MeV Electron Irradiation Research Articles

Degradation analysis of 3J InGaP/InGaAs/InGaAsN solar cell due to irradiation induced defects with a comparative study on bottom homo and hetero InGaAsN subcell

The influence of irradiation induced traps in the triple junction In0.49Ga0.51P/In0.01Ga0.99As/In0.30Ga0.70As0.98N0.02 solar cell was studied using finite element analysis. The total 3J solar cell structure was simulated separately with homo and hetero InGaAsN structure as the third or bottom subcell. The higher efficient 3J InGaP/InGaAs/InGaAsN solar cell with bottom InGaAsN heterostructure was analyzed by including irradiation induced trap levels. The trap levels correspond to 1 MeV electron irradiation with fluence range of 1 × 1014–1 × 1016 in electrons/cm2 at room temperature. We realized that the traps in the middle cell cause more degradation, followed by bottom cell and then top cell. The onset of degradation of solar cell parameters (Jsc, Voc and η) starts at trap concentration 1 × 1013 cm−3, while more degradation occurs beyond 1 × 1016 cm−3. At trap concentration of 1 × 1016 cm−3, the solar cell design was optimized for achieving current matching among the subcells. While we obtained 36% conversion efficiency at 1-sun (AM0 spectrum) using bottom heterostructure, the introduction of 1 × 1016 cm−3 trap concentration and 104 cm/s surface recombination velocity simultaneously in all subcells resulted in 20.8% conversion efficiency which increased to 24.3% after current matching.

Function composites materials for shielding applications: Correlation between phase separation and attenuation properties

The problem of increasing reliability of semiconductor devices under extreme ionizing radiation (electrons, protons, gamma radiation etc.) is relevant. Uses of WCu composite materials with high density and reduced mass-dimension characteristics offer a very attractive alternative to lead protection due to more environmentally friendly composite. W85Cu15 and W75Cu25 composites were obtained by solid-phase synthesis. XRD data showed that the main lines of the WCu spectrum correspond to the body-centered cubic phase of tungsten-copper alloy and the face-centered cubic phase of copper. The W85Cu15 and W75Cu25 composites consist two main phases: W0,6Cu0,4 phase and Cu phase. This may be due to the alloy presence on the outer part of the tungsten grains, which was formed as a result of thermal annealing and copper diffusion during composite synthesis. The most intense peak (110) is maintained when the tungsten concentration changes. The peaks shift towards large angles with a tungsten concentration decreasing in the composite is observed. The intensity of copper peaks increases and a new low-intensity peak appears (220) with the copper concentration increasing in the composite. The shielding properties of the W85Cu15 composite with n- and p-MOS transistors under 1.6÷1.8 MeV electron radiation have been studied. It has been established that maximum shielding efficiency for p-MOS transistors (Ka = 143÷155) have shields with 1.2÷1.5 mm thickness. Shields provide the total absorbed dose reduction up to 6 times for outer space protons (energies from 0.04 to 500 MeV for the 60° orbital inclination and a circular orbit with a height of 300 km).

Temperature-dependent photoluminescence processes of GaInP top cell irradiated with 11.5 MeV and 1.0 MeV electrons

The effects of 11.5 MeV electrons irradiation on the GaInP top cell of GaInP/GaAs/Ge triple-junction solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements. The thermal quenching of PL intensity is observed in the temperature range of 10 K–270 K, attributing to the nonradiative recombination centers H2 (Ev + 0.55 eV) hole trap and H3 (Ev + 0.76 eV) hole trap. A slight negative thermal quenching (NTQ) of PL intensity exists at nearly 300 K and could be associated with the 0.18 eV intermediate states. The temperature-dependent photoluminescence process of GaInP top cell irradiated with 11.5 MeV electrons differs with that irradiated with 1.0 MeV electrons.

Protective Effects of Magnesium Sulfate on Radiation Induced Brain Injury in Rats.

