We determine the nonequilibrium grain size distribution (GSD) during the crystallization of a solid in d-dimensions under fixed thermodynamic conditions, for the random nucleation and growth model, and in the absence of grain coalescence. Two distinct generalizations of the theory established earlier are considered. A closed analytic expression of the GSD useful for experimental studies is derived for anisotropic growth rates. The main difference from the isotropic growth case is the appearance of a constant prefactor in the distribution. The second generalization considers a Gaussian source term: nuclei are stable when their volume is within a finite range determined by the thermodynamics of the crystallization process. The numerical results show that this generalization does not change the qualitative picture of our previous study. The generalization only affects quantitatively the early stage of crystallization when nucleation is dominant. The remarkable result of these major generalizations is that the nonequilibrium GSD is robust against anisotropic growth of grains and fluctuations of nuclei sizes.

In the semiconductor industry, ion implantation and the subsequent annealing have ubiquitously been used to mitigate residual stresses and crystallographic defects in a film-on-substrate system. However, the relationship between crystal quality and residual stresses induced by lattice mismatch and disparate thermal expansions has not yet been understood. This paper aims to clarify the mist through an in-depth investigation into the stress and microstructure variations in the ion implantation and annealing processes. It was found that a higher-energy implantation with a higher ion dose density leads to a more significant relief of residual stresses. However, a higher annealing temperature, which results in fewer defects, will bring about greater residual stress regeneration. To achieve a higher crystal quality but lower stresses, it is necessary to enable the ions to penetrate through the film to cause substrate expansion, such that the mismatch between the film and substrate is mitigated and the high temperature annealing can be utilized to minimize the interface defects.

We investigate the orientation transition and strain relaxation in oxygenated epitaxial strontium-doped lanthanum nickelate, La1.875Sr0.125NiO4+δ (LSNO) thin films grown on single crystal strontium titanate, SrTiO3 (STO) substrates. Structural evolution has been studied as a function of film thickness by x-ray diffraction, pole figure analysis, and transmission electron microscopy (TEM). The LSNO layer grows epitaxial (OR1) with respect to the STO substrate with an orientation (001)OR1//(001)STO and <001>OR1//<001>STO. This orientation is maintained up to approximately 15 nm as observed from TEM, at which point it undergoes reorientation and lattice mismatch strain relaxation. The growth continues with a new orientation (OR2) as (100)OR2//(001)OR1 and with <100>OR2//<001>OR1 and <001>OR2//<001>OR1 with respect to the epitaxial LSNO layer. We consider possible mechanisms in detail leading to these phenomena given that the potassium nickel fluoride (K2NiF4)-structured lattice is able to accommodate excess oxygen interstitials and corresponding changes in the Ni valence state. By investigating the phase space of deposition parameters, we experimentally identify key factors leading to the reorientation phenomena.

Multilayer Si/Ge heterostructures with the thickness of Ge layers varying from 2 to 12 monolayers (MLs) were formed by molecular beam epitaxy on the (001) Si substrates at 300 °C (Ge) and 450 °C (Si). Using conventional and aberration corrected scanning transmission electron microscopy, x-ray reflectometry and x-ray standing waves, a thorough study of the Si/Ge heterostructures was performed. Optical properties of the heterostructures were probed by photoluminescence spectroscopy. It is shown that the growth of Ge layers up to a thickness of 5 ML occurs through the Frank–van der Merwe mechanism. For thicker Ge layers the growth mechanism of the Si–Ge heterostructure changes to Stranski–Krastanov with Si–Ge islands having the shape of inverted pyramids. We discuss the intermixing of Si and Ge due to stress induced interdiffusion. An explanation of the influence of the observed structural peculiarities on the PL spectra of the heterostructures is given.

A high open-circuit voltage (VOC) of an organic photovoltaic device (OPV) has been realized using an ultrathin electron donor layer, 2,3-Bis(2-(diphenylamino)-9,9′- spirobifluorene-7-yl)fumaronitrile (PhSPFN), which exhibits the most suitable and low-lying highest occupied molecular orbital (HOMO) to align between the anode and donor energy levels. The planar heterojunction OPV, represented as indium tin oxide electrode/PhSPFN/fullerene C60/bathocuproine/aluminum electrode shows high performance with a VOC of 0.91 V, short current density of 3.9 mA/cm2, fill factor of 56% and power conversion efficiency of 2% under an air-mass of 1.5 global illumination at 1 sun. In addition, the effect of the VOC change is discussed in terms of various donor materials. The VOC turns out to be restricted to the energetic alignment between the work function of the anode and the HOMO level, indicating that the optimization of VOC requires energetically good contact between the anode and organic materials.

