Retraction: “Photo-induced changes in a hybrid amorphous chalcogenide/silica photonic crystal fiber” [Appl. Phys. Lett. 104, 011114 (2014)]
No abstract prepared.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
SEARCH · Engineering Papers
Results for “Amorphous”
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Low-temperature processable amorphous In-W-O thin-film transistors with high mobility and stability
Thin-film transistors (TFTs) with a high stability and a high field-effect mobility have been achieved using W-doped indium oxide semiconductors in a low-temperature process (∼150 °C). By incorporating WO{sub 3} into indium oxide, TFTs that were highly stable under a negative bias stress were reproducibly achieved without high-temperature annealing, and the degradation of the field-effect mobility was not pronounced. This may be due to the efficient suppression of the excess oxygen vacancies in the film by the high dissociation energy of the bond between oxygen and W atoms and to the different charge states of W ions.
36 MATERIALS SCIENCE↗
Light induced instability mechanism in amorphous InGaZn oxide semiconductors
A model of the negative bias illumination stress instability in InGaZn oxide is presented, based on the photo-excitation of electrons from oxygen interstitials. The O interstitials are present to compensate hydrogen donors. The O interstitials are found to spontaneously form in O-rich conditions for Fermi energies at the conduction band edge, much more easily that in related oxides. The excited electrons give rise to a persistent photoconductivity due to an energy barrier to recombination. The formation energy of the O interstitials varies with their separation from the H donors, which leads to a voltage stress dependence on the compensation.
36 MATERIALS SCIENCE↗
Electron-beam induced variation of surface profile in amorphous As{sub 20}Se{sub 80} films
Unusual profile variation of holographic surface relief gratings is detected in thin (2 μm) As{sub 20}Se{sub 80} chalcogenide films under e-beam irradiation: gratings of small periods were smoothed, whereas the gratings of larger periods increased their amplitudes. Irradiation was carried out in SEM, with 20 kV voltage and 8 nA current; the profiles of the irradiated areas were analyzed both by AFM and SEM. It is found that the kinetics of both flattening and growth followed by exponential law and took place due to lateral mass transport accelerated by e-irradiation. It is shown that the profile variation is mainly caused by competition between capillary forces and “chemical” forces induced by broken and deformed atomic bonds under e-beam irradiation. The kinetics of profile variation was calculated assuming that the mechanism of e-beam induced mass transfer is volume diffusion. The diffusion coefficients were estimated from the experimental data using theoretical expressions derived.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Robust topological surface states of Bi2Se3 thin films on amorphous SiO2/Si substrate and a large ambipolar gating effect
N/A
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Indium tin oxide/InGaZnO bilayer stacks for enhanced mobility and optical stability in amorphous oxide thin film transistors
Optically more stable, high mobility InGaZnO thin film transistors were fabricated by implementing ultrathin In{sub 2}O{sub 3}-SnO{sub 2} (ITO) layers at the gate dielectric/semiconductor interface. The optimized device portrayed a high saturation mobility of ∼80 cm{sup 2}/V s with off current values lower than 10{sup −11}A. The ITO layer also acted as a hole filter layer, and hole current and threshold voltage shift values measured under negative bias illumination conditions showed that a significant amount of photo-generated charge carriers were annihilated before reaching the gate insulator. This effect was more evident at larger intensities, showing threshold voltage shift values reduced by more than ∼70% under stress conditions.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy
Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ε{sup ´} and the dissipation factor Tan(δ). We prove that the evolution of the imaginary part of the complex permittivity against temperature ε{sup ′′}=f(T) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Q{sub p}(T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Stress effects on the elastic properties of amorphous polymeric materials