The effect of magnesium sulfate on brain tissue of SD rats irradiated by 6MeV electron was investigated. SD rats were divided into three groups: control group, irradiation (IR group) and irradiation treated with magnesium sulfate (IR+M group). After being anesthetized, the whole brains of IR group and IR+M group were exposed to 6 MeV electron radiation. IR+M group was i.p. injected with 10% magnesium sulfate (400 mg/kg) one day before radiation and three days and five days after radiation. And on the 1st, 3rd, 7th and 14th day after radiation, SD rats were euthanatized to take brain tissue for the detection of calcium, redox status and cell apoptosis, as well as the expression of NF-κB and ICAM-1. The results indicated that magnesium treatment may alleviate the elevation of calcium and enhance redox status through increasing the activities of superoxide dimutase (SOD) and myeloperodase (MPO), and decreasing the concentration of malondialdehyde (MDA). Tunnel and immunohistochemistry assay suggested that treatment with magnesium decreased the apoptosis rate of brain cells and the expressions of caspase-3, respectively. Decline of the expression of NF-κB and ICAM-1 protein was observed after the treatment of magnesium. All the results demonstrated that magnesium may elicit protective effect against radiationinduced brain injury by reducing calcium overload, improving redox and inhibiting cell apoptosis. Moreover, magnesium significantly down-regulated the protein or mRNA levels of NF-κB and ICAM- 1. The findings may provide references for the application of magnesium in clinic for brain injury induced by radiation.

Time resolved photoluminescence studies of degradation in GaInP/GaAs/Ge solar cells after 1MeV electron irradiation

Time resolved photoluminescence (TRPL) is a powerful method to character the behaviors of carriers as it has high time resolution that could reflect the reactions of carriers within nanoseconds. For solar cells, minority carrier lifetime is the most important parameter. TRPL has been used to measure the lifetime for uniform materials. However, for homojunction solar cells, doping distribution and carrier drift make the spectroscopy analysis much difficult. Thus one dimension numerical calculations are used to study the time-dependent photoluminescence (TRPL) decay of GaAs sub-cell in GaInP/GaAs/Ge solar cells. Calculation shows that both lifetime of minorities and light intensities could determine the line shape of TRPL. The bimolecular recombination under high injection modifies the curve from single-exponential to non-single-exponential one. For TRPL of homojunction solar cell, the photoluminescence decay process is not synchronized in all parts, and the decay is fast in emitter but slower in base regions. To get the lifetimes of minority carriers after 1MeV electron irradiation, carrier generation parameter G0 should be fitted by numerical method firstly. The damage factor Kτ=4.8×10-15 cm2/ns is fitted from TRPL results. Photoluminescence spectra (PL) are also used to get Kτ=5.5×10-15 cm2/ns which is similar with the value obtained from TRPL.

Optical and spin coherence properties of NV center in diamond and 3C-SiC

We investigated the optical properties and electronic structure of NV−1 center in diamond and 3C-SiC by combing photoluminescence spectroscopy (PL) and first-principles calculations. The NV−1 center in diamond and 3C-SiC were produced by 10 MeV electrons irradiation and 1 MeV silicon ions implantation at room temperature, respectively. We observed the zero phonon line (ZPL) of NV−1 center in 3C-SiC for the first time, which was different from that in diamond. The NV−1 centers in both host materials have the same configuration, which possess different spin-conserved optical transition energy. This phenomenon was interpreted by electronic structure and density of state calculations. Moreover, a long spin coherence time of NV−1 center in 3C-SiC was predicted by combining first-principles calculations and a mean-field theory for spin hyperfine interaction.

