Graphene functionalised by laser ablated V2O5 as highly sensitive NH3 sensor

Graphene has been recognized as a promising gas sensing material. The response of graphene-based sensors can be radically improved by introducing defects in graphene using, e. g., metal or metal oxide nanoparticles. We have functionalised CVD grown, single layer graphene by applying pulsed laser deposition (PLD) of V2O5 which resulted in a thin V2O5 layer on graphene with average thickness of ~0.6 nm. According to Raman analysis, PLD process also induced defects in graphene. Compared to unmodified graphene, the obtained chemiresistive sensor showed considerable improvement of sensing ammonia at room temperature. In addition, also the response time, sensitivity and reversibility were essentially enhanced due to graphene functionalisation by laser deposited V2O5. This can be explained by increased surface density of gas adsorption sites introduced by high energy atoms in laser ablation plasma and formation of nanophase boundaries between deposited V2O5 and graphene.Comment: 22 pages, 6 figure

Atomic layer deposition of high-k oxides on graphene

Atomic layer deposition of high-k oxides on graphene.Comment: Graphene - Synthesis, Characterization, Properties and Applications, Jian Ru Gong (Ed.), ISBN: 978-953-307-292-0, InTech, Available from: http://www.intechopen.com/articles/show/title/atomic-layer-deposition-of-high-k-oxides-on-graphen

Vibrating wire measurements in superfluid He-3 at the melting curve down to 0.53 mK.

Measurements of the vibrating wire spectrum have been carried out in superfluid He-3 along the melting curve down to 0.53mK. We have observed that at temperatures below 0.3 T-c, the width of the mechanical resonance of the wire decreases exponentially with 1/T, indicating the ballistic regime of collisions with quasiparticles, The value of the superfluid energy gap was found to be (1.99+/-0.05) T-c, in good agreement with the values obtained from heat capacity measurements. The vibrating wire was thereby calibrated for further experiments at temperatures below 0.5 mK, where the sensitivity of the melting curve thermometry becomes rather poor

Surface of a He-3 crystal: Crossover from quantum to classical behavior.

He-3 crystals start to show facets on their surface only at about 100 mK, well below the roughening transition temperature. To understand the reason for that, we have performed the first quantitative investigation on the growth dynamics of the basic (110) facet at 60-110 mK. The obtained values of the step free energy suggest an extremely weak coupling of the solid-liquid interface to the crystal lattice which we show to be the result of quantum fluctuations of the interface. The renormalization group approach by Nozieres and Gallet, modified to incorporate quantum fluctuations, explains well the temperature dependence of the step energy measured in this work and at ultralow temperatures by Tsepelin et al., where the coupling is known to be strong. We have thus shown that, paradoxically, the role of quantum fluctuations is at higher temperatures much larger than at low temperature

Measurements on the surface tension of He-3 crystals near 100 mK.

He-3 crystals start to show facets on their surface only at about 100 mK, well below the roughening transition temperature, and the reason for this change of the surface state is not clear yet. However, the most important characteristic of the crystal surface, the surface tension, was not measured in this temperature range before. We report our observations on the equilibrium shape of the He-3 crystals in the temperature range of 77...110 mK. The surface tension was found to be isotropic and temperature-independent, and the corresponding value of the capillary length, lambda = 0.93 +/- 0.10 mm, is in a good agreement with the value measured at higher temperatures by Rolley et al