Electron Irradiation Defects Research Articles

Effect of electron irradiation defects on the martensitic transformation characteristics and microstructure of Ni45Co5Mn37In13 alloys

Ni-Co-Mn-In based alloys with magnetically driven shape memory effect have shown its huge potential for applying as the intelligent driver in the spacecrafts. However, the numerous cosmic radiations, especially the electron irradiation with large penetration depth, could seriously harm its' serving stability. Herein, the Ni45Co5Mn37In13 alloys are exposed to the high energy electron irradiation with different fluence to study the phase transition behavior and microstructure evolution in the irradiation process. As a result, we reveal that the electron irradiation could induce dense crystal defects which not only reduce the transition temperature and thus retain the residual austenite in the martensitic matrix, but also destroy the continuity of martensitic laths and the atom arrangement in the twin boundaries. This work has important theoretical significance for understanding the electron irradiation's effect on the martensitic transformation and microstructure of Ni-Co-Mn-In alloys, and is conducive to expand martensitic transformation theory.

Electron Irradiation Effects and Defects Analysis of the Upright Metamorphic Four‐Junction (UMM4J) Solar Cells

Herein, 1‐MeV electron irradiation is conducted to the AlGaInP (1.89 eV)/AlInGaAs (1.45 eV)/InGaAs (1.14 eV)/Ge (0.67 eV) upright metamorphic four‐junction (UMM4J) solar cell and its upper three key subcells. Light IV (LIV), external quantum efficiency (EQE), and deep level transient spectroscopy (DLTS) measurements are implemented to analyze the degradation of electric properties and evolution of defects of the UMM4J solar cell. The LIV results illustrate that the short circuit current (Isc), open circuit voltage (Voc), and maximum power (Pmax) degrade as a function of the logarithmic change of the electron fluence. EQE curves confirm the excellent anti‐irradiation characteristic of the AlGaInP (1.89 eV) subcell. Three types of electron traps E1 (Ec–0.16 eV), E2 (Ec–0.47 eV), and E3 (Ec–0.55 eV) are detected in the AlGaInP subcell. Two types of hole traps H1 (Ev + 0.35 eV) and H2 (Ev + 0.70 eV) are discovered in the AlInGaAs subcell and two types of hole traps H3 (Ev + 0.05 eV) and H4 (Ev + 0.36 eV) are observed in the InGaAs subcell. Nonionizing energy loss (NIEL) of 1‐MeV electrons in are calculated via Screened Relativist method. The defect concentrations show an approximately linear relationship with the displacement dose.

Electron Irradiation Effects and Defects Analysis of the Inverted Metamorphic Four-Junction Solar Cells

The degradation of inverted metamorphic four-junction (GaInP/GaAs/In0.3Ga0.7As/In0.58Ga0.42As, IMM4J) solar cells irradiated by 1-MeV electrons was investigated via their spectral responses and the characterization of their electrical properties. As in the case of traditional three-junction (TJ) GaInP/GaAs/Ge solar cells, the electrical properties ( I sc, V oc, and P max) decrease with the logarithmic change of the electron fluence. The degradation of open-circuit voltage ( V oc) is slightly more pronounced than that of I sc in IMM4J solar cells because of the sum rule for V oc and the limit rule for I sc. The spectral response analysis showed that an In0.3Ga0.7As subcell was the most damaged subcell in the irradiated IMM4J solar cell, but an In0.58Ga0.42As subcell had the lowest initial short-circuit current density (Jsc), which was maintained throughout the irradiation test. We therefore focused on the In0.58Ga0.42As subcell. Deep-level transient spectroscopy (DLTS) experiments were realized to study emission and capture processes in two special full configurations of In0.58Ga0.42As and In0.3Ga0.7As subcells of the IMM4J solar cell. DLTS measurements reveal a dominant electron trap at 0.52 eV below the conduction band (Ec) of In0.58Ga0.42As, and the electron trap gradually evolved into Ec-0.46eV and Ec-0.58eV after 1-MeV electron irradiation. Based on the first-principles calculation, Ec-0.46 eV and Ec-0.58 eV can be assigned as ${\bf V}_{{\bf Ga}}^{\bf 0}/{\bf V}_{{\bf Ga}}^{{\rm{ - }}1}$ and ${\bf V}_{{\bf In}}^{\bf 0}/{\bf V}_{{\bf In}}^{{\bf - 1}}$ , respectively. However, only one shallow level Ec-0.03eV was observed within the bandgap of In0.3Ga0.7As after irradiation with DLTS detection. We summarize the issues faced for the space application of IMM4J solar cells by comparing the spectral responses of IMM3J, IMM4J, and TJ solar cells. Finally, the optimization of the design and fabrication of IMM solar cells are proposed.