Effects of 10 MeV electron irradiation on the characteristics of gallium-nitride-based pin alpha-particle detectors

GaN-based pin alpha-particle detectors grown on sapphire substrates have been subjected to 10 MeV electron irradiation over a cumulative dose range of 0 to 200 kGy. The pre- and post-irradiation detectors have been characterized with current–voltage and capacitance–voltage measurements, charge collection efficiency (CCE), and alpha-particle pulse-height spectroscopy. The results show that the performance of the detectors underwent significant changes due to enhanced carrier-hopping conductivity through defect states and deep-level traps in the space-charge region induced by the 10 MeV electron irradiation. Such detectors can be used for alpha detection with confidence in an environment of background high energy electrons, up to a dose of about 200 kGy, and the response can degrade rapidly if the dose exceeds 200 kGy. In this work, the maximum CCE was achieved in a detectors irradiated with a cumulative dose of 100 kGy.

Hydrogen Soaking, Displacement Damage Effects, and Charge Yield in Gated Lateral Bipolar Junction Transistors

The effects of 70-keV and 1-MeV electron irradiations on gate-controlled lateral PNP (GLPNP) transistors are evaluated with and without molecular hydrogen (H2) soaking. At a given ionization dose, 1-MeV electron irradiation causes more degradation of current gain in GLPNP transistors that have not been soaked in H2 than 70-keV electrons. This is because linear bipolar transistors are sensitive to both ionization and displacement damage effects, and because 1-MeV electrons induce significant displacement damage in Si-based bipolar junction transistors and 70-keV electrons do not. In H2-soaked transistors, the degradation is much larger than in unsoaked devices, and similar amounts of degradation are observed for 70-keV electron irradiation and 1-MeV electron irradiation. This occurs because ionization–induced release, transport, and reactions of hydrogen in the bipolar-base oxide greatly enhance interface-trap buildup and dominate device response in H2-soaked devices, and because charge yield ratios for 70-keV and 1-MeV electron irradiations differ by less than ~20%.

External quantum efficiency artifacts in partial‐irradiated GaInP/GaAs/Ge solar cells by protons and electrons

AbstractArtifact is a special kind of phenomenon related to fluorescence coupling and shunt resistance in external quantum efficiency (EQE) measurements in multijunction (MJ) solar cells, and it is sensitive to the defects and damages. In this paper, the changes of artifacts were studied in partial irradiated MJ solar cells by common or two‐dimension mapping Quantum Efficiency (QE) measurements. Simplified mathematical models and graphic analysis were applied to explain the mechanisms of changes of artifacts. Irradiation weakens the artifacts effects due to the decrease in relative fluorescence yield. Artifacts analysis results indicate that after 1 MeV electron irradiation, the open circuit voltage Voc of GaInP subcell decays from 1.40 V to 1.35 V, and the reverse saturation non‐radiative recombination current I02 increases 3.7 times. Correspondingly, after 70 keV protons irradiation, the open circuit voltage Voc decays to 0.90 V and I02 increases 7550 times by EQE artifacts analysis. Lateral scanning of the partial damaged samples shows a smooth artifacts transition region that appears near the boundary of damaged region in MJ solar cells. This is found correlated with the difference in the lighted areas of bias light and EQE pulse spot. 2D artifacts analysis could properly explain the smoothness and shift of damage interface.

Influence of 20 MeV electron irradiation on the optical properties and phase composition of SiOx thin films

Homogeneous films from SiO1.3 (250 nm thick) were deposited on crystalline Si substrates by thermal evaporation of silicon monoxide. A part of the films was further annealed at 700 °C to grow amorphous Si (a-Si) nanoclusters in an oxide matrix, thus producing composite a-Si-SiO1.8 films. Homogeneous as well as composite films were irradiated by 20-MeV electrons at fluences of 7.2 × 1014 and 1.44 × 1015 el/cm2. The film thicknesses and optical constants were explored by spectroscopic ellipsometry. The development of the phase composition of the films caused by the electron-beam irradiation was studied by transmission electron microscopy. The ellipsometric and electron microscopy results have shown that the SiOx films are optically homogeneous and the electron irradiation with a fluence of 7.2 × 1014 el/cm2 has led to small changes in the optical constants and the formation of very small a-Si nanoclusters. The irradiation of the a-Si-SiOx composite films caused a decrease in the effective refractive index and, at the same time, an increase in the refractive index of the oxide matrix. Irradiation induced increase in the optical band gap and decrease in the absorption coefficient of the thermally grown amorphous Si nanoclusters have also been observed. The obtained results are discussed in terms of the formation of small amorphous silicon nanoclusters in the homogeneous layers and electron irradiation induced reduction in the nanocluster size in the composite films. The conclusion for the nanoparticle size reduction is supported by infrared transmittance results.

