Search results for "amorphous"
showing 10 items of 790 documents
Role of the Back Metal-Semiconductor Contact on the Performances of a-Si:H Solar Cells
2011
We have investigated the role of the metal-semiconductor back contact on the performances of thin film modules consisting of single junction a-Si:H photovoltaic (PV) cells deposited with p-i-n configuration. We find that an adequate choice of the back contact helps reducing the barrier height of the junction improving the contact conductivity. For this purpose Mo has shown to be effective. Moreover we find that Mo, as refractory material, has additional beneficial effects reducing the formation of defects leading to the decrease of recombination losses. We have then fabricated a PV module on flexible substrate for indoor energy harvesting applications using Mo as back contact. An efficiency…
Carrier transport mechanism in the SnO(2):F/p-type a-Si:H heterojunction
2011
We characterize SnO(2):F/p-type a-Si:H/Mo structures by current-voltage (I-V) and capacitance-voltage (C-V) measurements at different temperatures to determine the transport mechanism in the SnO2:F/p-type a-Si:H heterojunction. The experimental I-V curves of these structures, almost symmetric around the origin, are ohmic for vertical bar V vertical bar< 0:1 V and have a super-linear behavior (power law) for vertical bar V vertical bar < 0:1 V. The structure can be modeled as two diodes back to back connected so that the main current transport mechanisms are due to the reverse current of the diodes. To explain the measured C-V curves, the capacitance of the heterostructure is modeled as the …
Raman signal reveals the rhombohedral crystallographic structure in ultra-thin layers of bismuth thermally evaporated on amorphous substrate
2021
Under the challenge of growing a single bilayer of Bi oriented in the (111) crystallographic direction over amorphous substrates, we have studied different thicknesses of Bi thermally evaporated onto silicon oxide in order to shed light on the dominant atomic structures and their oxidation. We have employed atomic force microscope, X-ray diffraction, and scanning electron microscope approaches to demonstrate that Bi is crystalline and oriented in the (111) direction for thicknesses over 20 nm. Surprisingly, Raman spectroscopy indicates that the rhombohedral structure is preserved even for ultra-thin layers of Bi, down to $\sim 5$ nm. Moreover, the signals also reveal that bismuth films expo…
Amorphous and crystalline polyetheretherketone: Mechanical properties and tissue reactions during a 3-year follow-up.
2007
The study was aimed to test the mechanical strength, structural stability, and tissue reactions of optically amorphous and crystalline polyetheretherketone (PEEK) plates during a 3-year follow-up in vivo and in vitro. The injection-moulded PEEK plates were implanted to the dorsal subcutis of 12 sheep, which were sacrificed at 6-156 weeks. Thereafter, the plates were subjected to tensile tests, and levels of crystallinity were assessed by differential scanning calorimetry (DSC). Histological evaluation was carried out using the paraffin technique. In vitro properties were examined with the tensile test and DSC at 0-156 weeks. Tissue reactions were mild and fairly similar for the amorphous an…
From crystal to glass-like thermal conductivity in crystalline minerals
2015
Équipe 103 : Composés intermétalliques et matériaux hybrides; International audience; The ability of some materials with a perfectly ordered crystal structure to mimic the heat conduction of amorphous solids is a remarkable physical property that finds applications in numerous areas of materials science, for example, in the search for more efficient thermoelectric materials that enable to directly convert heat into electricity. Here, we unveil the mechanism in which glass-like thermal conductivity emerges in tetrahedrites, a family of natural minerals extensively studied in geology and, more recently, in thermoelectricity. By investigating the lattice dynamics of two tetrahedrites of very c…
Layered-Expanded Mesostructured Silicas: Generalized Synthesis and Functionalization
2018
Mesostructured layered silicas have been prepared through a surfactant-assisted procedure using neutral alkylamines as templates and starting from atrane complexes as hydrolytic inorganic precursors. By adjusting the synthetic parameters, this kinetically controlled reproducible one-pot method allows for obtaining both pure and functionalized (inorganic or organically) lamellar silica frameworks. These are easily deconstructed and built up again, which provides a simple way for expanding the interlamellar space. The materials present high dispersibility, which results in stable colloidal suspensions.
Engineering of Nanofibrous Amorphous and Crystalline Solid Dispersions for Oral Drug Delivery
2018
Poor aqueous solubility (<0.1 mg/mL) affects a significant number of drugs currently on the market or under development. Several formulation strategies including salt formation, particle size reduction, and solid dispersion approaches have been employed with varied success. In this review, we focus primarily on the emerging trends in the generation of amorphous and micro/nano-crystalline solid dispersions using electrospinning to improve the dissolution rate and in turn the bioavailability of poorly water-soluble drugs. Electrospinning is a simple but versatile process that utilizes electrostatic forces to generate polymeric fibers and has been used for over 100 years to generate synthet…
Room-Temperature Micropillar Growth of Lithium-Titanate-Carbon Composite Structures by Self-Biased Direct Current Magnetron Sputtering for Lithium Io…
2019
Here, an unidentified type of micropillar growth is described at room temperature during conventional direct-current magnetron sputtering (DC-MS) deposition from a Li4Ti5O12+graphite sputter target under negative substrate bias and high operating pressure. These fabricated carbon-Li2O-TiO2 microstructures consisting of various Li4Ti5O12/Li2TiO3/LixTiO2 crystalline phases are demonstrated as an anode material in Li-ion microbatteries. The described micropillar fabrication method is a low-cost, substrate independent, single-step, room-temperature vacuum process utilizing a mature industrial complementary metal-oxide-semiconductor (CMOS)-compatible technology. Furthermore, tentative considerat…
Formation of anodic films on sputtering-deposited Al–Hf alloys
2009
Abstract The growth of barrier-type anodic films at high efficiency on a range of sputtering-deposited Al–Hf alloys, containing from 1 to 95 at.% Hf, has been investigated in ammonium pentaborate electrolyte. The alloys encompassed nanocrystalline and amorphous structures, the latter being produced for alloys containing from 26 to 61 at.% Hf. Except at the highest hafnium content, the films were amorphous and contained units of HfO 2 and Al 2 O 3 distributed relatively uniformly through the film thickness. Boron species were confined to outer regions of the films. The boron distributions suggest that the cation transport number decreases progressively with increasing hafnium concentration i…
<title>Holographic recording in amorphous chalcogenide semiconductor thin films</title>
2000
ABSTRACT The photoinduced changes ofoptical properties and holographic recording in amorphous chalcogenide semiconductor As-S- Se and As2S3 thin films have been studied. The possibilities of the practical applications of these materials as the photoresists for the production of the relief holograms and holographic optical elements are discussed. It is shown that theself-enhancement phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light orthermal treatment can be used to increase the diffraction efficiency ofthe holograms.Keywords: chalcogenide semiconductors, amorphous films, photoresists, photoinduced processes, relaxation processes,self-enhancement of h…