Room Temperature Annealing Research Articles

Compressed H3S: inter-sublattice Coulomb coupling in a high-TC superconductor

Upon thermal annealing at or above room temperature (RT) and at high hydrostatic pressure P ~ 155 GPa, sulfur trihydride H3S exhibits a measured maximum superconducting transition temperature TC ~ 200 K. Various theoretical frameworks incorporating strong electron–phonon coupling and Coulomb repulsion have reproduced this record-level TC. Of particular relevance is that experimentally observed H–D isotopic correlations among TC, P, and annealed order indicate an H–D isotope effect exponent α limited to values ⩽ 0.183, leaving open for consideration unconventional high-TC superconductivity with electronic-based enhancements. The work presented herein examines Coulombic pairing arising from interactions between neighboring S and H species on separate interlaced sublattices constituting H3S in the Imm structure. The optimal value of the transition temperature is calculated from TC0 = Λe2/ζ, with Λ = 0.007465 Å, inter-sublattice S–H separation spacing ζ = a0/, interaction charge linear spacing = a0 (3/σ)1/2, average participating charge fraction σ = 3.43 ± 0.10 estimated from calculated H-projected electron states, and lattice parameter a0 = 3.0823 Å at P = 155 GPa. The resulting value of TC0 = 198.5 ± 3.0 K is in excellent agreement with transition temperatures determined from resistivity (196–200 K onsets, 190–197 K midpoints), susceptibility (200 K onset), and critical magnetic fields (203.5 K by extrapolation). Analysis of mid-infrared reflectivity data confirms the expected correlation between boson energy and ζ−1. Suppression of TC below TC0, correlating with increasing residual resistance for < RT annealing, is treated in terms of scattering-induced pair breaking. Correspondences between H3S and layered high-TC superconductor structures are also discussed, and a model considering Compton scattering of virtual photons of energies ⩽ e2/ζ by inter-sublattice electrons is introduced, illustrating that Λ ∝ ƛC, where ƛC is the reduced electron Compton wavelength.

Effect of corona discharge on cadmium sulphide and lead sulphide films

ABSTRACTThis paper describes the effect of corona discharge on cadmium sulphide (CdS) and lead sulphide (PbS) films prepared using the chemical route. The property of films before and after exposure to corona has been described in detail. The electronic properties of the CdS and PbS films have been studied by current-voltage (I-V), capacitance-voltage (C-V) measurements. The structural properties and surface morphology were studied by using X-ray diffraction and scanning electron microscopy before and after exposing to Corona discharge. The films displayed the change in surface morphology after exposure to the corona discharge. It has been found that the films showed an increase in resistivity after exposure. This change in property has been attributed to modification in surface states. Time-dependent recovery indicated that room temperature annealing is sufficient to regain the normal resistivity of the films. The experiment was carried with the aim of studying the effect of the interaction of corona discharge on the semiconductor films and its subsequent effects.

Measurements of the reverse current of highly irradiated silicon sensors to determine the effective energy and current related damage rate

The reverse current of irradiated silicon sensors leads to self heating of the sensor and degrades the signal to noise ratio of a detector. Precise knowledge of the expected reverse current during detector operation is crucial for planning and running experiments in High Energy Physics. The dependence of the reverse current on sensor temperature and irradiation fluence is parametrized by the effective energy and the current related damage rate, respectively. In this study 18 n-in-p mini silicon strip sensors from companies Hamamatsu Photonics and Micron Semiconductor Ltd. were deployed. Measurements of the reverse current for different bias voltages were performed at temperatures of −32°C, −27°C and −23°C. The sensors were irradiated with reactor neutrons in Ljubljana to fluences ranging from 2×1014neq∕cm2 to 2×1016neq∕cm2. The measurements were performed directly after irradiation and after 10 and 30 days of room temperature annealing. The aim of the study presented in this paper is to investigate the reverse current of silicon sensors for high fluences of up to 2×1016neq∕cm2 and compare the measurements to the parametrization models.

