Search results for "electronics"
showing 10 items of 4340 documents
Nonlinear photo-oxidation of graphene and carbon nanotubes probed by four wave mixing imaging and spectroscopy (Presentation Recording)
2015
Graphene has high potential for becoming the next generation material for electronics, photonics and optoelectronics. However, spatially controlled modification of graphene is required for applications. Here, we report patterning and controlled tuning of electrical and optical properties of graphene by laser induced non-linear oxidation. We use four wave mixing (FWM) as a key method for imaging graphene and graphene oxide patterns with high sensitivity. FWM produces strong signal in monolayer graphene and the signal is highly sensitive to oxidation providing good contrast between patterned and non-patterned areas. We have also performed photo-oxidation and FWM imaging for air suspended carb…
Metal thin-film temperature sensor embedded in heat-sink for CPV cells characterization
2014
The efficiency of a photovoltaic cell is dependent on its temperature, for this reason an accurate measurement of this parameter is important to fully characterize the device and to optimize its performance. For CPV applications a significant heat flux is needed to remove excess heat from the cell towards a heat sink, making it difficult to derive the cell temperature. In fact, measurements performed directly between the cell and the heat-sink, by use of commercial bulk sensors, would produce a significant disturbance in the heat flow; on the other hand, a measurement performed out of the cell / heat sink axis would be subject to large uncertainties, due to the high radial temperature gradi…
Functionalisation of MoS2 2D layers with diarylethene molecules
2021
Functionalisation of two dimensional (2D) materials with stimuli-responsive molecules has been scarcely investigated. Here, MoS2 layers obtained by chemical exfoliation are covalently and non-covalently functionalised using two photoswitchable diarylethene derivatives under their open- and closed-ring isomers. The choice of these light-responsive molecules is based on their excellent thermal irreversibility and fatigue resistance. The characterisation of the resultant molecular/2D heterostructures proves the successful anchoring of the molecules by both approaches as well as the influence that the driving interaction has in the photoswitching behaviour of the diarylethene isomers after thei…
Hole-Transporting Materials for Perovskite Solar Cells Employing an Anthradithiophene Core
2021
A decade after the report of the first efficient perovskite-based solar cell, development of novel hole-transporting materials (HTMs) is still one of the main topics in this research field. Two of the main advance vectors of this topic lie in obtaining materials with enhanced hole-extracting capability and in easing their synthetic cost. The use of anthra[1,9-bc:5,10-b'c']dithiophene (ADT) as a flat π-conjugated frame for bearing arylamine electroactive moieties allows obtaining two novel highly efficient HTMs from very cheap precursors. The solar cells fabricated making use of the mixed composition (FAPbI3)0.85(MAPbBr3)0.15 perovskite and the novel ADT-based HTMs show power conversion effi…
Two-color holographic-grating formation in amorphous As_2S_3 films
1998
A detailed experimental study of the holographic gratings recorded in nonannealed amorphous As2S3 films by 514.5-nm light in the presence of 632.8-nm readout light is carried out. A strong influence of a continuous 632.8-nm readout is found. The dependences of the maximal first-order diffraction efficiency and the corresponding specific recording energy on the holographic grating period were studied in a wide range of periods from 0.40 to 70.0 μm for 2-yr-old films. The obtained results are discussed in terms of photoinduced structural changes, relaxational structural changes, photoinduced anisotropy, and photoinduced recharging of the localized states in the bandgap. The photoinduced sulph…
<title>Effects of light polarization and crystal orientation on the holographic recording efficiency in doped LiNbO<formula><inf>&l…
2008
The holographic recording efficiency in doped LiNbO3 crystals has been studied both experimentally and theoretically depending on the type of dope, on the recording geometry and on the polarizations of the recording and readout light.. The studied crystals can be arranged in the following order by their efficiency: LiNbO3:Cu, LiNbO3:Fe (yet having a smaller thickness and donor concentration than LiNbO3:Cu), LiNbO3:Fe+Cu, LiNbO3:Fe+Ti, LiNbO3:Ti. It was found that the recording geometry with the holographic grating vector along the optical axis is much more efficient than in the perpendicular configuration.This fact is in accordance with the photorefraction theory based on photogalvanic and …
Submicrometer-Sized Roughness Suppresses Bacteria Adhesion.
2020
Biofilm formation is most commonly combatted with antibiotics or biocides. However, proven toxicity and increasing resistance of bacteria increase the need for alternative strategies to prevent adhesion of bacteria to surfaces. Chemical modification of the surfaces by tethering of functional polymer brushes or films provides a route toward antifouling coatings. Furthermore, nanorough or superhydrophobic surfaces can delay biofilm formation. Here we show that submicrometer-sized roughness can outweigh surface chemistry by testing the adhesion of E. coli to surfaces of different topography and wettability over long exposure times (>7 days). Gram-negative and positive bacterial strains are tes…
Wetting behavior of solid hydrogen films
1996
We have studied the dewetting of quench-condensed solid hydrogen films on bare and Ne plated Ag substrates. Information about the morphology of the films during the dewetting process is obtained from measurements of photoelectron tunneling through the films and complementary surface plasmon resonance data. Plating the Ag substrate with Ne films of various thickness allows to tune the strength of the van der Waals interaction with the hydrogen and thus to change the H2 films from a state of incomplete to complete wetting.
Dopant radial inhomogeneity in Mg-doped GaN nanowires
2018
International audience; Using atom probe tomography, it is demonstrated that Mg doping of GaN nanowires grown by Molecular Beam Epitaxy results in a marked radial inhomogeneity, namely a higher Mg content in the periphery of the nanowires. This spatial inhomogeneity is attributed to a preferential incorporation of Mg through the m-plane sidewalls of nanowires and is related to the formation of a Mg-rich surface which is stabilized by hydrogen. This is further supported by Raman spectroscopy experiments which give evidence of Mg-H complexes in the doped nanowires. A Mg doping mechanism such as this, specific to nanowires, may lead to higher levels of Mg doping than in layers, boosting the po…
Pulsed laser cleaning of oxidized metallic surfaces in electrochemically controlled liquid confinement
1997
Pulsed laser cleaning of oxidized metallic surfaces is studied. To our knowledge, for the first time, it has been demonstrated that the application of pulsed laser irradiation in a liquid confinement at controlled electrochemical potential enhances the oxide film removal from metal surfaces. Systematic studies on simulated corrosion product films using optical reflectance profile, energy dispersive X-ray spectroscopy, and piezoelectric transducer measurements, have revealed that efficient oxide film removal by laser irradiation is achieved if a basic electrolyte solution is used and a cathodic potential is imposed. The advantages of this novel technique against laser irradiation in air are …