Alternating layer-by-layer (LbL) deposition of polycations and polyanions on porous substrates is a convenient and versatile method for forming high-flux nanofiltration (NF) membranes. In this work, positively charged NF membranes were fabricated by the LbL assembly of poly(ethyleneimine) (PEI) and poly(sodium 4-styrenesulfonate) (PSS) on the modified polyacrylonitrile ultra-filtration substrate. The charge variation with each layer was characterized by zeta potential. ATR-FTIR, SEM, N2 adsorption and the weight changes with bi-layers were used to confirm the LbL deposition of the polyelectrolytes. NF performances of the prepared membrane with a number of bi-layers as well as solute concentrations were also investigated. The results of zeta potential showed that the whole multilayer films exhibited periodic variations in positive charge. NF results indicated that the rejection of Ni2+ and Cd2+ ions increased, while the permeate fluxes decreased with the number of bi-layers. And the rejections of the metal ion solutes were 98.02% for CuSO4, 95.53% for ZnSO4, 95.66% for NiCl2, 94.9% for CdCl2, along with permeation fluxes of 19.02, 19.72, 24.02, and 21.19 L/m2·h, respectively.

A new type of cross-linked poly(vinyl alcohol) (PVA)-sulfosuccinic acid (SSA) polymers were synthesized by varying the amount of SSA and then blending with 3-amino-1,2,4-triazole (ATri) and 1H-1,2,4-triazole (Tri) at different stoichiometric ratios to obtain proton conductive membranes in anhydrous state. The proton conductivities of membranes were investigated as a function of azole composition, SSA composition, and operating temperature. The final structures of the copolymers were confirmed by Fourier transform infrared spectra. The resultant hybrid membranes are transparent, flexible, and showed good thermal stability up to approximately 200 °C. Differential scanning calorimetry results illustrated the homogeneity of the materials. The cross-linking of the structure was confirmed by the alteration of solubility of the membranes. Methanol permeability measurements showed that the composite membranes have lower methanol permeability compared to Nafion 112. The proton conductivity of the membranes continuously increased with increasing SO3H content and 3-amino-1,2,4-triazole (ATri) content. A maximum proton conductivity of 7.26 × 10−3 S/cm was achieved for ATri-3 at 140 °C under anhydrous conditions. Incorporation of ATri unit (according to Tri unit) significantly increased the proton conductivity of the membranes, probably due to the ion transport channel or network structures formed in the membranes.

We investigate the size-dependent carrier dynamics and activation energy in cadmium telluride/zinc telluride (CdTe/ZnTe) quantum dots (QDs) grown on silicon (Si) substrates. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to the ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy level with increasing CdTe thickness, owing to an increase in the size of the CdTe QDs. Time-resolved PL measurements performed to study the carrier dynamics reveal a longer exciton lifetime for CdTe/ZnTe QDs with increasing CdTe thickness on account of the reduction of the exciton oscillator strength resulting from a strong built-in electric field in the larger QDs. The activation energy of the electrons confined in the CdTe/ZnTe QDs, as obtained from the temperature-dependent PL spectra, increases with increasing CdTe thickness. These results indicate that the carrier dynamics and activation energy of CdTe/ZnTe QDs are affected by the size of the CdTe QDs.

In this work, we report on the optoelectronic and photocatalytic features of europium (Eu3+)-doped TiO2 nanoscale particles synthesized via a sol-gel mediated rapid-condensation technique. X-ray diffraction studies have revealed the mixed phases of the synthesized systems. In particular, a mixture of anatase, brookite, and rutile phases was found to coexist beyond a sintering temperature of 600 °C while a pure anatase phase was witnessed below 500 °C. The photoluminescence spectra of ∼7 nm sized anatase TiO2 nanoparticles have exhibited different intra 4f (Eu3+ ion related) transitions with the most intense red emission (5D0→7F2) peak located at ∼613 nm. The emissions due to color centers and oxygen vacancies of TiO2 were also evident in the PL spectra. The Brunauer-Emmett-Teller surface area analysis has revealed a significant increment of surface area and pore volume owing to the enhanced interfacial region introduced by point defects and dislocations due to Eu doping. The photocatalytic activity of the Eu3+ doped TiO2 nanoscale system was found to be ∼12% stronger than its un-doped counterpart, as assessed from the degradation of methyl orange (MO) solution under UV light irradiation. The percentage of degradation was found to be strongly dependent on the duration of the UV exposure and Eu doping concentration. As an efficient photosensitive candidate, rare earth sensitized TiO2 systems would bring new insights while displaying both optoelectronic and photocatalytic characteristics through use of the localized states present in the band gap of the host.

Er3+-doped oxyfluoride transparent glass and glass-ceramics (GCs) containing SrF2 nanocrystals were prepared and their spectroscopic properties were investigated. The formation of SrF2 nanocrystals in GCs has been confirmed by x-ray diffraction (XRD) and transmission electron microscopy. The Judd-Ofelt (JO) parameters have been evaluated from absorption spectra of the Er3+-doped glass and GCs, which are used to predict radiative properties for some important luminescence levels of Er3+ ions in glass and GCs. The XRD and JO parameters suggest that the Er3+ ions are progressively incorporated into the SrF2 nanocrystals in the GCs compared with glass. The up-conversion luminescence intensity increases significantly in GCs with increase in time of thermal treatment. The lifetime of the 4S3/2 level of the Er3+ ions in GCs is found to be slightly higher than that in the glass due to the incorporation of Er3+ ions into the lower phonon energy of SrF2 nanocrystals in the GCs.