Precipitation of secondary phase in Mg-Zn-Gd alloy after room-temperature deformation and annealing

Mg-Zn-RE alloys reinforced with quasicrystals have been investigated extensively because they show excellent balance in mechanical properties. Here, we perform deformation and annealing for Mg-1.50Zn-0.25Gd (at.%) alloy at various temperatures, aimed to gain nanoscale precipitates. We find that after the room-temperature compression, the non-basal dislocation, stacking fault and twining are identified in the as-deformed samples, offering clear evidence that these deformation mechanisms can accommodate room-temperature deformation. We also perform systematic transmission electron microscopy observations of the precipitates in both the as-deformed and as-annealed samples. The results identify the formation of a large amount of secondary-phase precipitates, I-phase and MgZn2, when annealed at 200°C, and precipitation of a small amount of W-phase when annealed at 400°C.

Quantification of germanium-induced suppression of interstitial injection during oxidation of silicon

The oxidation of silicon is known to inject interstitials, and the presence of silicon–germanium (SiGe) alloys at the Si/SiO2 interface during oxidation is known to suppress the injection of silicon self-interstitials. This study uses a layer of implantation-induced dislocation loops to measure interstitial injection as a function of SiGe layer thickness. The loops were introduced by a 50 keV 2 × 1014 cm−2 P+ room-temperature implantation and thermal annealing. Germanium was subsequently introduced via a second implant at 3 keV Ge+ over a range of doses between 1.7 × 1014 cm−2 and 1.4 × 1015 cm−2. Results show that upon oxidizing at 850 °C for 3 h or 900 °C for 70 min to condense the germanium at the Si/SiO2 interface, where if forms a Si0.5Ge0.5 alloy. Upon subsequent oxidations of 850 °C for 6 h or 900 °C for 2 h, partial suppression of interstitial injection can be observed for sub-monolayer doses of germanium, and more than three monolayers of Si0.5Ge0.5 (1.4 × 1015 cm−2) are necessary to suppress interstitial injection below the detection limit during oxidation. These results show that low-energy implantation of germanium can be used to eliminate or modulate injection of oxidation-induced interstitials.

Conductivity relaxation in strongly underdoped [formula omitted] single crystals

Temperature dependences of the basal-plane electrical resistance of underdoped YBa2Cu3Ot−δ single crystals are investigated in a broad temperature range down to the superconducting transition, after a fast cooldown from 650° C as well as after a room-temperature annealing. A stepped behavior of the superconducting transition has been observed, pointing to an inhomogeneity of the samples. Annealing has been revealed to lead to a narrowing of the superconducting transition and a reduction of both, the residual resistivity and the phonon scattering coefficient. This is accompanied by a slight increase of the Debye temperature attributed to a decrease of the lattice parameter caused, in turn, by a redistribution of the labile oxygen. The revealed changes of the parameters of the temperature dependence of the electrical resistance point to an equalization of the concentration of the labile oxygen in the layers and its ordering.

On the isotope effect in compressed superconducting H3S and D3S

A maximum superconductive transition temperature TC = 203.5 K has recently been reported for a sample of the binary compound tri-hydrogen sulfide (H3S) prepared at high pressure and with room temperature annealing. Measurements of TC for H3S and its deuterium counterpart D3S have suggested a mass isotope effect exponent α with anomalous enhancements for reduced applied pressures. While widely cited for evidence of phonon-based superconductivity, the measured TC is shown to exhibit important dependences on the quality and character of the H3S and D3S materials under study; examination of resistance versus temperature data shows that variations in TC and apparent α are strongly correlated with residual resistance ratio, indicative of sensitivity to metallic order. Correlations also extend to the fractional widths of the superconducting transitions. Using resistance data to quantify and compensate for the evident materials differences between H3S and D3S samples, a value of α = 0.043 ± 0.140 is obtained. Thus, when corrected for the varying levels of disorder, the experimental upper limit (≤0.183) lies well below α derived in phonon-based theories.

