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The wide variety of silicon materials used by various groups to investigate LeTID make it difficult to directly compare the defect concentrations (N t) using the typical normalised defect density (NDD) metric. Here, we propose a new formulation for a relative defect concentration (β) as a correction for NDD that allows flexibility to perform lifetime analysis at arbitrary injection levels (Δn), away from the required ratio between Δn and the background doping density (N dop) for NDD of Δn/N dop = 0.1. As such, β allows for a meaningful comparison of the maximum degradation extent between different samples in different studies and also gives a more accurate representative value to estimate the defect concentration. It also allows an extraction at the cross-over point in the undesirable presence of iron or flexibility to reduce the impact of modulation in surface passivation. Although the accurate determination of β at a given Δn requires knowledge of the capture cross-section ratio (k), the injection-independent property of the β formulation allows a self-consistent determination of k. Experimental verification is also demonstrated for boron-oxygen related defects and LeTID defects, yielding k-values of 10.6 ± 3.2 and 30.7 ± 4.0, respectively, which are within the ranges reported in the literature. With this, when extracting the defect density at different Δn ranging between 1014 cm−3 to 1015 cm−3 with N dop = 9.1 × 1015 cm−3, the error is less than 12% using β, allowing for a greatly improved understanding of the defect concentration in a material.

GaTe is a two-dimensional III–VI semiconductor with suitable direct bandgap of ∼ 1.65 eV and high photoresponsivity, which makes it a promising candidate for optoelectronic applications. GaTe exists in two crystalline phases: monoclinic (m-GaTe, with space group C2/m) and hexagonal (h-GaTe, with space group P63/mmc). The phase transition between the two phases was reported under temperature-varying conditions, such as annealing, laser irradiation, etc. The explicit phase transition temperature and energy barrier during the temperature-induced phase transition have not been explored. In this work, we present a comprehensive study of the phase transition process by using first-principles energetic and phonon calculations within the quasi-harmonic approximation framework. We predicted that the phase transition from h-GaTe to m-GaTe occurs at the temperature decreasing to 261 K. This is in qualitative agreement with the experimental observations. It is a two-step transition process with energy barriers 199 meV and 288 meV, respectively. The relatively high energy barriers demonstrate the irreversible nature of the phase transition. The electronic and phonon properties of the two phases were further investigated by comparison with available experimental and theoretical results. Our results provide insightful understanding on the process of temperature-induced phase transition of GaTe.

Temperature-induced Lifshitz transitions have been identified in several materials. Their chemical potential shows a substantial shift with changing temperature. The common feature of these materials is the coexistence of electron and hole pockets in the vicinity of the chemical potential. Here, we report the observation of temperature-induced chemical potential shift and Lifshitz transition in a layered type-II Weyl semimetal, TaIrTe4. The reversal of the polarity of the Hall resistivity and thermoelectric power (TEP) as the temperature increases clearly signal an appreciable shift of the chemical potential and change of the Fermi surface. It is corroborated by the improving agreement between the experimental TEP and the one calculated with temperature-dependent chemical potential. The complete disappearance of an electron pocket, consistent with the change of the Fermi surface when the chemical potential moves downwards, provides an evident signature of a temperature-induced Lifshitz transition in TaIrTe4.

The friction and wear behavior of an Mg-10Gd-1.4Y-0.4Zr alloy were investigated in detail within a temperature range of 20 °C–200 °C in order to clarify temperature-induced mild-severe (M-S) wear transition mechanism and verify if contact surface dynamic recrystallization (DRX) temperature criterion can be applicable to elevated temperature M-S wear transition. Coefficient of friction (COF) and wear rate (WR) were plotted against applied load at each test temperature, from which M-S wear transition loads were identified. A wear mechanism transition map was created on test temperature-applied load coordinate system, in which the mild wear region i.e. a safe working region in engineering application was indicated. The M-S wear transition mechanism was proved to be DRX softening by microstructural examination and hardness measurement in subsurfaces. The effects of precipitation and static recrystallization (SRX) occurred at temperatures of 150 °C–200 °C on M-S wear transition were also assessed. According to surface DRX temperature criterion, the transition loads were calculated at temperatures of 20 °C–200 °C, and the results identified applicability of the criterion to wear tests at elevated temperatures.