Effect of Si concentration on formation of vacancy complexes in electron-irradiated Fe16Cr-Si alloys studied by positron annihilation

The effect of Si concentration (0.2, 0.75 and 1.5 at.%) on properties of vacancy type defects formed under 5 MeV electron irradiation near 300 K in Fe-16 at.% Cr matrix has been studied by means of angular correlation of annihilation radiation technique. It is found that vacancy clusters are accumulated in Fe16Cr and Fe16Cr-0.2Si. Accumulation of monovacancies and their decoration with Si atoms are observed in Fe16Cr-1.5Si. Accumulation in Fe16Cr-0.75Si demonstrates transient features. Post-irradiation annealing kinetics in Fe16Cr and Fe16Cr-0.2Si differs from that in Fe16Cr-0.75Si and Fe16Cr-1.5Si. Annealing of vacancy clusters takes place in Fe16Cr and Fe16Cr-0.2Si, while vacancy clusters form and start annealing in Fe16Cr-0.75Si and Fe16Cr-1.5Si above 425 K. It is concluded that Si atoms aggregates are formed in Fe16Cr- 0.75Si and Fe16Cr-1.5Si under irradiation, which capture monovacancies and hold them up to 425 K. Mechanism of Si aggregate formation is discussed based on published data on interaction between vacancies and atoms of Si in Fe-Si alloys.

Eighteen mega-electron-volt alpha-particle damage in homoepitaxial β-Ga2O3 Schottky rectifiers

Homoepitaxial Ga2O3 rectifiers with vertical geometry were subject to 18 MeV alpha particle irradiation at fluences of 1012–1013 cm−2, simulating space radiation exposure. The range of these particles (∼80 μm) is much greater than the drift layer thickness in the structures (∼7 μm). The carrier removal rates were in the range of 406–728 cm−1 for these conditions. These values are factors of 2–3 higher than for high energy (10 MeV) protons and 2 orders of magnitude higher than for 1.5 MeV electron irradiation of the same material. The on-state resistance of the rectifiers is more degraded by alpha particle irradiation than either ideality factor or barrier height. The reverse breakdown voltage of the rectifiers increases with alpha particle dose as carriers in the drift region are removed by trapping into traps created by the radiation damage. The on/off ratio of the rectifiers was severely degraded by alpha particle-induced damage, but the reverse recovery characteristics were unaffected even by the highest dose, with values around ∼20 ns.

Phase change in CoTi2 induced by MeV electron irradiation

The phase change induced by MeV electron irradiation in the intermetallic compound E93–CoTi2 was investigated using high-voltage electron microscopy. Under MeV electron irradiation, CoTi2 was first transformed into an amorphous phase and, with continued irradiation, crystallite formation in the amorphous phase (i.e. formation of crystallites of a solid-solution phase within the amorphous phase) was induced. The critical temperature for amorphisation was around 250 K. The total dose (dpa) required for crystallite formation (i.e. that required for partial crystallisation) was high (i.e. 27–80 dpa) and, even after prolonged irradiation, the amorphous phase was retained in the irradiated sample. Such partial crystallisation behaviour of amorphous Co33Ti67 was clearly different from the crystallisation behaviour (i.e. amorphous-to-solid solution, polymorphous transformation) of amorphous Cr67Ti33 reported in the literature. A possible cause of the difference is discussed.