The use of MgO nanoparticle (NP) loaded poly(methylsilsesquioxane) (PMSQ) as a low temperature processable composite dielectric has been investigated. The composite dielectrics have been synthesized using facile ultrasonic mixing of trimethoxymethylsilane (MTS), butanol (n-BuOH) and deionized water at 60 °C, with MgO loadings from 0.096 up to 0.39 wt% of the initial solution. Thin films of the composite materials produced have shown an increase in dielectric constant from 2.8 for raw PMSQ up to 3.4 for the 0.39 wt% loaded PMSQ + MgO NP composites at frequencies up to 2 MHz, comparable to 3.9 for SiO2. The composite dielectric materials have shown suitability as a dielectric material for a P3HT OFET, with the performance comparable to a standard SiO2 dielectric control sample.

In this work, the morphology of BiFeO3 was successfully modulated from microsphere to microcube by using a polyanion, poly (methyl vinyl ether-alt-maleic acid) (PMVEMA), in a microwave assisted hydrothermal route. A simple ultrasonic purification method has been developed to obtain pure phase BiFeO3 from the crude products without using any chemicals. X-ray diffraction results confirmed the capability of this purification method. When increasing the amount of PMVEMA, the morphology of BiFeO3 gradually changed from microsphere to microcube as illustrated by scanning electron microscopy. A mechanism was suggested for the morphology evolution of BiFeO3. After the formation of the small BiFeO3 single crystal, PMVEMA preferentially absorbed on one side of the crystals through specific and/or noncovalent interactions, resulting in the preferential integration of these crystals to form microcubes. The magnetic properties of these microcrystals were also investigated and the magnetization of the microcubes increased with the decrease of temperature.

The porous Li1.2Ni0.13Co0.13Mn0.54O2 nanoplate is prepared by colloidal crystal template assembled by the poly (methyl methacrylate) (PMMA) beads. Scanning electron microscopy and transmission electron microscopy results show that the nanoplates of porous solid solution cathodes are composed of nanoparticles with a size range of 30 nm, which interweave together forming an open porous structure. Electrochemical tests show that porous Li1.2Ni0.13Co0.13Mn0.54O2 cathode could deliver higher discharge capacity than that of bulk Li1.2Ni0.13Co0.13Mn0.54O2 cathode at all C-rates. The enhanced structural stability reflected by high ratios of integrated Intensity I(003)/I(104) and lattice parameters c/a, high specific surface area, a fast reaction and ionic diffusion kinetics of the nanoplates are considered attributable to the improved electrochemical properties.

A novel and simple method for gelcasting of alumina was developed using a nontoxic and water-soluble copolymer of isobutylene and maleic anhydride (commercially called Isobam). In this method, there is requirement of only a small amount of Isobam (0.3 wt%) and neither initiators nor dispersants are needed for preparation and gelation of a 50 vol% solids loaded alumina slurry. The gelation rate increased with increasing solids loading but decreased with increasing Isobam content. A typical gelation time was 38 min for the slurry containing 50 vol% solids loading and 0.3 wt% Isobam. The resultant wet gel was strong enough to allow reversible bending and twisting. This simple gelling system is attractive for wet forming of ceramics because only a single additive, which acts as both dispersant and gelling agent at room temperature in air, is used.

The present work demonstrates the synthesis of Cu–10 wt% TiB2 composites with a theoretical density of more than 90% by tailoring the spark plasma sintering (SPS) conditions in the temperature range of 400–700 °C. Interestingly, 10 wt% Pb addition to Cu–10 wt% TiB2 lowers the sinter density and the difference in the densification behavior of the investigated compositions was discussed in reference to the current profile recorded during a SPS cycle. The sintering kinetics and phase assemblage were also discussed in reference to surface melting of the constituents prior to bulk melting temperature, temperature dependent wettability of Pb on Cu, diffusion kinetics of Cu as well as the formation of various oxides. An important result is that a high hardness of around 2 GPa and relative density close to 92% ρtheoretical was achieved for the Cu–10 wt% TiB2–10 wt% Pb composite, and such a combination has never been achieved before using any conventional processing route.

A kinetics model for the precipitation of M23C6 in high Cr ferritic heat resistant steel during tempering has been developed assuming the site-saturated nucleation, carbon diffusion-controlled growth and soft-impingement. The growth coefficient in this model is temperature-dependent, and the Arrhenius equation is applied to describe the growth coefficient, in which the growth activation energy is nearly equal to the diffusion activation energy of carbon in martensite. The effect of main parameters in this model has been discussed in detail. By this model, the precipitation of M23C6 during tempering can be predicted accurately in the case of 2D, and a good agreement with experimental data in previous work has been achieved.