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Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures
Gabriele Fisichella,
Giuseppe Greco,
Patrick Fiorenza,
Salvatore Di Franco,
Fabrizio Roccaforte,
Filippo Giannazzo
Issue:
Volume 1, Issue 1, December 2015
Pages:
1-7
Received:
5 July 2015
Accepted:
28 July 2015
Published:
29 July 2015
DOI:
10.11648/j.nsnm.20150101.11
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Abstract: We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths
Abstract: We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these na...
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DLS Characterization of Non-Ionic Surfactant Vesicles for Potential Nose to Brain Application
Federica Rinaldi,
Patrizia N. Hanieh,
Carlotta Marianecci,
Maria Carafa
Issue:
Volume 1, Issue 1, December 2015
Pages:
8-14
Received:
7 July 2015
Accepted:
28 July 2015
Published:
29 July 2015
DOI:
10.11648/j.nsnm.20150101.12
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Abstract: The aim of this paper is the preparation and characterization of drug delivery systems for a potential brain delivery by intranasal administration. It is possible to reach the central nervous system with alternative routes through which therapeutic agents can bypass the blood brain barrier: that is the nasal administration. Intranasal drug administration is non-invasive and it could be a promising drug delivery method for patients who suffer from chronic and crippling Central Nervous System diseases. Among the formulation strategies for enhanced nose to brain drug delivery, the use of colloidal carriers has became a revolutionary approach. The success of a therapeutic strategy by using nanocarriers depends on their ability to entrap drugs, to penetrate through anatomical barriers, to efficiently release the incorporated drugs, to show a good stability in nanometric size range and good biocompatibility. The use of vesicular systems (niosomes), in nose to brain delivery is here presented. One of the major problems associated with nasal administration is the rapid removal of drugs or drug delivery systems, from the deposition site through mucociliary clearance. This effect is responsible of reduction of contact time between drug or drug delivery systems and nasal epithelium. This problem could be solved by coating nanocarriers with a mucoadhesive agent: chitosan. In this paper the preparation and characterization of hybrid niosomes by Tween 20 and Tween 21 together with dicetyl phosphate or Span 20 and the cationic polyelectrolyte chitosan are described in order to obtain intranasal drug delivery systems. In particular through dynamic light scattering, laser Doppler electrophoresis and fluorescence measurements the aggregation behavior between vesicles and polyelectrolyte can be monitored. Overall phenomenology is well described in terms of the re-entrant condensation and charge inversion behavior, observed in different colloidal systems. The physical stability of hybrid niosomes obtained by the three different surfactants was also evaluated
Abstract: The aim of this paper is the preparation and characterization of drug delivery systems for a potential brain delivery by intranasal administration. It is possible to reach the central nervous system with alternative routes through which therapeutic agents can bypass the blood brain barrier: that is the nasal administration. Intranasal drug administ...
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Surface Acoustic Waves in Thin Films Nanometrology
Issue:
Volume 1, Issue 1, December 2015
Pages:
15-19
Received:
13 July 2015
Accepted:
28 July 2015
Published:
29 July 2015
DOI:
10.11648/j.nsnm.20150101.13
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Abstract: Thin films nanometrology is an emerging field in nanoscience as the synthesis, processing and applications of nanostructured thin films require an in-depth knowledge of their elastic constants. The elastic energy of a surface acoustic wave propagating in a solid medium, is concentrated at the interface between the solid and air (or a sufficiently rarified medium); consequently, high frequency surface acoustic waves with sub-micrometer wavelengths are an extraordinary tool for a qualitative and quantitative elastic characterization of thin films. In this article, a short review is presented to describe the main ultrasound techniques based on surface acoustic waves for thin films characterization and to highlight the probing limits of acoustic nanometrology
Abstract: Thin films nanometrology is an emerging field in nanoscience as the synthesis, processing and applications of nanostructured thin films require an in-depth knowledge of their elastic constants. The elastic energy of a surface acoustic wave propagating in a solid medium, is concentrated at the interface between the solid and air (or a sufficiently r...
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Single Particle ICP-MS (SP-ICP-MS) For the Detection of Metal-Based Nanoparticles in Environmental Matrices: Application to Silver Nanoparticles in Surface Water
C. Stephan,
K. J. Wilkinson,
M. Hadioui
Issue:
Volume 1, Issue 1, December 2015
Pages:
20-23
Received:
14 July 2015
Accepted:
28 July 2015
Published:
29 July 2015
DOI:
10.11648/j.nsnm.20150101.14
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Abstract: The National Nanotechnology Initiative defines engineered nanomaterials (ENM) as those with dimensions of 1–100 nm, where their unique characteristics enable novel applications to be carried out. ENMs often possess different properties than their bulk counterparts of the same composition, making them of great interest for a broad spectrum of industrial, commercial, and health care uses. However, the widespread application of ENMs will inevitably lead to their release into the environment, which raises concerns about their potential adverse effects on the ecosystems and their impact on human health. This paper discusses the theory of Single Particle ICP-MS (SP-ICP-MS) and in particular, its use in characterizing, counting and sizing metal-based nanoparticles in Environmental Matrices. This breakthrough advancement in ICP-MS allows researchers to track the fate/transformation of nanoparticles in various matrices. Single Particle-ICP-MS allow the differentiation between ionic and particulate signals without any separation, measure particle concentration down to as low as 1000 particles/mL with great precision and determine particle size and size distribution. With fast sample analysis time, SP-ICP-MS is a key analytical technique in assessing the fate, behavior and distribution of ENMs in different sample Environmental Matrices.
Abstract: The National Nanotechnology Initiative defines engineered nanomaterials (ENM) as those with dimensions of 1–100 nm, where their unique characteristics enable novel applications to be carried out. ENMs often possess different properties than their bulk counterparts of the same composition, making them of great interest for a broad spectrum of indust...
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