The pyroelectric response of materials is a promising phenomenon that is used in many applications, but two-dimensional (2D) pyroelectricity has not received due attention. Here we report ab initio molecular dynamics simulations to investigate the pyroelectric effect in α-III2VI3 (III = Al, Ga, In; VI = S, Se) monolayers, an emerging class of 2D pyroelectric materials. The in-plane and out-of-plane spontaneous polarizations are found to be robust at room temperature. We demonstrate large pyroelectric response in these materials that is associated with temperature-induced ferroelectric-to-paraelectric phase transitions. Identifying the high-temperature nonpolar phase as the β-phase, we demonstrate strong displacive character in the α-β phase transition, which is achieved through relative displacements of the top three and bottom two atomic sublayers in opposite directions. The present work unravels and highlights the primary pyroelectric effect and the α-β phase transitions that are responsible for the promising pyroelectricity in α-III2VI3 monolayers.

Detailed magnetic studies of polycrystalline GdCrO3 show a spectrum of interesting features, such as temperature induced magnetization reversal, spin flipping and spin reorientation, etc, which arise due to the competing magnetic interactions within and between Cr and Gd-sublattices. It also exhibits a giant magnetocaloric effect (MCE) with a maximum entropy change of 36.97 J kg−1 K−1, an adiabatic temperature change of 19.12 K and a refrigeration capacity of 542 J kg−1 for a field change of 7 T at low temperatures. Such an exceptionally large MCE arises from the suppression of the spin entropy associated with the suppression of spin reorientation transition, in addition to the Gd-ordering, which makes it one of the best candidates for magnetic refrigeration among all known potential low temperature magnetic refrigerants.

The author estimates stress state in steel-and-concrete power conduit arranged at the concrete downstream face with regard to temperature and combination of loads. It is shown that the maximal tensile stresses are formed under minimum temperature in winter at the conduit points remote from the downstream face.

Exploring nature of liquid structures and properties is becoming more interesting in various fundamental and applied fields. With different resorts including the resistivity method, temperature-induced liquid-liquid structure transitions (TI-LLST) have been suggested and verified to occur in some liquid alloys, while the reversibility of TI-LLST has rarely been examined as yet. Unlike some other investigated liquid alloys, here we show that electrical resistivity of Pb26Sn42Bi32 melt exhibit an anomalous change in the first heating run and a reversible change in the following cooling and heating cycles. Taking account of the structural sensitivity of electrical resistivity, the abnormal patterns suggest two sorts of TI-LLST that are irreversible and reversible in the liquid ternary alloy, respectively. This interesting phenomenon together with other growing evidence imply that liquid structures and their change characteristics are multiform and complex.

Polarized Raman spectra of ferroelectric relaxor 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (0.67PMN-0.33PT) single crystal are systematically investigated in a wide temperature range from -196 to 600°C by micro-Raman scattering technique. The results clearly reveal that there are two structural phase transitions in such composite ferroelectric relaxor: the rhombohedral-tetragonal (R - T) phase transition and the tetragonal-cubic (T - C) phase transition. The former occurs at about TR-T = 34°C, corresponding to the vanishing of the soft A1 mode at 106 cm−1 recorded in the parallel polarization. The latter appears at about TT-C = 144°C, which can be verified with the vanishing of mode at 780 cm−1 measured in the crossed polarization.

Element-specific magnetic properties of ultrathin epitaxial Co2FeSi(110) films were measured using x-ray magnetic circular dichroism (XMCD). The epitaxial Heusler films were grown by RF magnetron sputtering on substrates. The magnetization of thicker films as determined by XMCD is smaller than expected for a half-metallic material. In addition, the magnetization decreases considerably for films thinner than 10 nm. The thickness dependence of the magnetic moment can be described by introducing a certain number of dead layers representing a deficiency of magnetization at the interfaces. Quantitative evaluation results in a dead layer thickness of 0.8 nm at room temperature, consisting of a temperature induced size effect of 0.1 nm and a surface effect of 0.15 nm at the top and 0.55 nm at the bottom interface.

The structure and magnetocaloric effect (MCE) of rapidly quenched LaFe11.4Si1.6 compound were investigated by means of x-ray diffraction analyses and magnetic measurements. The rapid quenching greatly facilitates the formation of the cubic La(Fe,Si)13 (1:13 structure) in LaFe11.4Si1.6 alloy. Rietveld analyses indicate that about 22 wt% of the 1:13 phase is formed in rapidly quenched LaFe11.4Si1.6 alloy. A subsequent very brief annealing (1273 K/20 min) of the as-quenched alloy is sufficient for the formation of a single-phase 1:13 structure. Magnetic behaviour near TC indicates the occurrence of a field induced magnetic transition above TC, which is responsible for the large magnetic entropy change ΔS in annealed rapidly quenched LaFe11.4Si1.6 alloy. Comparing with annealed arc melted alloy, the annealed rapidly quenched alloy shows a smaller ΔS at or slightly below TC, where the magnetocaloric effect mainly originates from the temperature induced magnetic transition. On the other hand, the peaks of ΔS above TC for the two alloys are almost identical, which is mainly due to the field induced magnetic transition. The results indicate that ΔS due to a temperature induced magnetic transition is sensitive to the microstructure while the MCE related to a field induced magnetic transition is not.