Brillouin light scattering measurements have been used to study the stress induced modification in the elastic properties of two glass forming polymers: polybutadiene and epoxy-amine resin, prototypes of linear and network polymers, respectively. Following the usual thermodynamic path to the glass transition, polybutadiene has been studied as a function of temperature from the liquid well into the glassy phase. In the epoxy resin, the experiments took advantage of the system ability to reach the glass both via the chemical vitrification route, i.e., by increasing the number of covalent bonds among the constituent molecules, as well as via the physical thermal route, i.e., by decreasing the temperature. Independently from the particular way chosen to reach the glassy phase, the measurements reveal the signature of long range tensile stresses development in the glass. The stress presence modifies both the value of the sound velocities and their mutual relationship, so as to break the generalized Cauchy-like relation. In particular, when long range stresses, by improvise sample cracking, are released, the frequency of longitudinal acoustic modes increases more than 10% in polybutadiene and ∼4% in the epoxy resin. The data analysis suggests the presence of at least two different mechanisms acting on different length scales which strongly affect the overall elastic behaviour of the systems: (i) the development of tensile stress acting as a negative pressure and (ii) the development of anisotropy which increases its importance deeper and deeper in the glassy state.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Effect of direct current sputtering power on the behavior of amorphous indium-gallium-zinc-oxide thin-film transistors under negative bias illumination stress: A combination of experimental analyses and device simulation
The effect of direct current sputtering power of indium-gallium-zinc-oxide (IGZO) on the performance and stability of the corresponding thin-film transistor devices was studied. The field effect mobility increases as the IGZO sputter power increases, at the expense of device reliability under negative bias illumination stress (NBIS). Device simulation based on the extracted sub-gap density of states indicates that the field effect mobility is improved as a result of the number of acceptor-like states decreasing. The degradation by NBIS is suggested to be induced by the formation of peroxides in IGZO rather than charge trapping.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Low temperature annealed amorphous indium gallium zinc oxide (a-IGZO) as a pH sensitive layer for applications in field effect based sensors
The use of a-IGZO instead of the conventional high-k dielectrics as a pH sensitive layer could lead to the simplification of fabrication steps of field effect based devices. In this work, the pH sensitivities of a-IGZO films directly deposited over a SiO{sub 2}/Si surface were studied utilizing electrolyte-insulator-semiconductor (EIS) structures. Annealing of the films was found to affect the sensitivity of the devices and the device with the film annealed at 400 {sup o}C in N{sub 2} ambience showed the better sensitivity, which reduced with further increase in the annealing temperature to 500 {sup o}C. The increased pH sensitivity with the film annealed at 400 {sup o}C in N{sub 2} gas was attributed to the enhanced lattice oxygen ions (based on the XPS data) and improved C-V characteristics, while the decrease in sensitivity at an increased annealing temperature of 500 {sup o}C was attributed to defects in the films as well as the induced traps at the IGZO/SiO{sub 2} interface based on the stretched accumulation and the peak in the inversion region of C-V curves. This study could help to develop a sensor where the material (a-IGZO here) used as the active layer in a thin film transistors (TFTs) possibly could also be used as the pH sensitive layer without affecting the TFT characteristics, and thus obviating the need of high-K dielectrics for sensitivity enhancement.
36 MATERIALS SCIENCE↗
Ultrafast defect dynamics: A new approach to all optical broadband switching employing amorphous selenium thin films
Optical switches offer higher switching speeds than electronics, however, in most cases utilizing the interband transitions of the active medium for switching. As a result, the signal suffers heavy losses. In this article, we demonstrate a simple and yet efficient ultrafast broadband all-optical switching on ps timescale in the sub-bandgap region of the a-Se thin film, where the intrinsic absorption is very weak. The optical switching is attributed to short-lived transient defects that form localized states in the bandgap and possess a large electron-phonon coupling. We model these processes through first principles simulation that are in agreement with the experiments.