Robust s± pairing in CaK(Fe1−xNix)4As4 ( x=0 and 0.05) from the response to electron irradiation

Controlled point-like disorder introduced by 2.5 MeV electron irradiation was used to probe the superconducting state of single crystals of \CaKx\ superconductor at $x = 0$ and 0.05 doping levels. Both compositions show an increase of the residual resistivity and a decrease of the superconducting transition temperature, $T_c$ at the rate of $dT_c/d\rho(T_c) \approx$ 0.19 K(\textmu$\Omega$cm)$^{-1}$ for $x=0$ and 0.38 K(\textmu$\Omega$cm)$^{-1}$ for $x=\:$0.05, respectively. In Ni - doped, $x = 0.05$, compound the coexisting spin-vortex crystal (SVC) magnetic phase is suppressed at the rate of $dT_N/d\rho(T_N)\approx$ 0.16 K(\textmu$\Omega$cm)$^{-1}$. Low - temperature variation of London penetration depth is well approximated by the power law, $\Delta \lambda (T) = AT^n$ with $n\approx\,$2.5 for $x=0$ and $n\approx\,$1.9 for $x=0.05$ in the pristine state. Electron irradiation leads to the exponent $n$ increase above 2 in $x=0.05$ suggesting superconducting gap with significant anisotropy that is smeared by the disorder scattering. Detailed analysis of $\lambda (T)$ and \(T_{c}\) evolution with disorder is consistent with two effective nodeless superconducting energy gaps due to robust s$_{\pm}$ pairing. Overall the behavior of \CaKx\ at $x = 0$ is similar to a slightly overdoped \BaK\ at $y \approx$ 0.5 and at $x= 0.05$ to an underdoped composition at $y \approx$ 0.2.

Electron and Proton Irradiation Damage in β-Ga2O3 Vertical Rectifiers

Wide bandgap semiconductors materials have always been the interest of their ability that can withstand high radiation fluences for the military, nuclear-industry monitoring, satellites and other space-borne applications. Monoclinic β phase Ga2O3 is attracting great attention for power electronics and solar-blind photodetectors because of its large bandgap (~4.9 eV) and a critical electric field strength of 8 MV/cm.[1,2,3] Also, the large diameter bulk β- Ga2O3 is commercially available with a controllable n-type doping for its epitaxial layers. Given its high bond strength and expected high vacancy formation energy, β- Ga2O3 is likely to be very radiation hard based on the reduced density of atomic displacements expected for a given energy of non-ionizing radiation exposure.[4] The cosmic rays, trapped radiation in the Earth’s radiation belts, and solar particle events are three primary sources of space irradiation. The cosmic rays consist predominantly of protons; the radiation belts contain energetic protons and electrons while solar particle events are mostly lower energy protons and electrons, in which the average integral proton fluxes at 10 MeV are of order 1014 cm-2.[1] Thus, it is important to understand the effect of energetic proton irradiation on Ga2O3. For electron irradiation, vertical rectifiers fabricated on epi Ga2O3 (Si-doped, 10 μm) on bulk (001) β- Ga2O3 substrate (Sn-doped, 650 μm) with Ti/Au as the ohmic contact for the full back area and Ni/Au for Schottky contacts in the front. The rectifiers were subject to 1.5 MeV electron irradiation at fluences from 1.79 × 1015 to 1.43 × 1016 cm-2 at a fixed beam current of 10-3 A. The electron irradiation caused a reduction in carrier concentration in the epi Ga2O3, with a carrier removal rate of 4.9 cm-1. The electron-induced damage would cause the 2kT region of the forward current-voltage characteristics increase. For the highest electron fluence, the diode ideality factor increased around 8% along with two orders of magnitude increase in on-state resistance. There was a significant reduction in reverse bias current that scaled with electron fluence. The diode on/off ratio was measured when switching from +1 V to -40 V. At -10 V reverse bias voltage, the on/off ratio was severely degraded by electron irradiation, decreasing from ~107 in the reference diodes to ~2 × 103 for the 1.43 × 1016 cm-2 fluence. The reverse recovery characteristics showed little changes even at the highest fluence, with the reverse recovery time in the range 21-25 nsec for all rectifiers. This phenomenon can be explained by the short minority carrier lifetime. which controls the carrier storage time in Ga2O3 intrinsic layer.[3] Also, based on the diode on/off ratio, the primary cause of the degradation was introduced by the reduction of majority carrier concentration. Regarding proton irradiation, β- Ga2O3 vertical rectifiers were subject to 10 MeV proton irradiation at a fixed fluence of 1014 cm-2. The electrical performance of vertical rectifiers was measured before and after proton irradiation, as well as subsequent annealing up to 450°C. The carrier removal rate was determined to be 235.7 cm-1, which is comparable to the carrier removal rate for GaN-based heterostructures under the same proton energy. Point defects introduced by the proton damage create trap states that reduce the carrier concentration in the Ga2O3. Even annealing at 300°C produces a recovery of approximately half of the carriers in the Ga2O3, while annealing at 450°C almost restores the reverse breakdown voltage. The diode on/off ratio of the rectifiers switched from +1 V to -40 V. The diode on/off ratio was severely degraded by proton irradiation and this was only partially recovered by 450°C annealing. The minority carrier diffusion length decreased from ~340 nm for the reference diode to ~315 nm after the proton irradiation. R. Benton and E. V. Benton, Nucl. Instr. and Meth. in Phys. Res. B 184, 255 (2001).Higashiwaki, K. Sasaki, H. Murakami, Y. Kumagai, A. Koukitu, A. Kuramata, T. Masui and S. Yamakosh, Semicond. Sci. Technol., 31, 034001 (2016).Higashiwaki, K. Sasaki, A. Kuramata, T. Masui and S. Yamakoshi, Appl. Phys. Lett., 100, 013504 (2012).I. Stepanov, V.I. Nikolaev, V. E. Bougrov and A.E. Romanov, Rev. Adv. Mater. Sci., 44, 63 (2016). Figure 1

