Applied Physics A Solids and Surfaces

Crystallographic models of TiZrVMo HEAs were established here for six distinct grain sizes ranging from 7.4 to 23.5 nm. A consistent rise in tensile stress maxima is observed with diminishing grain size. Remarkably, the TiZrVMo composition demonstrates its optimal performance at a grain size of 12.4 nm. During tensile processes, TiZrVMo displays pronounced atomic plane slip and an increase in intra-grain dislocations, indicating significant plastic deformation. Conversely, TiZrV3Mo exhibits limited slip and localized stress, signifying a lower degree of plasticity. This research unveils the intricate interplay of grain boundary phenomena, dislocation behavior, and atomic plane slip, thereby shedding light on the mechanical properties of HEAs.

We design a back-illuminated p–i–n–i–n separate absorption and multiplication (SAM) AlGaN solar-blind avalanche photodiode (APD) with a low Al-content p-graded AlxGa1-xN layer and a high/low Al-content AlGaN multiplication layer. Simultaneously, an III-nitride AlN/Al0.64Ga0.36 N distributed Bragg reflector (DBR) structure is inserted to improve the solar-blind photoresponse for the designed APD. The simulation results show that the designed APD exhibits enhanced optoelectronic characteristics compared to the conventional APD, which is attributed to the higher holes impact ionization coefficient and generated polarization electric field in the same direction as the applied bias field of the designed APD. The designed APD exhibits significant enhanced avalanche gain and reduced avalanche breakdown voltage compared with the conventional APD.

A new tubular hot-wire chemical vapor deposition (HWCVD) system using a tubular quartz vacuum chamber has been fabricated. The filaments in this system can heat the substrate and act as a gas activator and thermally activator for gas species at the same time. The nano- and microcrystalline diamond coatings on the surface of steel AISI 316 substrates have been grown. To assess the results, SEM and FESEM images and Raman spectroscopy investigations have been applied. The results reveal that micro- and nanocrystalline diamond structures have been formed in the coatings, but the disordered diamond and some non-diamond phases, such as graphitic carbons, are also present in the coating layers. The analytical measurements show the growth of diamond films with well-faceted crystals in (111) direction. However, intrinsic stress, secondary nucleation, and poor adhesion are the main issues of future research for this new designed HWCVD.

The crystal structure and orientation of As precipitates in annealed low-temperature GaAs (LT-GaAs) layers have been investigated by transmission electron microscopy. Three types of As precipitates were identified in layers grown by molecular beam epitaxy at substrate temperatures from 180° to 210° C. In the monocrystalline LT-GaAs layers small “pseudocubic” As precipitates (2–3 nm diameter) coherent with the GaAs lattice were observed. These precipitates lose their coherency when a certain critical size is exceeded. Precipitates of similar sizes are occasionally found for which a TEM lattice image cannot be obtained. These precipitates are believed to be amorphous. Larger As precipitates with a hexagonal structure (>4 nm diameter) were also found in the layers. These hexagonal As precipitates were observed to be largest near structural defects. The effect of these precipitates on the structure and on the electronic properties of the host GaAs is discussed.

Tight focusing of a sub-picosecond laser pulse in a transparent dielectric provides a mean for localized deposition and plasma formation. A micro-explosion in a confined geometry results in a sub-micron cavity formation. Our numerical simulations show the cavity size is strongly dependent on the parameters of the equation of state such as the Grüneisen coefficient or the latent heat of sublimation. A comparison of numerical simulations with experimental data should allow a tuning of equations of state in the domain of extreme parameters

Empirical equations of state (EoSs) are developed for solids, applicable over extended temperature and pressure ranges. The EoSs are modeled as multiply broken power laws, in closed form without the use of ascending series expansions; their general analytic structure is explained and specific examples are studied. The caloric EoS is put to test with two carbon allotropes, diamond and graphite, as well as vitreous silica. To this end, least-squares fits of broken power-law densities are performed to heat capacity data covering several logarithmic decades in temperature, the high- and low-temperature regimes and especially the intermediate temperature range where the Debye theory is of limited accuracy. The analytic fits of the heat capacities are then temperature integrated to obtain the entropy and caloric EoS, i.e. the internal energy. Multiply broken power laws are also employed to model the isothermal EoSs of metals (Al, Cu, Mo, Ta, Au, W, Pt) at ambient temperature, over a pressure range up to several hundred GPa. In the case of copper, the empirical pressure range is extended into the TPa interval with data points from DFT calculations. For each metal, the parameters defining the isothermal EoS (i.e. the density–pressure relation) are inferred by nonlinear regression. The analytic pressure dependence of the compression modulus of each metal is obtained as well, over the full data range.

