Annealing Of Radiation-induced Defects Research Articles

The influence of 2 at. % Si addition on the annealing of radiation-induced defects in the Fe-13Cr alloy

The paper presents data on electrical resistivity recovery in the Fe-13.4Cr and Fe13.6Cr-1.9Si alloys during isochronal annealing after 5 MeV electron irradiation below 77 K. Long-range migration of radiation-induced defects starts slightly above 200 K in Fe-13.4Cr. The silicon addition in Fe13.6Cr-1.9Si leads to immobilization of Frenkel pair defects thus making the peaks of the stages of the onset of long-range migration shift towards high temperatures up to 370 K and 420 K for self-interstitial atoms and vacancies, respectively. This finding confirms the data obtained earlier for Fe16Cr-Si alloys by means of positron annihilation technique (JNM 508(2018) 100–106) on trapping of radiation-induced defects on Si agglomerates (clusters consisting of several silicon atoms) formed during defect migration.

Structure, Composition, and Properties of Zn- and O-Ion Implanted Silicon at Elevated Temperatures

Czochralski-grown Si substrates (n-type, orientation (100)) are subjected to double implantation, notably, initially by 64Zn+ ions with a dose of 5 × 1016 cm–2 and an energy of 50 keV and then with 16O+ ions with a dose of 2 × 1017 cm–2 and an energy of 20 keV. The substrates during implantation are held at ~350°C. The implanted Si substrates contain radiation-induced defects and their clusters such as twins, dislocations, and nanoclusters, notably, Zn-containing nanoclusters with an average radius of 10–50 nm predominantly consisting of the metallic Zn phase and partially from the ZnO phase formed on the surface and in the substrate near-surface layer. Photonic annealing to an effective temperature of 700°C optimal for the formation of the ZnO phase leads to the annealing of radiation-induced defects, and Zn-containing nanoclusters presumably consisting of the ZnO phase and partially of the Zn2SiO4 phase with an average diameter of 50–100 nm are recorded on the sample surface.

Simulation of Self-sustained Relaxation of a Two-dimensional Metastable Medium by Means of a Traveling Wave

The traveling wave mode of self-sustained relaxation of a metastable medium, such as combustion and annealing of radiation-induced defects in solids, is studied. The mechanism of self-sustained relaxation and propagation of the traveling wave is a positive thermal-concentration feedback and heat transfer. The thermal-concentration feedback develops because the relaxation rate depends strongly on temperature, and the energy of the metastable state transforms into thermal energy in the process of relaxation. Hence, the relaxation leads to an increase in the medium temperature and, consequently, to further support of the relaxation. In this work, traveling waves are considered, and their features are investigated by computer simulation. The shape and speed of the traveling wave are investigated as a function of the medium properties, and the way of its initiation. We examined the shapes of wavefronts as they propagate on a plane, and observed two different regimes of traveling wave propagation. Sometimes the front of the traveling wave spreads as a whole and velocity of propagation is perpendicular to the wavefront. Sometimes small perturbations arise on the wavefront, and then grow by virtue of relaxation along the front, thus, the new area of the relaxed medium has the form of a narrow strip that propagates along the line of the front and maintains a constant width in the direction perpendicular to the front. We observe the appearance of one or more small perturbations, which arise in a symmetric way. The influence of boundaries on the traveling waves was also investigated.

The Accumulation and Annealing of Radiation-Induced Defects and the Effect of Hydrogen on the Physicomechanical Properties of the V−4Ti−4Cr and V−10Ti−5Cr Vanadium-Based Alloys under Low-Temperature (at 77 K) Neutron Irradiation

The processes of the accumulation and annealing of radiation-induced defects that occur under low-temperature (at 77 K) irradiation (with an energy E > 0.1 MeV) of V−4Ti−4Cr and V−10Ti−5Cr bcc alloys both nonmodified and modified with hydrogen isotopes in a concentration of 200 ppm, as well as the effect of these processes on the physicomechanical properties of these alloys, have been studied. It has been found that the saturation of these alloys with hydrogen leads to slight changes in their strength and ductility characteristics. The irradiation of the alloys at the temperature of 77 K results in a substantial increase in their yield stress and ultimate strength, as well as a decrease in their ductility. In the course of the postradiation annealing of the alloys at a temperature of 130 K, the stage related to the migration of interstitial atoms is observed. At temperatures of 290–320 K, the recovery stage occurs due to the formation of vacancy clusters. The stage that occurs at a temperature of 470 K can be attributed to the formation of impurity-vacancy clusters. Possible mechanisms of the radiation-induced strengthening of the alloys during irradiation and subsequent annealing have been discussed.