Rapid and long-term gamma-radiation annealing in low-dropout voltage regulators

Samples of four types of low-dropout voltage regulators, with both serial pnp and npn transistors, were examined in room-temperature isothermal gamma radiation annealing. After uninterrupted exposure to a total ionising dose of 500 Gy, biased and loaded voltage regulators were examined in room-temperature annealing within the first 30 minutes after the exposure. Beside the on-line measurement of output voltage and quiescent current during the thirty-minute period immediately after irradiation, also results were procured after 10-year room-temperature spontaneous recovery. Data obtained during the irradiation and rapid annealing were fitted with linear, exponential, and power-law regression functions. A simple procedure was proposed, based on the quiescent current annealing factor, for the quick estimation of the integrated voltage regulator's radiation sensitivity during the post-irradiation isothermal annealing. In order to estimate the circuit's radiation sensitivity, immediately after irradiation, tested devices have to be left in the same operating conditions as during the exposure. If a clear trend of the quiescent current recovery can be observed, further examinations have to be implemented to estimate if a circuit is acceptably radiation-tolerant. If no recovery trend can be observed within the first hour after irradiation, or even further degradation is noticed, then the examined voltage regulator is a radiation-sensitive device and cannot be used in radiation environments. The described procedure is based on the macroscopic effects of the radiation-induced charge-trapping in field oxides and interfaces. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 171007: Physical and functional effects of the interaction of radiation with electrical and biological systems] &lt;br&gt;&lt;br&gt;&lt;font color="red"&gt;&lt;b&gt; This article has been corrected. Link to the correction &lt;u&gt;&lt;a href="http://dx.doi.org/10.2298/NTRP1703305E"&gt;10.2298/NTRP1703305E&lt;/a&gt;&lt;u&gt;&lt;/b&gt;&lt;/font&gt;

Deuterium retention in tungsten simultaneously damaged by high energy W ions and loaded by D atoms

Deuterium retention was for the first time measured in tungsten samples simultaneously irradiated by W ions and exposed to D atoms at five different temperatures from 450K to 1000K. In order to obtain information on the defect concentration, samples were afterwards exposed to D atoms at 600K to populate the created defects. The results were compared to different sequential damaging/exposure experiments. Synergistic effects were observed, namely, higher D concentrations were found in the case of simultaneous damaging and D-atom loading as compared to sequential damaging at elevated temperatures and populating the defects afterwards. However, the deuterium retention is still lower as compared to sequential damaging at room temperature and post-damaging annealing. The observations are explained by stabilization of defects by the presence of solute hydrogen in the bulk that would annihilate at high temperatures without the presence of hydrogen. Results of simultaneous W-ion damaging and D exposure at elevated temperatures were also compared to a sequential experiment of W-ion damaging at room temperature and then D-atom loading at high temperatures showing that thermal D de-trapping dominates deuterium retention at high temperatures.

Tuning the microstructure and magnetic properties of bulk nanocomposite magnets with large strain deformation

In this study, we investigated the effect of strain on the microstructure and magnetic properties of bulk α-Fe/Nd2Fe14B nanocomposite magnets produced by a combination of severe plastic deformation at room temperature and subsequent thermal annealing. Experiment results indicate that severe plastic deformation can induce the formation of α-Fe and Nd2Fe14B nanocrystals in the amorphous matrix and then suppress the formation of metastable intermediate phases during thermal annealing. The volume fraction of α-Fe phase in the magnets increases as the strain increases，and the grain size of α-Fe and Nd2Fe14B phases significantly decreases. As a result, the bulk magnets made at ε=6.2 show enhanced magnetic properties, (BH)max=17.8 MGOe and Hc=7.2kOe, compared with that of directly annealed partially amorphous (Nd-Pr)-Fe-Co-Nb-B, (BH)max=12.2 MGOe and Hc=6.2kOe.

Controlled thermodynamics for tunable electron doping of graphene on Ir(111)

The electronic properties and surface structures of K-doped graphene supported on Ir(111) are characterized as a function of temperature and coverage by combining low-energy electron diffraction, angle-resolved photoemission spectroscopy, and density functional theory (DFT) calculations. Deposition of K on graphene at room temperature (RT) yields a stable $(\ensuremath{\surd}3\ifmmode\times\else\texttimes\fi{}\ensuremath{\surd}3)$ R30\ifmmode^\circ\else\textdegree\fi{} surface structure having an intrinsic electron doping that shifts the graphene Dirac point by ${E}_{D}=1.30\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ below the Fermi level. Keeping the graphene substrate at 80 K during deposition generates instead a $(2\ifmmode\times\else\texttimes\fi{}2)$ phase, which is stable until full monolayer coverage. Further deposition of K followed by RT annealing develops a double-layer K-doped graphene that effectively doubles the K coverage and the related charge transfer, as well as maximizing the doping level $({E}_{D}=1.61\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$. The measured electron doping and the surface reconstructions are rationalized by DFT calculations. These indicate a large thermodynamic driving force for K intercalation below the graphene layer. The electron doping and Dirac point shifts calculated for the different structures are in agreement with the experimental measurements. In particular, the ${\mathrm{K}}_{4s}$ bands are shown to be sensitive to both the K intercalation and periodicity and are therefore suggested as a fingerprint for the location and ordering of the K dopants.

