Understanding the physical origin of threshold switching and resistance drift phenomena is necessary for making a breakthrough in the performance of low-cost nanoscale technologies related to nonvolatile phase-change memories. Even though both phenomena of threshold switching and resistance drift are often attributed to localized states in the band gap, the distribution of defect states in amorphous phase-change materials (PCMs) has not received so far, the level of attention that it merits. This work presents an experimental study of defects in amorphous PCMs using modulated photocurrent experiments and photothermal deflection spectroscopy. This study of electrically switching alloys involving germanium (Ge), antimony (Sb) and tellurium (Te) such as amorphous germanium telluride (a-GeTe), a-Ge15Te85 and a-Ge2Sb2Te5 demonstrates that those compositions showing a high electrical threshold field also show a high defect density. This result supports a mechanism of recombination and field-induced generation driving threshold switching in amorphous chalcogenides. Furthermore, this work provides strong experimental evidence for complex trap kinetics during resistance drift. This work reports annihilation of deep states and an increase in shallow defect density accompanied by band gap widening in aged a-GeTe thin films.

The microstructure evolution and mechanical responses are investigated in uniaxial tensile test performed on AZ31 magnesium alloy sheets processed by the flat extrusion container. A novel emphasis based on the texture was used to estimate the relative magnitude of hardening effects related to the deformation twinning. The anisotropic behavior of the sheets is sensitive to the orientation of the crystals with respect to the loading direction. This is ascribed to the effect of the initial texture and the activation of their relative critical resolved shear stresses on slip and twinning. The increased accumulated hardening increases the twin nucleation stress. The deformation twinning significantly induces an asymmetry in the yield behavior. Moreover, it remarkably prolongs the slope of the stage II in the working hardening curve. An accepted notion is proposed that the preferential activity of deformation twinning exerts a significant effect on mechanical anisotropy during tension.

We have developed a reactive force field within the ReaxFF framework to accurately describe reactions involving aluminum–molybdenum alloy, which are part parameters of Al–O–Mo ternary system metastable intermolecular composites. The parameters are optimized from a training set, whose data come from density functional theory (DFT) calculations and experimental value, such as heat of formation, geometry data, and equation of states, which are reproduced well by ReaxFF. Body-centered cubic molybdenum’s surface energy, vacancy formation, and two transformational paths, Bain and trigonal paths are calculated to validate the ReaxFF ability describing the defects and deformations. Some structures’ elastic constant and phonon are calculated by DFT and ReaxFF to predict the structures’ mechanics and kinetic stability. All those results indicate that the fitted parameters can describe the energy difference of various structures under various circumstances and generally represent the diffusion property but cannot reproduce the elasticity and phonon spectra so well.

Grain boundary engineering (GBE) has been carried out in nickel-based Alloy 690 with different initial grain sizes. The microstructure evolution during GBE-processing is characterized using electron backscatter diffraction to study the initial grain size effects on the grain boundary network (GBN). The microstructures of the partially recrystallized samples revealed that the GBE-processing is a strain-recrystallization process, during which each grain-cluster is formed by “multiple twinning” starting from a single recrystallization nucleus. Taking into consideration the coincidence site lattices (CSLs) and ∑, which is defined as the reciprocal density of coincidence sites, a high proportion of low-∑ CSL grain boundaries (GBs) and large grain-clusters are found to be the features of GBE-processed GBN. The initial grain size has a combined effect on the low-∑ CSL GBs proportion. A large initial grain size reduces the number of recrystallization nuclei that form, increasing the cluster size, but decreasing twin boundary density. On the other hand, smaller initial grain sizes increase the density of twin boundary after recrystallization, while decreasing grain-cluster size. Neither the grain-cluster size nor the twin boundary density is the sole factor influencing the proportion of low-∑ CSL GBs. The ratio of the grain cluster size over the grain size governs the proportion of low-∑ CSL GBs.

The strain-rate sensitivity of ultrafine-grained aluminum (Al) and nanocrystalline nickel (Ni) is studied with an improved nanoindentation creep method. Using the dynamic contact stiffness thermal drift influences can be minimized and reliable creep data can be obtained from nanoindentation creep experiments even at enhanced temperatures and up to 10 h. For face-centered cubic (fcc) metals it was found that the creep behavior is strongly influenced by the microstructure, as nanocrystalline (nc) as well as ultrafine-grained (ufg) samples show lower stress exponents when compared with their coarse-grained (cg) counterparts. The indentation creep behavior resembles a power-law behavior with stress exponents n being ∼ 20 at room temperature. For higher temperatures the stress exponents of ufg-Al and nc-Ni decrease down to n ∼ 5. These locally determined stress exponents are similar to the macroscopic exponents, indicating that similar deformation mechanisms are acting during indentation and macroscopic deformation. Grain boundary sliding found around the residual indentations is related to the motion of unconstrained surface grains.