Theoretical simulation of the degradation on GaAs sub-cell with different defects induced by 1MeV electron irradiation

The degradation on the GaAs sub-cell of GaInP/GaAs/Ge triple-junction solar cells caused by different types of defects induced by 1 MeV electron irradiation is studied by numerical simulation. The simulation model is introduced that includes geometric structure, material, doping concentration and electron irradiation defects. The degradation results of short-circuit current, open-circuit voltage, maximum power, conversion efficiency and external quantum efficiency versus different defects have been investigated, and the degradation mechanism is analyzed. The results show that when the defect concentration and carrier capture cross-section is the same, the related parameters degradation of GaAs sub-cell is more serious when the defect energy level is closed to the intrinsic Fermi energy level. Meanwhile, the degradation of related parameters induced by E2 (Ec-0.14 eV) and E5 (Ec-0.96 eV) defects are more serious than the degradation of related parameters induced by other defects. The research will provide a method to analyze the detailed degradation mechanism induced by electron irradiation and a reference to analyze the degradation of solar cells induced by space particles.

Correlation between electron-irradiation defects and applied stress in graphene: A molecular dynamics study

Molecular dynamics (MD) simulations are performed to study the correlation between electron irradiation defects and applied stress in graphene. The electron irradiation effect is introduced by the binary collision model in the MD simulation. By applying a tensile stress to graphene, the number of adatom-vacancy (AV) and Stone–Wales (SW) defects increase under electron irradiation, while the number of single-vacancy defects is not noticeably affected by the applied stress. Both the activation and formation energies of an AV defect and the activation energy of an SW defect decrease when a tensile stress is applied to graphene. Applying tensile stress also relaxes the compression stress associated with SW defect formation. These effects induced by the applied stress cause the increase in AV and SW defect formation under electron irradiation.

Correlation between electron irradiation defects and applied stress in carbon nanotubes: A molecular dynamics study

Molecular dynamics simulations have been performed to study the correlation between electron irradiation defects and applied stress in single-walled carbon nanotubes. The electron irradiation effect is modeled based on the Monte Carlo method using binary collision theory. The simulations show that the number of knock-on defects is not significantly affected by applied stress. Electron collision causes early stage defects such as bond breaking and punched-out atoms. The applied stresses become nonequilibrium and concentrates around the defect site. The biased stresses become driving forces and cause bond shifts and rotations, which results in the formation of pentagon–heptagon pairs and Stone–Wales defects.

Thermal Behavior of Electron Irradiation Defects in CZ-Si

Behavior of the irradiation defects after annealing in electron irradiation CZ-Si has been studied by Four-Point Probe Measurement, Fourier Transform Infrared Absorption Spectrometer (FTIR) and Optical Microscope. The resistivities of irradiated silicon would decline under annealed at 750°C, it is considered that the oxygen related defects which present donor state were produced after annealed.

Study on Behavior of Electron Irradiation Defects and Impurities of Czochralski Silicon with Annealing by Positron Annihilation

Positron annihilation lifetime experiments have been performed for B-doped p-type Czochralski silicon (CZ-Si) wafers irradiated at 300 K with 1 MeV electrons with fluences between 1014 and 1017 e/cm2. In order to examine the thermal behavior of defects having shorter lifetime than that of the bulk, isochronal annealing experiments were carried out from 300 K to 900 K. The measurements were performed at 100 K to improve the positron trapping rates for defects. It is found that components having longer lifetime than that of the bulk behave differently, and they comprise by thermal donors (TD) and divacancies (V2). The short-lifetime component observed in the present experiments is responsible for a complex defect with impure interstitial oxygen atoms, doped B atoms and vacancies. The short-lifetime defects change into vacancy-type defects and thermal donors in certain ranges of annealing temperatures.