Тhe transformation of the oxide coatings of aluminum by imitation factors of nuclear power plants

The authors present the results of a study on kinetics of hydrogen generation by heterogeneous compositions with aluminum exposed to γ-irradiation in air, in different aqueous solutions at room temperature and high temperature annealing. It has been found that hydrogen generation kinetics depends on the γ-irradiation dose, temperature and aqueous medium chemistry. Changes in hydrogen generation kinetics are due to transformations of aluminum oxide coatings influenced by factors simulating the NPP conditions. The effect of metal oxide coating transformations should be considered in predicting the corrosion resistance of NPP structural materials.

In situ GISAXS study of a Si-containing block copolymer under solvent vapor annealing: Effects of molecular weight and solvent vapor composition

The room-temperature solvent vapor annealing of polystyrene-b-polydimethylsiloxane (PS-b-PDMS) block copolymer films was studied in situ by grazing incidence small-angle X-ray scattering. Films of cylinder-forming PS-b-PDMS with molecular weight 16 kg/mol and 12.2 kg/mol, annealed under vapors of toluene:heptane with varying composition, exhibited swelling-ratio-dependent evolution of microdomain spacing and orientation. In a vapor made from a toluene:heptane 5:1 volumetric ratio liquid mixture, or from pure toluene, cylindrical microdomains reoriented from majority out-of-plane to in-plane during annealing, while drying led to shrinkage along the film normal and a large distortion of the hexagonal lattice of in-plane cylinders. Annealing under vapor from a toluene:heptane 1:5 volumetric ratio liquid produced a non-bulk lamellar structure in the 16 kg/mol PS-b-PDMS.

The Mechanical Properties of the Mo-0.5Ti and Mo-0.1Zr Alloys at Room Temperature and High Temperature Annealing

Abstract Mo-0.5Ti and Mo-0.1Zr alloys were prepared by powder metallurgy. In Mo-0.5Ti and Mo-0.1Zr alloys, there appears the second-phase particles of Ti2O3 and ZrO2 respectively, each of which can effectively prevent the dislocation activity in the process of plastic deformation. The addition of Zr can increase the strength of molybdenum alloys. Meanwhile, the ZrO2 formed from the alloy element Zr can refine the grains of molybdenum alloys to improve the recrystallization plasticity. After annealing, the tensile strength decreases while the plasticity greatly increases compared to the annealed Mo-0.5Ti and Mo-0.1Zr alloys. With the increase of annealing temperature, both the tensile strength and plasticity of Mo-0.5Ti and Mo-0.1Zr alloys decrease. Compared with pure Mo, after annealing the properties of the Mo-0.5Ti alloy and the plasticity of the Mo-0.1Zr alloy significantly increases.

Effect of substrate temperature and post-deposition annealing on intrinsic a-SiOx:H film for n-Cz-Si wafer passivation

In order to make sure the co-operation of substrate temperatures and post-deposition annealing on the structure and performance of the a-SiOx:H for n-Cz-Si wafer passivation, three series a-SiOx:H films bifacial-deposited on n-Cz-Si wafers were made. In which, the first series was deposited at room temperature and post-deposition annealing with different temperature; the second series was deposited with different substrate temperature and without post-annealing; and the third series was deposited with different substrate temperature and post-annealed at the optimized 275 °C. Effective lifetime of the samples was tested by QSSPC method, and the imaginary part of dielectric constant (e 2) and film properties of the films were analyzed by Spectroscopic Ellipsometry and Fourier Transform Infrared Spectroscopy. It is concluded that (1) the structure and passivation effect of a-SiOx:H films on n-Cz-Si wafer are sensitive to the substrate temperature and post-deposition annealing, and the optimum scheme is depositing the film at 100 °C and post-annealing the wafer at 275 °C; (2) the microstructure parameter R * of the a-SiOx:H is ~0.67 for the samples with the optimum passivation effect.