We report an optical spectroscopy study on LaSb, a compound recently identified to exhibit extremely large magnetoresistance. Our optical measurement indicates that the material has a low carrier density. More interestingly, the study reveals that the plasma frequency increases with decreasing temperature. This phenomenon suggests either an increase of the conducting carrier density or/and a decrease of the effective mass of carriers with decreasing temperature. We attribute it primarily to the latter effect. Two possible scenarios on its physical origin are examined and discussed. The study offers new insight into the electronic structure of this compound.

We observed the decrease of the hysteresis effect and the transition from the stable to the dynamic domain regime in doped superlattices with increasing temperature. The current–voltage characteristics and the behaviours of the domain boundary are dominated by the temperature-dependent lineshape of the electric field dependence of the drift velocity (V (F )). As the peak–valley ratio in the V( F )curve decreases with increasing temperature, the hysteresis will diminish and temporal current self-oscillations will occur. The simulated calculation, which takes the difference in V( F )curves into consideration, gives a good agreement with the experimental results.

In this paper we have considered the effect of temperature on the thermoelectric current in a one-dimensional ballistic ring coupled to two electron reservoirs. It is also shown that under some conditions a circulating thermoelectric current highly exceeds the transport current.

Cobalt- and nickel-rich nanoparticles were produced by direct segregation from a single crystal rutile TiO2 in ultra-high vacuum conditions. It was shown that, similarly to the previous findings for Fe, also in the case of Co and Ni, the segregation of a noticeable amount of material is possible on the (001) surface. Segregation of these metals results in formation of nanoparticles and their distribution on the surface partially reflects the substrate symmetry in the case of Co and reveals some signs of self-organization for Ni. Cyclic appearance and disappearance of Co- and Ni-rich nanoparticles can be fully controlled by the temperature of annealing. The explanation of the mechanism of repeatable segregation is proposed basing on interaction of Co and Ni cations with Ti interstitials. These new findings can be especially important for catalysis and spintronic applications where the controlled nanoparticles size and concentration are crucial.

Ultrasonic P wave velocity (VP) and quality factor (QP value, on behalf of attenuation) in pyroxenite were presented as functions of pressures (0.3-3.0 GPa) and temperatures (20-1170°C). The experimental results show that VP and QP depend upon pressure and temperature. VP and QP in pyroxenite increase more rapidly at the pressure 0.3-1.4 GPa than those at 1.4-3.0 GPa. As the temperature rising from 20°C to about 1170°C at the pressure 3.0 GPa, an almost linear decrease up to 11% in VP was observed, and QP drops from 243 at room temperature to 68 at 1170°C with decreasing 72%. The experimental data indicate that the pressure and temperature induced fabric changes and frictional sliding and dislocation in pyroxenite play a key role in wave propagation in rocks.

This paper reports the 450 nm up-conversion fluorescence of the crystalline TmP5O14 at room temperature induced by pulsed DCM dye laser. It is found that the up-conversion mechanism is the excited state absorption.

Based on the arrangement of two-dimensional 'melon', we construct a unit cell for polymeric carbon nitride (PCN) synthesized via thermal polycondensation, whose theoretical diffraction powder pattern includes all major features measured in x-ray diffraction. With the help of this unit cell, we describe the process-temperature-induced crystallographic changes in PCN that occur within a temperature interval between 510 and 610 °C. We also discuss further potential modifications of the unit cell for PCN. It is found that both triazine- and heptazine-based g-C3N4 can only account for minor phases within the investigated synthesis products.

Both increased temperature and moderate concentrations of fluorinated alcohols enhance aggregation of the Parkinson's disease-associated protein α-synuclein (αS). Here, we investigate the secondary structural rearrangements induced by heating and trifluoroethanol [TFE]. At low TFE concentrations, CD spectra feature a negative peak characteristic of disordered polypeptides near 200 nm and a slight shoulder around 220 nm suggesting some polyproline-II content. Upon heating, these peaks weaken, while a weak negative signal develops at 222 nm. At high TFE concentrations, the spectra show distinct minima at 208 and 222 nm, indicative of considerable α-helical structure, which diminish upon heating. We observe a crossover between the low-TFE and high-TFE behavior near 15% TFE, where we previously showed that a partially helical intermediate is populated. We postulate that the protein is well solvated by water at low TFE concentrations and by TFE at high TFE concentrations, but may become desolvated at the crossover point. We discuss the potential roles and interplay of desolvation and helical secondary structure in driving αS aggregation.