On the processes upon the second-photon-stimulated annealing of InAs layers implanted with Be+ ions

The results of the second-photon-stimulated annealing of beryllium-implanted InAs layers are presented. The hole and electron concentrations and the activation energy of second-photon-stimulated annealing are calculated for the characteristic temperature regions using thermopower voltage values measured for the implanted layer. The possible mechanisms of the annealing of radiation-induced defects and the activation of beryllium atoms are discussed.

Annealing of radiation-induced damage in tungsten under and after irradiation with 20 MeV self-ions

Accumulation and recovery of radiation defects under/after self-ion irradiation in tungsten (W) have been investigated via decoration with deuterium (D) and scanning transmission electron microscopy (STEM). The deuterium was incorporated in damaged material by low-energy D plasma. The D concentration at radiation-induced defects in each sample was subsequently measured by nuclear reaction analysis allowing determination of the D concentration at depths up to 6μm. The total D retention was measured by thermal desorption spectroscopy. It was shown that pre-irradiation with self-ions led to rather high D concentration (⩾ 0.1at.%) in W even at high temperatures (⩾ 700K) due to formation of defects with high de-trapping energy for deuterium. The annealing of defects with low trapping energy for D occurs intensively in the temperature range between 300 and 700K. The radiation-induced defects with high de-trapping energy for D are thermally stable at least up to 1100K. The rearrangement and partial healing of dislocations as well as coalescence of small clusters in a big ones accompanied by a reduction of the total density of defects was observed by STEM after annealing of radiation-induced defects in recrystallized tungsten at 1000K. The D retention monotonically decreases in recrystallized W with increasing of annealing temperature up to 1100K that is in agreement with the reduction of radiation defect density observed by STEM. However, an increase of the D retention in ‘as received’ W pre-irradiated with self-ions at annealing temperature of around 1000K was found. The increase of the D retention at annealing temperature of ∼1000K was not observed in the case of recrystallized W pre-irradiated with self-ions. The mechanism of recovery of radiation-induced defects in dependence on the initial intrinsic defects (grain size, impurities, etc.) in W is discussed.

Estimating the Activation Enthalpy for Defect Formation in 5754 Alloys by Using Nuclear, Electrical and Mechanical Methods

The Positron Annihilation Lifetime Technique (PALT) Is One of the Most Important Nuclear Non-Destructive Techniques. it Was Used to Study the Activation Enthalpy for Defect Formation in 5754 Alloy. Quenching Experiments Were Usually Performed on Thin Specimens to Ensure a Uniform Quenching Rate throughout the Specimen. from such Measurements, it Is Possible to Deduce the Vacancy Formation Enthalpy which, in Combination with the Results of Self-Diffusion Measurements, Gives a Value for the Migration Enthalpy of the Vacancy. these Are Very Important Quantities in the Study of the Annealing of Irradiation-Induced Defects. the Use of the Quenching Technique in the Positron Annihilation Study Has the Advantage that it Allows a Distinction to Be Made between Vacancies and Dislocations. Correlations between Nuclear, Electrical and Mechanical Methods Have Been Carried Out after Quenching.

Radiation-induced modification of titanium nickelide with fast neutrons

We present a review of the investigations of the effect of fast neutrons on the structure and properties of titanium nickelide that were performed by the authors on an IVV-2M atomic reactor (Zarechnyi). It has been established that at small fluences of fast neutrons atomic disordering of crystals is observed; as the fluence increases, the material becomes partially amorphized; and at fluences higher than 1 × 1020 cm−2, the material transforms completely into the amorphous state. It has been shown that the amorphous state produced by neutron irradiation differs substantially from the amorphous state of materials obtained by conventional methods. In particular, if a single-crystal specimen is subjected to “neutron” amorphization (most of the investigations were carried out using single crystals), after annealing of radiation-induced defects the single crystal is restored with the initial orientation and perfection. The structural studies were conducted by the methods of neutron and X-ray diffraction. Based on these studies, as well as on the results of small-angle neutron scattering and dilatometric and resistivity measurements, the “defect” state of irradiated materials has been examined in detail. The radiation resistance of titanium nickelide has been estimated.