Combined potential and spin impurity scattering in cuprates

We present a theory of combined nonmagnetic and magnetic impurity scattering in anisotropic superconductors accounting for the momentum-dependent impurity potential. Applying the model to the d-wave superconducting state, we obtain a quantitative agreement with the initial suppression of the critical temperature due to Zn and Ni substitutions as well as electron irradiation defects in the cuprates. We suggest, that the unequal pair-breaking effect of Zn and Ni may be related to a different nature of the magnetic moments induced by these impurities.

Identification of electron-irradiation defects in semi-insulating GaAs by normalized thermally stimulated current measurements

Primary defects induced by 1 MeV electron irradiation have been quantitatively studied in semi-insulating (SI) GaAs by using normalized thermally stimulated current spectroscopy, a new technique. Defects identical to (or similar to) those known in the thermally stimulated current literature as ${\mathrm{T}}_{6}^{\mathrm{*}}$(0.13neV), ${\mathrm{T}}_{5}$ (0.34 eV), and ${\mathrm{T}}_{4}$ (0.31 eV) are produced at rates 0.70, 0.08, and 0.23 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ , respectively; ${\mathrm{T}}_{5}$ is also a strong trap in unirradiated SI GaAs. The defects ${\mathrm{T}}_{6}^{\mathrm{*}}$ and ${\mathrm{T}}_{4}$ correspond closely to the irradiation-induced traps E2(0.14 eV) and E3(0.30 eV), studied extensively by deep-level transient spectroscopy and Hall-effect measurements and assigned to the As vacancy. We thus infer that traps ${\mathrm{T}}_{6}^{\mathrm{*}}$ and ${\mathrm{T}}_{4}$ (and probably also ${\mathrm{T}}_{5}$ ) in SI GaAs have As-vacancy character.

Local Vibrational Mode (LVM) Spectroscopy of Semiconductors

AbstractImpurities and defects with masses smaller than the masses of the host semiconductor crystal atoms typically exhibit vibrational frequencies well above the phonon frequency spectrum. These vibrational modes produce sharp spectral absorption features in the infrared. Because of their strong spatial localization these modes are not affected by neighboring impurities and/or defects with concentrations up to 1019 cm−3. This insensitivity is especially advantageous when the free carrier concentration must be reduced through the introduction of electron irradiation defects or when highly doped thin layers must be investigated. LVM spectroscopy with perturbations such as polarization of the probe light, uniaxial and hydrostatic stress, and isotope substitution has been highly successful in identifying the structure and composition of a large number of defect complexes. Hydrogen, in particular, forming a wide variety of complexes in elemental and compound semiconductors has been extensively studied with LVM spectroscopy. For example, it has been shown recently that nitrogen acceptors are hydrogen passivated in MOCVD grown ZnSe. Carbon and oxygen have been investigated in all major semiconductors with LVM spectroscopy. The extreme simplification of the spectrum of bond centered oxygen through isotope enrichment of several Ge crystals has been demonstrated. Additional recent investigations of importance to the currently much studied semiconductors will be reviewed.

Irradiation effects of flux pinning and Jc in high temperature superconductors

Abstract We have introduced neutron and electron irradiation defects in bulk YBCO melt-textured materials. The defects and their effect on the critical current density (Jc) have been examined. The enhancement of Jc is found to be heavily dependent on the type and energy of the beam as well as on the direction of the beam with respect to the crystal. Two types of defects have been identified in neutron irradiated YBCO by positron annihilation experiments. The large defects (∼ 20 A) correlate with the enhancement of Jc and are 103 times more effective in flux pinning than point defects.