The influence of the annealing atmosphere on the temperature induced phase separation of Ge oxide in GeO(x)/SiO(2) multilayers (x≈1), leading to size controlled growth of Ge nanocrystals, is explored by means of x-ray absorption spectroscopy at the Ge K-edge. Ge sub-oxides contained in the as-deposited multilayers diminish with increasing annealing temperature, showing complete phase separation at approximately 450 °C using inert N(2) ambient. The use of reducing H(2) in the annealing atmosphere influences the phase separation even at an early stage of the disproportionation. In particular, the temperature regime where the phase separation occurs is lowered by at least 50 °C. At temperatures above 400 °C the sublayer composition, and thus the density of the Ge nanocrystals, can be altered by making use of the reduction of GeO(2) by H(2).

Photoluminescence (PL) measurements were employed to investigate the emission properties of uncapped InN nanodot samples grown at temperature from 550 to 725 °C. Our results indicate that once the In droplets are formed, the optical properties of InN dots deteriorate markedly. As for those droplet-free samples grown at temperatures ≥600 °C, good luminescence properties are obtained. The corresponding 20 K PL peak energy is found to be almost constant at approximately 0.77 eV with a slow increase in its linewidth from 71 to 74 meV. A strong temperature-induced energy blue shift at approximately 20 to 280 K is considered to be partially connected to the band-filling effects of thermally stimulated surface electrons.

The excitonic fine structure of silicon nanoparticles is investigated by time-resolved and magnetic-field–dependent photoluminescence. The results are analyzed using the common model of an excitonic fine structure consisting of a bright and a dark exciton. We find that the radiative recombination rates of both excitons differ only by a factor of eight. Therefore, we observe a thermal crossover in the character of the emission from bright-exciton-like to dark-exciton-like. The validity of our model is further supported by magnetic-field–dependent measurements, in which effects of state mixing are observed.

Using a simple ionic model and thermodynamic arguments, the thermal expansion of SmS at high pressures is analysed. In this manner it is shown that the experimentally observed temperature-induced phase transition, from a metallic state with intermediate valence, to a semiconducting state, both on heating and cooling, can be accounted for. A formula is derived which enables the intermediate valence of the Sm ions, corresponding to extrema on the thermal expansion curves, to be deduced. The nature of the transitions and the critical temperature are also discussed.

The deformable shell model has been used for the calculation of phonon dispersion in CsCl with both ions polarisable. The temperature-induced phase transition and equation of state of CsCl have also been studied. Inclusion of polarisability of the positive ion in calculating phonon dispersion removes almost completely the discrepancies reported earlier by Ghosh and Basu (1976). The results for phase transition temperature and equation of state calculation agree fairly well with experiment.

Random walks on tree structures are as useful tools in physics as they are interesting themselves. Here we show that for a certain class of models they can undergo a transition from being recurrent to being transient depending on the temperature. At the transition the relaxation is logarithmic. The significance of the pole in the relaxation exponent is also discussed.

The structure and growth conditions of aging-induced precipitations in polycrystalline near equiatomic NiTi are examined by neutron powder diffraction. The molar amount of the precipitates after different heat treatments is determined. The influence of stoichiometry on crystallisation and other physical properties are discussed.

The magnetizations of a mixed Ising ferrimagnetic system consisting of spin-½ and spin-1 with different transverse fields are investigated. We find that a compensation point induced by the different transverse fields is obtained as well as the typical temperature dependences of magnetization usually found in crystalline ferrimagnetic alloys, although the system never exhibits any compensation point for the zero transverse fields.

Y2Ni7, which is pararragnetic at T=0, becomes ferromagnetic when the temperature is raised to ∼7K; then at ∼60K the system again makes a phase transition to paramagnetic state. We show how it is possible to understand such a behavior of an itinerant electron system if we take into account the effect of the electron-phonon interaction.

Irradiation with 1.5 MeV electrons slightly below room temperature induced the transformation of about half (≃1.7×1014 cm-3) of quenched-in shallow acceptors (SA2) at E v+13 meV into more shallow acceptors at E v+9 meV. These new acceptors returned to the SA2 acceptors after annealing around 300°C. The irradiation also caused a decrease (≃4×1014 cm-3) in substitutional-copper density. Part of the annihilated copper atoms reappeared after annealing around 300°C, suggesting that various defect complexes involving copper were formed by the irradiation.