Annealing of radiation-induced defects in silicon

Annealing of the main radiation defects in silicon (A-centers, E-centers, and divacancies, etc.) is theoretically described on the basis of the experimental data obtained by many authors. The parameters that characterize this process (the activation energies and frequency factors) have been ascertained, and various mechanisms and reactions that determine the conditions for the annealing of the defects were proposed.

Annealing of radiation-induced defects in burn-in stressed power VDMOSFETs

The annealing of radiation-induced defects in burn-in stressed n-channel power VDMOSFETs with thick gate oxides (100 and 120 nm) is analysed. In comparison with the previous spontaneous recovery, the changes of device electrical parameters observed during annealing are highlighted by the elevated temperature and voltage applied to the gate, and are more pronounced in devices with a 120 nm thick gate oxide. The threshold voltage of VDMOSFETs with a 100 nm thick gate oxide during annealing has an initially slow growth, but then increases rapidly and reaches the value higher than the pre-irradiation one (rebound effect). In the case of devices with a 120 nm thick gate oxide, the threshold voltage behaviour also consists of a slight initial increase followed by a rapid, but dilatory increase, with an obvious tendency to achieve the rebound. The changes of channel carrier mobility during annealing are similar in all samples: at first, it slowly and then rapidly declines, and after reaching the minimum it begins to increase. In the case of VDMOSFETs with a thicker gate oxide, these changes are much slower. The underlying changes in the densities of gate oxide-trapped charge and interface traps are also delayed in devices with a thicker gate oxide. All these phenomena occur with certain delay in burn-in stressed devices compared to unstressed ones. The leading role in the mechanisms responsible for the observed phenomena is attributed to hydrogen related species.

Effect of high-temperature heat treatment on the generation and annealing of radiation-induced defects in n-type silicon crystals

Defect formation and annealing processes in n-type silicon crystals heat-treated at temperatures from 550 to 1000°C for a short time and then gamma-irradiated in a 60Co source or electron-irradiated (E = 4 MeV) at room temperature have been studied using Hall effect measurements. The results demonstrate that the preheat treatment (PHT) has an insignificant effect on the energy spectrum and generation efficiency of major defect species. At the same time, PHT results in enhanced annealing of radiation-induced defects, accompanied by the formation of additional electrically active centers. PHT is assumed to activate transition-metal impurities (fast diffusers in silicon), which then interact with radiation-induced defects.