In the history of metal–oxide–semiconductor field effect transistor (MOSFET), the quality of its gate oxide has been a cornerstone of the present semiconductor integrated circuits. The changes of gate dielectrics from conventional SiO2 gate oxide into high-k materials has brought us more challenges in various aspects of transistors, especially the reliability improvement when MOSFET dimension is continually scaled. Depending on the making of high-quality gate dielectrics, it plays a major role for the manufacture of high-end CPU with ultra-low power and low leakage, nowadays. There are two major well-known breakdowns in MOSFET’s history. Not until 2015, a world first observation of the breakdown, different from soft and hard breakdown, named dielectric fuse breakdown, dFuse, was discovered, as a result of CMOS technology moving into the high-k metal-gate (HKMG) era. In this paper, we will introduce from the inception of the Ig-RTN (random telegraph noise) measurement on the understanding of breakdown in 2008 and briefly describe the fundamentals of the RTN technique. Later in 2015, a version 2.0 of this Ig-RTN measurement, named Ig-transient, was successfully developed to delineate the breakdown path in HKMG transistors, from which a third breakdown, named dielectric fuse breakdown, was discovered. Its origin and physical mechanism have been discussed. This breakdown relies on the understanding of a leakage path in the gate dielectric of MOSFET, especially the movement of oxygen ions and the oxygen vacancies in the gate dielectric. Sophisticated measurement technique has also been developed to identify the traps generated in the gate dielectrics which laid the foundations on the understanding of trap generation as a function of time. In the end, two major applications in memories are presented, one is in the use of one-time-programming memory and the other on the understanding of the switching phenomena involved in the operation of resistance random-access memory (RRAM).

Ho–substituted Bi4-xHoxTi2FeO12 (x = 0, 0.5, 1.0, 1.5) n = 3 Aurivillius layered perovskite compounds were prepared by a conventional solid-state reaction method. X-ray diffraction study reveals that the compounds exhibited a major orthorhombic structure with the B2cb space group. A plate-like grain with high randomness in the distribution of Ho-modified BTFO compounds was noticed in the SEM studies. T—dependent dielectric studies were performed to examine the role of defect dipole orientation and oxygen vacancies on dielectric relaxation. For x > 0.50 compositions, a decrease in Curie temperature (Tm) with the increase in Ho-substituted in BTFO ceramics was observed. A temperature-dependent AC conductivity study reveals that the ionic conductivity induced by doubly ionized oxygen vacancies is prominent in the high-temperature region. An Increase in polarization values was observed with Ho doping due to improved grain boundaries. The detailed studies on the ferroelectric (P-E) loops and magnetization (M-H) loops of Ho—substituted BTFO ceramics were determined to point out the inherent multiferroic character. The basic photoluminescence (PL) studies indicated a well noticed two distinct bands in the visible region along with a weak PL band observed in the infra-red (IR) region, which suggests the emission involves the two types of Ho3+ centers for the visible bands.

For the first time, chromium substituted calcium hexaferrite (CaCr $$_{x}$$ Fe $$_{12-x}$$ O $$_{19}$$ (x = 0,2,4,6 and 8)) nanoparticles (NPs) are synthesized by Musaparadisiaca (banana) peel extract mediated solution combustion method followed by calcination at 500 $$^{o}$$ C. The Bragg reflections confirms the formation of M-type hexaferrite with P6 $$_{3/mmc}$$ space group. No other impurity peaks are observed, except the variation in intensity and width of the peaks. The surface morphology consists irregular shaped NPs. Agglomeration of NPs was found to be maximum at CaCr $$_{x}$$ Fe $$_{12-x}$$ O $$_{19}$$ (x = 8). The optical energy band gap was calculated using Wood and Tauc’s relation which found to be in the range 3.31 to 2.92 eV. The energy band gap decreases whereas the crystallite size increases with increase in chromium substitution. The radiation shielding parameter- mass attenuation coefficient is measured and its derivatives such as mean free path, half value layer, effective atomic number, electron density, energy absorbing building factor variation at different energy region are discussed in detail along with neutron shielding and Bremsstrahlung radiation parameters with respect to chromium concentration in calcium hexaferrite NPs. These parameters plays an important role in radiation dosimetry.