SnS thin films prepared by H2S-free process and its p-type thin film transistor

Polycrystalline SnS thin films were fabricated by a H2S-free process combing pulsed laser deposition at room temperature and post-deposition thermal annealing in Ar. Thermal annealing improved the crystalline quality of the SnS films and the best films were obtained by 400 °C annealing. The obtained SnS films exhibited p-type conduction with the highest Hall mobility of 28 cm2/(V ⋅ s) and the carrier densities of 1.5 × 1015 – 1.8 × 1016 cm−3. The SnS TFT exhibited p-type operation with a field effect mobility and an on-off drain current ratio of 0.4 cm2/(V ⋅ s) and 20, respectively.

In Situ Characterization of the Self-Assembly of a Polystyrene–Polydimethylsiloxane Block Copolymer during Solvent Vapor Annealing

Grazing incidence X-ray scattering was used to follow the microphase separation during room-temperature solvent annealing of films of high interaction parameter cylinder-forming 16 kg/mol polystyrene-b-polydimethylsiloxane block copolymer in a toluene–heptane mixed solvent vapor. Microphase separation was observed for swelling ratios above 1.2, but swelling ratios above 1.9 caused the films to disorder. The films exhibited a thickness-dependent microdomain reorientation during annealing, with the initial out-of-plane cylinder orientation converting to an in-plane orientation as a result of preferential surface interactions. Drying led to a reduction in the out-of-plane cylinder spacing, with slower drying leading to greater deswelling and larger distortion of the hexagonal lattice.

Detection of dead layers and defects in polycrystalline Cu2O thin-film transistors by x-ray reflectivity and photoresponse spectroscopy analyses

Polycrystalline Cu2O films were fabricated on amorphous SiO2 glass by pulsed laser deposition at room temperature and postdeposition thermal annealing in N2 + O2 mixing gases. The authors made a phase map in annealing temperature (Tann) vs RO2 = [O2]/([O2] + [N2]) ratio and found that highly pure Cu2O films were obtained at RO2 ∼ 0.002%. The increase in Tann improved the crystal quality of the Cu2O films, and the maximum Hall mobility of ∼26 cm2/(V s) was obtained at 700 °C. Bottom-gate Cu2O thin-film transistors (TFTs) using the optimum Cu2O channels exhibited clear p-type operation; however, the largest field effect mobility is as small as the order of 10−2 cm2/(V s), indicating the existence of high-density hole trap states. Several subgap states were observed by optical absorption spectra of films and photoresponse spectroscopy of the TFTs. X-ray reflectivity analysis detected a low-density dead layer at the Cu2O–SiO2 glass substrate interface, which would be attributed to Cu diffusion into the glass substrate.

Recovery of the Electrical Characteristics of SiC MOSFETs Irradiated with Gamma-Rays by Thermal Treatments

Effects of gamma-ray irradiation and subsequent thermal annealing on the characteristics of vertical structure power Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) fabricated on 4H-SiC were studied. After irradiation at 1.2 MGy, the drain current – gate voltage curves of the MOSFETs shifted to the negative voltage side and the leakage drain current at inverse voltage increased. No significant change in the degraded electrical characteristics of SiC MOSFETs was observed by room temperature annealing. The degraded characteristics of SiC MOSFETs began to recover by annealing above 120 °C, and their characteristics reached almost the initial ones by annealing at 360 °C.

Dose response, radiation sensitivity and signal fading of p-channel MOSFETs (RADFETs) irradiated up to 50 Gy with 60Co

This paper reports response of p-channel MOSFETs (RADFETs) to 60Co gamma radiation in the 10–50Gy dose range and signal fading (room temperature annealing) for 100 days after irradiation. RADFETs with three different thicknesses of the gate oxide layer were used. Irradiations were performed at gate biases ranging from 0 to 5V. Threshold voltage shift was monitored during the irradiations and the subsequent fading. The dependence of the threshold voltage shift on the radiation dose is linear for the RADFETs with 100nm- and 400nm-thick gate oxide layers irradiated under the gate biases ranging from 1.25 to 5V. Also, an exponential dependence of the radiation sensitivity on the gate bias during irradiation was found. The signal fades at room temperature without a gate bias. The results demonstrate that these RADFETs are suitable as sensors of gamma radiation. The threshold voltage shift of the RADFETs with 400nm- and 1μm-thick gate oxide layers decreases significantly during the first day after irradiation, which, unfortunately, makes these devices incapable of holding dosimetric information for long periods of time.