36 MATERIALS SCIENCE↗
Phase selection and nanocrystallization in Cu-free soft magnetic FeSiNbB amorphous alloy upon rapid annealing
Nucleation of soft magnetic Fe{sub 3}Si nanocrystals in Cu-free Fe{sub 74.5}Si{sub 15.5}Nb{sub 3}B{sub 7} alloy, upon rapid (10 s) and conventional (30 min) annealing, was investigated using x-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy, and atom probe tomography. By employing rapid annealing, preferential nucleation of Fe{sub 3}Si nanocrystals was achieved, whereas otherwise there is simultaneous nucleation of both Fe{sub 3}Si and undesired Fe-B compound phases. Analysis revealed that the enhanced Nb diffusivity, achieved during rapid annealing, facilitates homogeneous nucleation of Fe{sub 3}Si nanocrystals while shifting the secondary Fe-B crystallization to higher temperatures resulting in pure soft magnetic nanocrystallization with very low coercivities of ∼10 A/m.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Density and glass forming ability in amorphous atomic alloys: The role of the particle softness
A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Unusual high B{sub s} for Fe-based amorphous powders produced by a gas-atomization technique
Fe-based alloy powders with a high Fe content of about 81 at.% were produced by a gas-atomization technique. Powders of Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} (at.%) alloy showed a good glass forming ability and exhibited unusual high saturation magnetic flux density of 1.57 T. The core-loss property at a frequency of 100 kHz for the compacted core made of the Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} powder is evaluated to be less than 500 kW/m{sup 3} under a maximum induction of 100 mT. Moreover, good DC-superposition characteristic of the core was also confirmed. These results suggest that the present Fe-based alloy powder is promising for low-loss magnetic-core materials and expected to contribute in miniaturization of electric parts in the near future.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Stiffening mechanisms in amorphous polyamide bio-nanocomposites
Dimer fatty acid polyamide nanocomposites based on flake- or needle-shaped nanoparticles were prepared via melt compounding. Transmission electron microscopy showed the presence of both individually dispersed particles and particle agglomerates in the polymer matrix. Dynamic mechanical analysis suggests that three stiffening mechanisms were operating. The reinforcing effect of the high stiffness inorganic filler particles is the primary contributor. Together with the chain confinement effect, that expresses itself in an apparent increase in the glass transition temperature, this provided an adequate rationalization of the stiffness variation below Tg. However, an additional stiffening effect is indicated at temperatures above Tg. The mechanism may involve dynamic network formation based on fluctuating hydrogen bonding interactions between the polymer chains and the filler particles.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Carrier collection losses in interface passivated amorphous silicon thin-film solar cells
In silicon thin-film solar cells the interface between the i- and p-layer is the most critical. In the case of back diffusion of photogenerated minority carriers to the i/p-interface, recombination occurs mainly on the defect states at the interface. To suppress this effect and to reduce recombination losses, hydrogen plasma treatment (HPT) is usually applied. As an alternative to using state of the art HPT we apply an argon plasma treatment (APT) before the p-layer deposition in n-i-p solar cells. To study the effect of APT, several investigations were applied to compare the results with HPT and no plasma treatment at the interface. Carrier collection losses in resulting solar cells were examined with spectral response measurements with and without bias voltage. To investigate single layers, surface photovoltage and X-ray photoelectron spectroscopy (XPS) measurements were conducted. The results with APT at the i/p-interface show a beneficial contribution to the carrier collection compared with HPT and no plasma treatment. Therefore, it can be concluded that APT reduces the recombination centers at the interface. Further, we demonstrate that carrier collection losses of thin-film solar cells are significantly lower with APT.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Structure of amorphous GeSe{sub 9} by neutron diffraction and first-principles molecular dynamics: Impact of trajectory sampling and size effects
The structure of glassy GeSe{sub 9} was investigated by combining neutron diffraction with density-functional-theory-based first-principles molecular dynamics. In the simulations, three different models of N = 260 atoms were prepared by sampling three independent temporal trajectories, and the glass structures were found to be substantially different from those obtained for models in which smaller numbers of atoms or more rapid quench rates were employed. In particular, the overall network structure is based on Se{sub n} chains that are cross-linked by Ge(Se{sub 4}){sub 1/2} tetrahedra, where the latter are predominantly corner as opposed to edge sharing. The occurrence of a substantial proportion of Ge–Se–Se connections does not support a model in which the material is phase separated into Se-rich and GeSe{sub 2}-rich domains. The appearance of a first-sharp diffraction peak in the Bhatia-Thornton concentration-concentration partial structure factor does, however, indicate a non-uniform distribution of the Ge-centered structural motifs on an intermediate length scale.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Ultrathin IBAD MgO films for epitaxial growth on amorphous substrates and sub-50 nm membranes
Not Available
36 MATERIALS SCIENCE↗