Search results for "Amorphous solid"
showing 10 items of 622 documents
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…
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…
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…
Holographic recording in amorphous chalcogenide thin films
2003
A review of the recent advances and developments in the practical application of chalcogenide materials is presented, focusing special attention on holography and lithography using amorphous chalcogenide thin films.
Holographic recording in amorphous chalcogenide semiconductor thin films
2003
Abstract A detailed study of the amorphous As–S–Se and As2S3 films as recording media for optical holography and electron beam lithography is presented. The results of R&D on resist based on the amorphous As–S–Se thin films for manufacturing of embossed holographic labels are discussed. The holographic recording of transmission and Bragg gratings was studied.
Amorphous As–S–Se semiconductor resists for holography and lithography
2002
Abstract The photo- and electron-beam induced changes in solubility of thin films of the amorphous chalcogenide semiconductors As–S–Se and As 2 S 3 have been studied. The possibilities of practical application of these materials as resists for the production of relief holograms and holographic optical elements are discussed. It is shown that the self-enhancement (SE) phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light or thermal treatment can be used to increase the diffraction efficiency (DE) of the holograms.
<title>Amorphous chalcogenide semiconductor resists for holography and electron-beam lithography</title>
2001
The photo- and electron beam induced changes in solubility of amorphous chalcogenide semiconductor As-S-Se and As2S3 thin films have been studied. The possibilities of practical application of these materials as resists for the production of relief holograms and holographic optical elements are discussed. It is shown that the self-enhancement phenomenon of holographic recording in amorphous chalcogenide semiconductor films by light or thermal treatment can be used to increase the diffraction efficiency of the holograms.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.