Annealing of radiation-induced defects in n-GaAs

A change in the charge state of defects may give rise to a change in probability of their interactions, migration activation energy and stability of the systems, which might become evident during annealing of defects. Since the level of semiconductor doping, the type of conduction, and the presence of embedded and external electrical fields control the charge state of defects, all these would affect their thermal stability. Dislocations, clusters of basic elements in compound semiconductors, zones of disordering in semiconductors irradiated by neutrons, and devices with the p–n-transitions and Schottky barriers are sources of the space charge regions (SCRs). The presence of a neutral volume (NV) and an SCR and, hence, a different position of the Fermi level with respect to the level of “deeper” defects causes differences in their charge states in these regions. This might give rise to a situation where the formation and annealing of defects in an SCR would differ from those in an NV [1]. The purpose of this work is to study the effect of the charge state of radiation-induced defects in n-GaAs on their annealing [1]. The specimens under study were Schottky diodes manufactured from an epitaxial film grown by a gas-phase method on a highly doped substrate. The concentration of free carriers in the film was (1–5)⋅10 cm. Irradiation of the specimens by γ-quanta from a Co source and by 10 MeV protons was performed at room temperature. The flux and fluence of the γ-quanta were I = 9.4⋅10 quant/(cm⋅с), D = 2.6⋅10 quant/cm, respectively. Irradiation by the protons was performed at I = 3.5⋅10 proton/cm⋅с and D = 4⋅10 proton/cm. Defect concentration was measured by the method of deep level transient spectroscopy (DLTS). In order to study the effect of the defect charge state, comparison was made of the results of specimen annealing with (in SCR) and without (in NV) application of a back bias voltage. Shown in Fig. 1 are the curves of isothermal annealing of E3 centers in gallium arsenide irradiated by γ-quanta. It is evident that the concentration logarithm of these centers is a linear function of annealing time, which testifies to the fact that the annealing reaction order η = 1. The annealing activation energy E and the frequency factor ν, determined by the method of sectioning [2] of the isotherms from Fig. 1a, agree with the literature data [3] and are equal to (1.5 ± 0.05) eV and 10 s, respectively. The parameters of annealing of E3 centers in an SCR were found from the data shown in Fig. 1b to be as follows: E = (1.6–1.8) eV, η = 1, and ν ≈ 10 s. These results demonstrate that the E3 annealing rate in an SCR is lower that that in an NV. Presented in Fig. 2 are the curves of isochronous annealing of E2 and E3 centers in NVs and SCRs of gallium arsenide irradiated by γ-quanta. It is evident from Fig. 2a that the thermal stability of E2 centers in NVs and SCRs is the same, while that of E3 in SCRs is higher than it is in NVs. Figure 2b depicts the curves of isochronous annealing of E5 centers in NVs and SCRs, which are qualitatively similar to those of annealing of E3 enters. These data demonstrate that E5, as well as E3 centers in SCRs are annealed much slower than in NVs of gallium arsenide irradiated by γ-quanta. The parameters of annealing of E5 centers in NVs and SCRs were estimated from the curves of isothermal annealing to be as follows: E = (1.5 ± 0.05) eV, ν ≈ 10 s and E = (1.7 ± 0.1) eV, ν ≈ 10 s, respectively. Thus, the annealing kinetics for E5 coincides with that for E3 centers both in NVs and SCRs. An examination was made of the “back bias/no back bias” cycle on the character of annealing of defects in NVs and SCRs at Т = 493 K for E3 center (Fig. 3). Curve 1 was obtained at U = 0, Curve 2 was constructed with alternated application of U = 30 V (sections b, d, f) and without its application (sections a, c, e) in the course of annealing. It is evident from the figure that sections a, c, e are parallel to curve 1. This implies that the kinetics of subsequent annealing in sections a, c, e (U = 0) after the preceding annealing run at U = 30 V is reversibly returned to the annealing kinetics in NVs and is characterized by the same parameters as the process in curve 1: E = 1.5 eV, η = 1, and ν ≈ 10 s.

Investigation of radiation-induced defects in the electron irradiated power transistor structures

The formation and annealing of radiation-induced defects in n-collector of power silicon transistor structures irradiated with fast electrons (E=4MeV) have been studied. It is found that the main stage of recovery of the minority carrier lifetime in the transistor collector region upon isochronal annealing occurs at temperatures corresponding to the disappearance of the vacancy–oxygen complex.

Evaluation of techniques for characterizing virgin and γ-irradiated power VDMOSFETs

There is a continued interest in hardening devices against irradiation which encounter harsh radiation environment. Charge buildup and generation of interface states are the most important degradation factors in VDMOSFETs. They may occur in the course of device fabrication or later during device operation causing reliability problems. Split C–V, charge pumping and subthreshold slope-midgap techniques were applied for understanding the mechanisms that lead to both buildup and annealing of irradiation-induced defects. This is necessary due to the assessment and improvement of the response of devices in an ionizing radiation environment. The results obtained by cited methods are compared to propound their advantages and drawbacks.

Annealing of radiation-induced defects in silicon in a simplified phenomenological model

The concentration of primary radiation-induced defects has been previously estimated considering both the explicit mechanisms of the primary interaction between the incoming particle and the nuclei of the semiconductor lattice, and the recoil energy partition between ionisation and displacements, in the frame of the Lindhard theory. The primary displacement defects are vacancies and interstitials that are essentially unstable in silicon. They interact via migration, recombination, annihilation or produce other defects. In the present work, the time evolution of the concentration of defects induced by pions in medium and high resistivity silicon for detectors is modelled, after irradiation. In some approximations, the differential equations representing the time evolution processes could be decoupled. The theoretical equations so obtained are solved analytically in some particular cases, with one free parameter, for a wide range of particle fluences and/or for a wide energy range of incident particles, for different temperatures; the corresponding stationary solutions are also presented.

