70 research outputs found
Modeling of radiative - conductive heat transfer in compositing materials
A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity
On Properties of Boundaries and Electron Conductivity in Mesoscopic Polycrystalline Silicon Films for Memory Devices
We present the results of molecular dynamics modeling on the structural
properties of grain boundaries (GB) in thin polycrystalline films. The
transition from crystalline boundaries with low mismatch angle to amorphous
boundaries is investigated. It is shown that the structures of the GBs satisfy
a thermodynamical criterion. The potential energy of silicon atoms is closely
related with a geometrical quantity -- tetragonality of their coordination with
their nearest neighbors. A crossover of the length of localization is observed.
To analyze the crossover of the length of localization of the single-electron
states and properties of conductance of the thin polycrystalline film at low
temperature, we use a two-dimensional Anderson localization model, with the
random one-site electron charging energy for a single grain (dot), random
non-diagonal matrix elements, and random number of connections between the
neighboring grains. The results on the crossover behavior of localization
length of the single-electron states and characteristic properties of
conductance are presented in the region of parameters where the transition from
an insulator to a conductor regimes takes place.Comment: 8 pages, 3 figure
Modeling of radiative - conductive heat transfer in compositing materials
A layer of composite material is investigated, which is heated one-sidedly with one-dimensional energy transfer accounting for thermal conductivity and radiation. A mathematical model is suggested for non-stationary coefficient thermophysical problem under radiative-conductive heat transfer in a material layer. Temperature dependencies of thermal capacity and thermal conductivity coefficient of composite radio-transparent material have been determined through numerical modeling by solving the coefficient reverse problem of thermal conductivity
Dynamics of combined electron beam and laser dispersion of polymers in vacuum
The mechanisms of the impact of the laser assisting effect on the dispersion kinetics and on the structure of the deposited layers in electron beam dispersion of a polymer target were analyzed. The proposed model and analytical expressions adequately describe the kinetic dependence of the polymer materials dispersion rate in a vacuum on the intensity of laser processing of their dispersion zone
Properties of cage rearrangements observed near the colloidal glass transition
We use confocal microscopy to study the motions of particles in concentrated
colloidal systems. Near the glass transition, diffusive motion is inhibited, as
particles spend time trapped in transient ``cages'' formed by neighboring
particles. We measure the cage sizes and lifetimes, which respectively shrink
and grow as the glass transition approaches. Cage rearrangements are more
prevalent in regions with lower local concentrations and higher disorder.
Neighboring rearranging particles typically move in parallel directions,
although a nontrivial fraction move in anti-parallel directions, usually from
pairs of particles with initial separations corresponding to the local maxima
and minima of the pair correlation function , respectively.Comment: 5 pages, 4 figures; text & figures revised in v
Ion-beam sputtering of NiO hole transporting layers for p-i-n halide perovskite solar cells
Ion-beam sputtering offers significant benefits in terms of deposition
uniformity and pinhole-free thin-films without limiting the scalability of the
process. In this work, the reactive ion-beam sputtering of nickel oxide has
been developed for the hole transporting layer of a p-i-n perovskite solar
cells (PCSs). The process is carried out by oxidation of the scattered Ni
particles with additional post-treatment annealing regimes. Using deposition
rate of 1.2 nm/min allowed growth of very uniform NiO coating with the
roughness below 0.5 nm on polished Si wafer (15x15 cm2). We performed a complex
investigation of structural, optical, surface and electrical properties of the
NiO thin-films. The post-treatment annealing (150-300C) was considered as an
essential process for improvement of the optical transparency, decrease of
defects concentration and gain of the charge carrier mobility. As result, the
annealed ion-beam sputtered NiO films delivered a power conversion efficiency
(PCE) up to 20.14%, while device without post-treatment reached the value of
11.84%. The improvement of the output performance originated from an increase
of the short-circuit current density (Jsc), open circuit voltage (Voc), shunt
and contact properties in the devices. We also demonstrate that the ion-beam
sputtering of NiO can be successfully implemented for the fabrication of large
area modules (54.5 cm2) and PSCs on a flexible plastic substrate (125 microns)
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