A Hvem Study of the Electron Irradiated Defects in Nitrogen Doped FZ-Si Single Crystal

AbstractHigh voltage transmission electron microscope (JEM-1000) has been used to investigate the electron irradiated defects in in p-type FZ-Si and nitrogen doped p-type FZ-Si. It was found that when the irradiated conditions were the saie ,the irradiated defects were easier to be produced in the FZ-Si than in nitrogen doped FZ-Si in the temperature range 573-773 K. The defect density was higher in the foraer. The migration energy of the vacancies in the temperature range 573-773 K was 0.34 and 0.58 eV for FZ-Si and nitrogen doped FZ-Si respectively. It seems to indicate that there was some interaction between vacancies and nitrogen atoms in the nitrogen doped FZ-Si. The results proved that the nitrogen doped FZ-Si has excellent property against electron irradiation.

E.P.R. study of electron irradiation defects in the red molybdenum bronze of potassium K0.33MoO3

Defects induced by electron irradiation in the red molybdenum bronze of potassium K 0.33 MoO 3 have been studied by E.R.P. spectroscopy. Two main types of centers (A et B) have been observed. They both have been identified as unpaired 4d electrons localized on one molybdenum atom with interaction with two other ones. A very simple electronic model is proposed to explain qualitatively the main features of these two paramagnetic centers. Measurements of the spin-lattice relaxation time of defect A show a temperature variation much slower than expected from the standard theory. This unusual dependence (laws in T 3 or T 5 ) can be explained by an extended theory which takes into account the contributions of lattice vibrations at the defect sites Nous avons etudie par R.E.P. les defauts crees dans K 0.33 MoO 3 par irradiation aux electrons. Nous avons ainsi mis en evidence l'existence de deux types de defauts (A et B) presentant de nombreux points communs: tous deux sont constitues d'un electron 4d non apparie localise preferentiellement sur un atome de molybdene et couple beaucoup plus faiblement avec deux autres atomes de molybdene. Nous proposons un modele tres simple pour la structure electronique de ces centres paramagnetiques. Les mesures du temps de relaxation spin-reseau ont montre une dependance en temperature tres inhabituelle (lois en T 3 et T 5 ) qui peut etre expliquee en considerant un modele de phonons localises au voisinage du defaut

STUDY OF THE LATTICE DEFECTS IN NiAl BY POSITRON ANNIHILATION

The structural defects, quenching defects and electron-irradiation defects in the in-termetallic compounds NiAl have been studies with the positron annihilation technique. The recovery behaviour of quenching defects and irradiation defects have been inversti-gated. Two distinct recovery stages have been, found, one at about 280℃ and the other at about 500℃. The experimental results show that the low-temperature stage is due to the annealing out of the divacancies and the high-temperature stage is due to the annealing out of the vacancies; and the density of the conduction electrons at the vacancies and the lattice interstitial sites are nearly equal to each other, but the momentum of the conduction electrons at the vacancies is lower than that at the latties interstitialsites in NiAl.

The convergent effect of the annealing temperatures of electron irradiated defects in FZ silicon grown in hydrogen : Qin Guogang and Hua Zonglu. Solid St. Commun.53 (11) 975 (1985)

A third generation industrial high current ion implanter, Series III, has been produced for the uniform implantation of milliampere-beams with total acceleration voltages up to 200 kV. Magnetic analysis of the beam with initial acceleration voltages variable up to 40 kV is carried out in the accelerator terminal followed by post-acceleration across a single gap up to a maximum total acceleration voltage of 200 kV into a grounded processor chamber.The ion source is a Freeman type capable of delivering milliampere beams of most elements. The source feed materials for the three main ion species required by the semiconductor industry, i.e. B, P and As, can all be pumped by surfaces with temperatures down to liquid nitrogen temperature. Consequently large liquid nitrogen cryopump/traps are used as the primary pumping system with diffusion pumps having a secondary role for non-cryopumpable gases. Three stages of differential pumping are provided in the accelerator together with a 12″ pumping system for the processor.The large processor takes a maximum load of 108 2″ silicon wafers or 54 3″ silicon wafers. Mechanical scanning is used because of the need to maintain space charge neutralisation in the beam which rules out electrostatic scanning and also because of the need to distribute the heat dissipation over a large number of wafers in order to prevent an excessive temperature rise in the wafers during high dose implants (>1015ions/cm2). The carousel which carries the wafers is shaped so that the wafers pass through the beam in a straight line and at a constant speed. A stepper motor driven vane unit in the terminal controls the ion beam current. In order to achieve high implantation uniformities the processor dose control system controls the ratio ion current/carousel speed and therefore any small non-uniformities in the carousel rotation speed can be compensated by the vane unit.The various functions in the terminal are controlled from ground potential using fibre optics. The system is highly automated and unskilled operators can be used.