Behavior of electrically active point defects in irradiated MOCVD n-GaN

Formation and annealing of radiation-induced defects in doped and nominally undoped n-GaN are investigated by means of electrical measurements and Raman spectroscopy. The production rate of defects turned out to be dependent on the dopant concentration. This suggests that at least one kind of native defects is involved in impurity–defect interactions at room temperature. Two prominent stages of defect annealing are revealed. The annealing processes at T≥100°C are associated with mobile native defects. A considerable fraction of radiation defects is still present in the materials after annealing to T≥750°C.

Bias-dependent annealing of radiation damage in neutron-irradiated silicon p +-n-n + diodes

Silicon pad diodes fabricated on n-type substrates were irradiated with fast neutrons from the TRIGA reactor facility to fluences around 5×10 13 n/cm 2. Annealing of radiation-induced defects was monitored via the full depletion voltage (FDV) obtained from C– V measurements, both during and after irradiation. As much as 50% difference in FDV was observed to appear between biased and unbiased diodes in a few hours after irradiation, with the biased diodes having the higher value. The FDV difference persists through later stages of annealing and reverse annealing. Upon switching off the bias voltage, the difference in FDV diminishes within days at room temperature. Observation of different effective dopant concentrations within the same detector in regions with and without electric field provides further evidence for bias-dependent annealing. No bias effect is seen on the reverse-current annealing.

Annealing of radiation-induced defects in vanadium and vanadium-titanium alloys

The annealing of defects induced by electron irradiation up to a dose of 6 × 10 21 m −2 at T < 293K has been investigated in single-crystals of pure vanadium and in vanadium-titanium alloys with compositions 0.3, 1 and 5 at.% Ti using positron annihilation spectroscopy. The recovery of the positron annihilation parameters in V single-crystals indicates that the defect annealing takes place in the temperature range 410–470 K without formation of microvoids for the present irradiation conditions. For the alloys the recovery onset is shifted to 460 K, the width of the annealing stage is gradually broadened with increasing Ti content, and microvoids are formed for annealing temperatures at the end of the recovery stage. The results show that the vacancy release from vacancy-interstitial impurity pairs and subsequent recombination with interstitial loops is the mechanism of the recovery in pure V. For V-Ti alloys, vacancy-Ti-interstitial impurity complexes and vacancy-Ti pairs appear to be the defects responsible for the positron trapping. The broadening of teh recovery stage with increasing Ti content indicates that solute Ti is a very effective trap for vacancies in V.

Elevated Temperature Implantation of GaAs With Si Ions

AbstbactThe formation of amnorphous layers in GaAs during ion bombardment at elevated temperatures, where dynamic annealing of radiation-induced defects is substantial, is shown to be extremely sensitive to the ion flux. fluence. and implantation temperature. For example. with increasing fluence. damage can first build up extremely slowly. then suddenly collapse to the amorphous phase. Alternatively. for a constant ion fluence, a change in flux by one order of magnitude can change the critical temperature for amorphisation by 27°C. and at constant flux and fluence. a change of only 6°C can alter the residual damage from small clusters barely visible by conventional transmission electron microscopy and Rutherlord backscattering to a thick amorphous layer. The temperature at which this occurs is strongly dependent upon the ion flux and fluence.

Elevated Temperature Implantation of GaAs with Si Ions.

AbstractThe formation of amorphous layers in GaAs during ion bombardment at elevated temperatures, where dynamic annealing of radiation-induced defects is substantial, is shown to be extremely sensitive to the ion flux, fluence, and implantation temperature. For example, with increasing fluence, damage can first build up extremely slowly, then suddenly collapse to the amorphous phase. Alternatively, for a constant ion fluence, a change in flux by one order of magnitude can change the critical temperature for amorphisation by 27°C, and at constant flux and fluence, a change of only 6°C can alter the residual damage from small clusters barely visible by conventional transmission electron microscopy and Rutherford backscattering to a thick amorphous layer. The temperature at which this occurs is strongly dependent upon the ion flux and fluence.