Ni–base alloy coatings were fabricated on 45 steel by laser cladding using a CW-CO2 laser system. The microstructure of the coatings was analyzed using optical microscope (OM), scanning electronic microscope (SEM), and x-ray diffractometer (XRD). The phase fractions, phase compositions, and solidification process in the coatings were calculated using Thermo-Calc software and compared with experimental results. The results show that a dense crack- and porous-free coating with good metallurgical bond is obtained under optimal process parameters. The coatings can be divided into three regions: clad zone (CZ), bonding zone, and heat-affected zone of the substrate. The CZ consists of γ-Ni, M7C3, CrB, and Ni3B phases. Based on the calculated results, the solidification process and reaction scheme in the coatings were discussed. The calculated results obtained from Thermo-Calc software agree with the experimental data well. It is beneficial to the coating design for a desirable microstructure and mechanical properties.

Sn–40 at.% Mn peritectic alloys were directionally solidified at different growth rates (1–100 μm/s) under a steep temperature gradient (40 K/mm). The migration of secondary dendrite arm was observed in this peritectic alloy in which both the primary phase and the peritectic phase are intermetallic compounds with nil solubility. This migration is caused by coupling remelting/solidification at the hot/cold sides of the liquid pool between two adjacent secondary dendrite arms by temperature gradient zone melting. Its novel feature is that the remelting temperature of primary phase is a little higher than the solidification temperature of peritectic phase. Analytical solutions based on the assumption that the solubility of both primary and peritectic phases are nil have been proposed to describe this migration. It has also been found that the migration of secondary dendrite arm is most obvious at intermediate growth rates under steep temperature gradient in the directionally solidified Sn–40 at.% Mn peritectic alloy.

The ternary Cu–Co–Fe alloy was rapidly solidified by using the high pressure gas atomization technique. Powders with a well-dispersed microstructure resulting from the liquid–liquid phase transformation were obtained. A model describing the microstructure evolution in an atomized drop during the liquid–liquid phase transformation was developed. The kinetic details of the liquid–liquid phase transformation were discussed. The numerical results show a favorable agreement with the experimental ones. They demonstrate that under the rapid cooling conditions of gas atomization, the spatial phase separation due to the Marangoni migration of the minority phase droplets is very weak. Also, the effect of Ostwald coarsening of the minority phase droplets on the microstructure is negligible. For Cu-10 wt% Co-10 wt% Fe alloy, the average radius and number density of the Fe–Co-rich particles depend exponentially on the cooling rate of the melt during the nucleation period of the Fe–Co-rich droplets.

The hardness changes caused by formation of the metastable and stable phases were examined and correlated with the microstructural changes in grain interior and grain boundary during aging at 350 °C to clarify the age-hardening and softening mechanism of a low-gold Au-Cu-Ag-Pd dental alloy. Aging in this context refers to the time-delay that occurs wherein such alloys are kept at elevated temperatures for periods upto many hours to allow precipitation or ordering to take place. During the period of increasing hardness, the matrix was separated into the Ag-rich α1 and AuCu I phases through the metastable phases, forming block-like structure. The apparent hardening was attributed primarily to lattice strain due to the tetragonality of AuCu I′ [the primer (′) here indicates a metastable phase; likewise (I) and (I′) indicate stable AuCu I and metastable AuCu I′ phases, respectively] and AuCu I phases along the c-axis, secondarily to the coherency or semicoherency strain between the metastable α1′ and AuCu I′ phases and between the α0 and AuCu I phases along the a-axis. The apparent softening was caused primarily by growth and coarsening of the lamellar structure in the grain boundaries, secondarily by coarsening of the block-like structure in the grain interior.

A quasicrystal (QC)- based alloy composite was made by copper mold casting under a low-vacuum level condition at the bulk metallic glass (BMG)- forming composition (Zr65Cu15Al10Ni10)90Nb10. The QC alloy consisted of a majority of icosahedral quasicrystal phase and a small amount Zr-rich glassy phase. Under uniaxial compression at room temperature, the BMG alloy exhibits a certain plastic strain; the QC alloy is much stronger but brittle. The icosahedral glass model was used to describe the I-phase structure. The structure–property relations of the BMG and QC alloys are discussed assuming the common preferential icosahedral atomic structure in both cases and the existence of local glue structure in the BMG structure.