The convergent effect of the annealing temperatures of electron irradiated defects in FZ silicon grown in hydrogen

In comparison with electron irradiated Si grown in argon, the annealing temperatures of electron irradiated defects in Si grown in hydrogen decrease and convergent to a small temperature range. The annealing temperatures of most electron irradiated defects in n type and p type Si grown in hydrogen are reduced and converge to the temperature interval between 250–270°C and 180–200°C respectively. The possible- mechanism of convergent effect of the annealing temperatures is discussed.

Three kinds of hydrogen-related electron irradiated defects in silicon grown in hydrogen

We have identified three kinds of hydrogen-related (HR) irradiated defects in Si crystals grown in H atmosphere. They are located at 0.08eV and 0.20eV below the conduction band and 0.10eV above the valance band respectively. Because they have different annealing temperatures, they are not the different charged states of the same defect center but correspond to different centers.

Electron irradiation defects in InP

We present here a study of the effect of RT electron irradiation on both the electrical and optical properties of InP. We concentrate more on the case of p-InP, for which, unlike n-InP, large concentrations of compensating defects and majority carrier traps are created. The electrically active defects can be separated into three categories: hole traps as detected by DLTS, which anneal in the temperature range 50–200 °C with a charge state dependence, compensating defects which drift under the influence of an electric field, and compensating defects which exhibit no drift and are not annealed up to 190 °C. Further information on defect stability is gained from the recovery above 200 °C of the luminescence efficiency, severely degraded after irradiation, which may correspond to the annealing of the residual electrically active defects. Finally, the origin of the strong compensation is at least partially related to an interaction between dopant Zn acceptors with irradiation defects, as evidenced by a strong quenching of the band to acceptor photoluminescence emission after irradiation, which recovers also above 200 °C. However, surprisingly high temperatures (≈600°C) are necessary for an almost total recovery of the luminescence efficiency, which indicates a high stability of secondary defects.

Electron-irradiation defects inn-type GaAs

We have studied the production and annealing of defects produced by 1-MeV electron irradiation of $n$-type GaAs. Two of these defects lie at 0.15 and 0.31 eV from the conduction band, respectively; in addition, there is at least one acceptor much closer to the valence band. The carrier-removal rate depends upon sample purity but is independent of the irradiation flux. The removal rate is also highly dependent upon the position of the the Fermi level, an effect which is considered in some detail. At about 200\ifmmode^\circ\else\textdegree\fi{}C, the defects recover in two stages, with the respective recovery rates given by ${\ensuremath{\lambda}}_{1}\ensuremath{\simeq}3\ifmmode\times\else\texttimes\fi{}{10}^{8}\mathrm{exp}(\ensuremath{-}\frac{1.2}{\mathrm{kT}})$ and ${\ensuremath{\lambda}}_{2}\ensuremath{\simeq}1\ifmmode\times\else\texttimes\fi{}{10}^{12}\mathrm{exp}(\ensuremath{-}\frac{1.6}{\mathrm{kT}})$ where the energies are in eV; ${\ensuremath{\lambda}}_{2}$ is somewhat dependent upon sample purity. In the highest-purity samples a reverse recovery phenomenon sometimes occurs, on about the same scale as ${\ensuremath{\lambda}}_{1}$. We present models for the production and recovery which are consistent with most of these results, as well as with other data found in the literature. It is suggested that the activation energies found in ${\ensuremath{\lambda}}_{1}$ and ${\ensuremath{\lambda}}_{2}$ may well be dissociation energies, rather than motional energies. Although the observed defects cannot be specifically identified, it appears that the level at 0.31 eV is a donor, and that at 0.15 eV is an acceptor; however, these conclusions are not firm.