0000000000068857
AUTHOR
A. La Magna
Micro-Raman characterization of graphene grown on SiC(000-1)
Graphene (Gr) was grown on the C face of 4H-SiC under optimized conditions (high annealing temperatures ranging from 1850 to 1950°C in Ar ambient at 900 mbar) in order to achieve few layers of Gr coverage. Several microscopy techniques, including optical microscopy (OM), ?Raman spectroscopy, atomic force microscopy (AFM) and atomic resolution scanning transmission electron microscopy (STEM) have been used to extensively characterize the lateral uniformity of the as-grown layers at different temperatures. ?Raman analysis provided information on the variation of the number of layers, of the stacking-type, doping and strain.
Study of the role of particle-particle dipole interaction in dielectrophoretic devices for biomarkers identification
A three dimensional Coupled Monte Carlo-Poisson method has been used to evaluate the impact of particle-particle dipole interactions in the equilibrium distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. We compare the simulated distributions with experimental ones both for micro- (MDA-MB-231 breast tumor cells) and nano-(multiwall carbon nanotubes) particles. In both cases the equilibrium distributions near the electrodes are dominated by dipole interactions which locally enhance the DEP effect and promote long particles chains.
Reduction of thermal damage in ultrathin gate oxides after intrinsic dielectric breakdown
We have compared the thermal damage in ultrathin gate SiO2 layers of 5.6 and 3 nm thickness after intrinsic dielectric breakdown due to constant voltage Fowler-Nordheim stress. The power dissipated through the metal-oxide-semiconductor capacitor during the breakdown transient, measured with high time resolution, strongly decreases with oxide thickness. This is reflected in a noticeable reduction of the thermal damage found in the structure after breakdown. The effect can be explained as the consequence of the lower amount of defects present in the oxide at the breakdown instant and of the occurrence of a softer breakdown in the initial spot. The present data allow us to estimate the power t…
Interfacial disorder of graphene grown at high temperatures on 4H-SiC(000-1)
This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 ºC) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy showed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr gro…
Theoretical and experimental study of the kinetics of particle chains near electrodes in dielectrophoretic devices
Using a three dimensional coupled Monte Carlo-Poisson algorithm and experimental results we studied the role of the particle-particle dipole interaction on the kinetics of a system of human cells suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. We found that the kinetics of the cells during negative/repulsive dielectrophoresis depends on the local distribution of particles. If the cells have generated long chains during positive/attractive dielectrophoresis, such chains can hinder subsequent detachment resulting in a reduction of the separation/manipulation efficiency of dielectrophoretic device. This effec…
Graphene p-Type Doping and Stability by Thermal Treatments in Molecular Oxygen Controlled Atmosphere
Doping and stability of monolayer low defect content graphene transferred on a silicon dioxide substrate on silicon are investigated by micro-Raman spectroscopy and atomic force microscopy (AFM) during thermal treatments in oxygen and vacuum controlled atmosphere. The exposure to molecular oxygen induces graphene changes as evidenced by a blue-shift of the G and 2D Raman bands, together with the decrease of I2D/IG intensity ratio, which are consistent with a high p-type doping (∼1013 cm-2) of graphene. The successive thermal treatment in vacuum does not affect the induced doping showing this latter stability. By investigating the temperature range 140-350 °C and the process time evolution, …