Mechanisms of 200 MeV electron radiation in diamond crystal in the axial orientation

Abstract The γ -radiation by electrons with the energy of ∼ 200 MeV in a 100 μ m-thick diamond crystal has been measured at the MAX-lab experimental facility, when the electrons are incident on the crystal along the 〈 100 〉 axis. In this case, the intensity of the -radiation with the energy ∼ 1–2 MeV is approximately 16 times higher than that in amorphous matter of the same thickness. Theoretical calculations based on the quasi-classical QED approximation are in good agreement with the experimental data. The analysis of the radiation mechanisms has shown that the main contribution to the radiation intensity resulted from electrons, moving in the above-barrier regime and at small angles to the crystal axis.

Degeneration and damage mechanism of epoxy-based shape memory polymer under 1 MeV electron irradiation

The degradation behaviors of epoxy-based shape memory polymer (SMP) after 1 MeV electron irradiation were investigated in the paper. It was founded that the shape fixity rate remained almost no changed at approximately 99.6% while the shape recovery rate decreased rapidly from its original 98.6% to 85.9% with increasing fluence up to 200 × 1014 cm−2, which could be owned to the partial cleavage of the crosslinked network of epoxy-based SMP after irradiation. Further research found that the irradiation-induced scissions of the crosslinked network took place as a result of the debonding of the weak aliphatic C-O and C-N groups.

