V peak irreversibility and dissymmetry at the reversal dc voltage are attributed to difference between the Schottky contacts at the metal/TiO2 interfaces. Dielectric analyses reveal two relaxation processes with degeneration of the activation energy. The low trap level of 0.60-0.65 eV is associated with the first ionized oxygen vacancy at low temperature, while the deep trap level of 1.05 eV is associated to the second ionized oxygen vacancy at high temperature. The DC conductivity of the films exhibits a transition temperature at 200 degrees C, suggesting a transition from a conduction regime governed by ionized oxygen vacancies to one governed by interstitial Ti3+ ions. Both the C-V anomalous and relaxation processes in TiO2 arise from oxygen vacancies, while the conduction mechanism at high temperature is governed by interstitial titanium ions. (C) 2015 AIP Publishing LLC

ALD pour des applications capteurs, biocapteurs et membranes

International audiencePerformances of sensors, biosensors and membranes as well as their selectivity are dependent of the structuration, morphology and type of the used material. Atomic layer deposition (ALD) appears as a suitable synthesis technique due to its simplicity, reproducibility, the atomic scale precision of the deposited thickness and high homogeneity of the obtained films. This article deals with the use of ALD for fabricating sensors, biosensors and membranes and presents some achievements in sensing and separation. The advantages of the technique compared to common ones are highlighted using few examples taken from the literature.Les performances des capteurs, biocapteurs et membranes ainsi que leurs sélectivités dépendent de la structuration, de la morphologie et de la nature des matériaux utilisés. La technique de dépôt par couche atomique ou ALD apparaît comme une technique de fabrication de choix du fait de sa simplicité, de sa reproductibilité, de l'homogénéité des dépôts obtenus, même sur des substrats très structurés, ainsi que de la possibilité de contrôle de leur épaisseur au niveau atomique. Cet article présente l'utilisation de l'ALD pour la fabrication de capteurs, biocapteurs et membranes avec les réalisations possibles en termes de détection et de séparation. L'avantage de cette technique par rapport à des approches plus conventionnelles est mise en évidence par quelques exemples choisis dans la littérature

MOx/CNTs Hetero-Structures for Gas Sensing Applications: Role of CNTs Defects

AbstractThe preparation, characterization and sensing properties of CNT composites with a thin metal oxide (MOx) surface layer is presented. Atomic layer deposition (ALD) was applied for the coating of the inner and outer CNTs walls with thin films of ZnO and SnO2 of precisely controlled thicknesses. Differently treated CNTs with different degree of surface functionalization were used as support for the oxide films. The sensing properties of the obtained composite materials towards NO2 were investigated and related to the morphological and microstructural characteristics of both the coating and support. SnO2-based composites on CNTs treated at 700°C show enhanced performance as sensors, making them suitable for practical applications

Atomic layer deposition of stable 2D materials

International audienc

Gas sensing properties and p-type response of ALD TiO2 coated carbon nanotubes

Amorphous titanium dioxide-coated carbon nanotubes (CNTs) were prepared by atomic layer deposition (ALD) and investigated as sensing layers for resistive NO2 and O-2 gas sensors. By varying ALD process conditions and CNT structure, heterostructures with different metal oxide grain size, morphology and coating thickness were synthesized. Higher responses were observed with homogeneous and continuous 5.5 nm thick films onto CNTs at an operating temperature of 150 degrees C, while CNTs decorated with either discontinuous film or TiO2 nanoparticles showed a weak response close to the one of device made of bare CNTs. An unexpected p-type behavior in presence of the target gas was also noticed, independently of the metal oxide morphology and thickness. Based on previous works, hypotheses were made in order to explain the p-type behavior of TiO2/CNT sensors