A kinetic model of crystallization based on two-dimensional nucleation and growth of plate-like crystals with constant thickness is analyzed. It is shown that plate thickness required for nucleation is limited. The lower limit is determined by zero Gibbs’ free energy of transition, the upper one corresponds to the conditions when the critical cluster volume of nucleation is equal to two elementary kinetic units. Effects of plate thickness on crystallization kinetics are discussed. In the lower temperature range, creation of thicker plates is preferred. For a given plate thickness, frequency of the phase transition decreases with increasing temperature. Numerical calculations for α-polypropylene concern kinetics of primary nucleation and global phase transition in a system of one or several fractions of plate-like kinetic elements.

InN films have been grown on sapphire substrates nitrided by N plasma with different durations by radio-frequency plasma assisted molecular beam epitaxy (RF-MBE). In-depth investigation reveals that AlN is generated on a sapphire surface during the nitridation, and 60 min nitridation helps in the formation of an ordered and flat AlN interlayer between the substrate and the InN film, which improves the surface migration of In atoms on the substrate, and consequently helps in obtaining a single-crystalline c-plane InN film of high quality with 1.0 × 1019 cm−3 carrier density and 1350 cm2/(V·s) carrier mobility. Too short nitridation duration will result in a polycrystalline InN film, and too long nitridation duration will damage the surface quality of the newly generated AlN interlayer which consequently deteriorates the InN film quality. Control of the AlN interlayer quality plays a critical role in the growth of a high-quality InN epitaxial film on the sapphire substrate.

A simple and modified solvothermal method using oxalate precursor, used to synthesize Cd1−xNixO (x = 0.047, 0.102, and 0.163) nanoparticles and their phase structure, morphology, optical and magnetic properties, have been investigated. X-ray diffraction studies revealed that as-prepared Ni-doped CdO solid solutions are highly crystalline and stabilized in a monophasic cubic CdO structure. X-ray diffraction and ICP-MS studies confirmed the incorporation of Ni2+ in a CdO matrix. The average grain size was found to be 30, 15, and 11 nm, respectively, using transmission electron microscopic studies. High surface area in the range of 118–143 m2/g has been achieved for these solid solutions using the multipoint BET method, which increases on increasing Ni concentration in Cd lattice site. The optical band gap of these solid solutions shows red shift to the undoped CdO. Ni-doped CdO nanoparticles exhibit co-existence of paramagnetism and ferromagnetism.

A rapid low-pressure plasma sintering process of inkjet-printed silver nanoparticles is reported, yielding a conductivity of 11.4% of bulk silver within 1 min of plasma exposure and a final conductivity up to 40% of bulk silver for longer sintering times. The maximum processing temperature did not exceed 70 °C, which enabled the use of cost-effective polyethylene terephthalate (PET) foils. Fully functional radio-frequency identification (RFID) tags were prepared with inkjet-printed antennas, which showed similar results as screen-printed devices. The inkjet-printed antennas require significantly less materials, hence thinner layers, than the screen-printed references.

Optimization of the pore topology in organosilicate glass (OSG) is crucial in the development of dielectrics with an extremely low k-value and a relatively high Young’s modulus. In this paper, a finite-element modeling strategy is applied to develop a general understanding of the relationship between porosity, pore topology, and elastic modulus for the porous OSG thin films. This relationship in combination with the experimental elastic modulus data from nanoindentation (NI) studies is used to predict the pore structure of various OSG films. In addition, positron annihilation spectroscopy measurements are performed to determine the threshold porosity for the transition from nonoverlapping to overlapping porous structure. A similar threshold value is determined based on the finite-element modeling and experimental NI data.

The quality of interface between ultrathin silicon dioxide films and their silicon (Si) wafers was characterized using room-temperature photoluminescence (RTPL) and Raman spectroscopy. Three types of low-temperature (350 °C or room temperature) oxide films on Si grown by different techniques were measured and compared with Si wafers having native oxide and high-temperature thermally grown oxide films. Significant RTPL spectra and intensity variations were measured among low-temperature oxide films. Very strong excitation wave length dependence of RTPL spectra and intensity was observed from the low-temperature oxide films on Si whereas the RTPL spectra and intensity from Si with native oxide and thermally grown oxide films were consistent. Stress in the Si lattice, with different low-temperature oxide layers, showed noticeable differences depending on the oxidation technique used. Key device performance parameters of image sensor devices fabricated using three different low-temperature oxide films showed good correlation with the RTPL and Raman measurement results. The RTPL spectra and Raman shifts are very sensitive to the quality of the oxide/Si interface and can be used as an interface quality monitoring technique.