Correlation of the synthesis conditions and microstructure for Bi-based electron shields production

The various ionizing radiations (electrons, protons, heavy charged particles, X-ray and gamma radiation) are the damaging factors for microelectronic products. The common used material for radiation protection is lead. Recently, Bi deposition has become an interest for the electrochemical community because of bismuth's unique electrical, physical and chemical properties. There is a limited number of authors dealing with Bi films onto metallic substrates by electrochemical deposition. The electrochemical deposition conditions and Bi coatings structure were examined. X-ray diffraction patterns for all samples were indexed to rhombohedral Bi. Coatings with a signified texture (012) are formed in electrolyte without additives. With gelatin adding the growth texture changes and the most intense reflex becomes (110). It was found that gelatin concentration increasing from 0.1 to 0.5 g/L leads Bi microstructural refinement from 4-20 μm to 50 nm-2 μm, respectively. The protection efficiency of shields based on Bi under 1,6–1,8 MeV electron radiation energy was measured. The electron beam attenuation efficiency was estimated by the changing of current-voltage characteristics of semiconductor test structures which were located behind the shields and without them. It has been determined that optimal protection effectiveness and mass-dimensional parameters have Bi shields with 2 g/cm2 reduced thickness and 156 attenuation coefficient.

THE INFLUENCE OF HIGH-ENERGY ELECTRONS IRRADIATION ON SURFACE OF n-GaP AND ON Au/n-GaP/Al SCHOTTKY BARRIER DIODE

We fabricated 25 Au/[Formula: see text]-GaP/Al Schottky devices and investigated the influence of high electron irradiation, which has 12[Formula: see text]MeV on the devices, at room temperature. The X-ray diffraction patterns, scanning electron microscopic images and Raman spectra of a gallium phosphide (GaP) semiconductor before and after electron irradiation have been analyzed. Furthermore, some electrical measurements of the devices were carried out through the current–voltage ([Formula: see text]–[Formula: see text]) and capacitance–voltage ([Formula: see text]–[Formula: see text]) measurements. From the [Formula: see text]–[Formula: see text] characteristics, experimental ideality factor [Formula: see text] and barrier height [Formula: see text] values of these Schottky diodes have been determined before and after irradiation, respectively. The results have also been analyzed statically, and a gauss distribution has been obtained. The built-in potential [Formula: see text], barrier height [Formula: see text], Fermi level [Formula: see text] and donor concentration [Formula: see text] values have been determined from the reverse bias [Formula: see text]–[Formula: see text] and [Formula: see text] curves of Au/[Formula: see text]-GaP/Al Schottky barrier diodes at 100[Formula: see text]kHz before and after 12[Formula: see text]MeV electron irradiation. Furthermore, we obtained the series resistance values of Au/[Formula: see text]-GaP/Al Schottky barrier diodes with the help of different methods. Experimental results confirmed that the electrical characterization of the device changed with the electron irradiation.

High-dose MeV electron irradiation of Si-SiO2 structures implanted with high doses Si+

The influence was studied of 22-MeV electron irradiation on Si-SiO2 structures implanted with high-fluence Si+ ions. Our earlier works demonstrated that Si redistribution is observed in Si+-ion-implanted Si-SiO2 structures (after MeV electron irradiation) only in the case when ion implantation is carried out with a higher fluence (1016 cm-2). We focused our attention on the interaction of high-dose MeV electron irradiation (6.0×1016 cm-2) with n-Si-SiO2 structures implanted with Si+ ions (fluence 5.4×1016 cm-2 of the same order magnitude). The redistribution of both oxygen and silicon atoms in the implanted Si-SiO2 samples after MeV electron irradiation was studied by Rutherford back-scattering (RBS) spectroscopy in combination with a channeling technique (RBS/C). Our results demonstrated that the redistribution of oxygen and silicon atoms in the implanted samples reaches saturation after these high doses of MeV electron irradiation. The transformation of amorphous SiO2 surface into crystalline Si nanostructures (after MeV electron irradiation) was evidenced by atomic force microscopy (AFM). Silicon nanocrystals are formed on the SiO2 surface after MeV electron irradiation. The shape and number of the Si nanocrystals on the SiO2 surface depend on the MeV electron irradiation, while their size increases with the dose. The mean Si nanocrystals height is 16-20 nm after irradiation with MeV electrons at the dose of 6.0×1016 cm-2.