High-temperature Electron Irradiation Research Articles

Magnetic properties of red diamonds produced by high-temperature electron irradiation

The magnetization of crystalline red diamond bulk samples were investigated in the temperature range between 2 K and 125 K and with the applied maximal magnetic field of ±7 T. The investigated diamond samples are of Type Ib with a nitrogen content less than 200 ppm. Diamonds without any treatment display a yellow color and were transformed to red color after irradiation with 10 MeV electrons at T=900°C, in vacuum, owing to the formation of nitrogen-vacancy centers. Field dependent magnetization m(H) measurements for temperatures T ≲ 10 K show unusual hysteresis loops, which we interpret as consequence of the superposition of coexisting superconducting and paramagnetic regions present in the sample. Temperature dependence of the magnetization m(T) measured in the zero field and field cooled modus shows a paramagnetic behavior accompanied with an irreversibility for T ≲ 13 K, while at higher temperatures shows a diamagnetic behavior which is similar to undoped diamond. Coexistence of superconductivity and paramagnetism is established because both phenomena exist in the same temperature range and fits done to the m(H) using an equation based upon Bean model, support our conclusion. Room temperature confocal photoluminescence measurements were done on both yellow and red diamond, showing that in the red diamond the amount of neutral NV° and negative charged nitrogen-vacancy centers NV− have been significantly created. The transformation process from yellow to red diamond has mainly caused the alteration of the superparamagnetic regions into paramagnetic, while the superconducting contribution of the sample was less affected, according to the parameters obtained after we fitted the field dependent magnetization results.

Impact of high temperature electron irradiation on characteristics of power SiC Schottky diodes

Impact of high temperature electron irradiation on the characteristics of power silicon carbide-based semiconductor devices was studied for the first time. Commercial 4H–SiC integrated Schottky diodes (JBS) with blocking voltage of 1700 V were irradiated with 0.9 MeV electrons at temperatures from 23 to 5000С in the fluence range Φ from 1 × 1016 cm−2 to 1.3 × 1017 cm−2. It was shown that ruggedness of the diodes during high temperature (“hot”) irradiation significantly exceeds the ruggedness of diodes at room temperature (“cold”) irradiation. With an increase in the irradiation temperature from 23 to 500 °C, the change in the base resistance at a fluence of 1.3 × 1017 cm−2 decreases by 6 orders of magnitude. In the entire investigated range of irradiation temperatures and fluences, irradiation does not change the height of the metal-semiconductor barrier even at the maximum fluence Φ.

Role of the intensity of high-temperature electron irradiation in accumulation of vacancy-oxygen defects in Cz n-Si

Kinetics of accumulation of oxygen–vacancy complexes, which is the dominant radiation-induced structural defect in the monocrystalline n-type Czochralski (Cz) silicon was studied experimentally and theoretically for silicon samples irradiated with electron beam pulses of various intensities and energies at 360 °C. The irradiation intensity was shown to have no effect on oxygen–vacancy complexes formation at temperatures when the complexes were unstable, but the complexes annealing efficiency revealed significant dependence on the electron beam intensity. In contrast, the electron beam energy affected the formation rate of vacancies themselves and their complexes with oxygen, but it did not influence annealing properties of oxygen–vacancy complexes. It occurred that the complexes generated in silicon at room temperature could be annealed at 360 °C much faster if irradiated with the electron beam during annealing. The results suggested an important role of radiation-induced ionization of a silicon crystal in transformation of oxygen–vacancy complexes into even more loaded complexes.

Efficient conversion of nitrogen to nitrogen-vacancy centers in diamond particles with high-temperature electron irradiation

Fluorescent nanodiamonds containing negatively-charged nitrogen-vacancy (NV−) centers are promising for a wide range of applications, such as for sensing, as fluorescence biomarkers, or to hyperpolarize nuclear spins. NV− centers are formed from substitutional nitrogen (P1 centers) defects and vacancies in the diamond lattice. Maximizing the concentration of NVs is most beneficial, which justifies the search for methods with a high yield of conversion from P1 to NV−. We report here the characterization of surface cleaned fluorescent micro- and nanodiamonds, obtained by irradiation of commercial diamond powder with high-energy (10 MeV) electrons and simultaneous annealing at 800 ∘C. Using this technique and increasing the irradiation dose, we demonstrate the creation of NV− with up to 25% conversion yield. Finally, we monitor the creation of irradiation-induced spin-1 defects in microdiamond particles, which we associate with W16 and W33 centers, and investigate the effects of irradiation dose and particle size on the coherence time of NV−.

Formation of carbon nanostructures in nuclear graphite under high-temperature in situ electron-irradiation

Defect evolution in nuclear graphite has been studied in real time using high-temperature in situ transmission electron microscopy. In situ electron-irradiation was conducted at 800 °C on a 200 kV transmission electron microscope with a dose rate, given in terms of displacements per atom per second, of approximately 1.46 × 10−3 dpa/s. Defect domains consisting of ordered arrangements of pentagons, hexagons, and heptagons exist intrinsically in nuclear graphite and in addition are readily produced via electron-irradiation; however, at elevated temperatures these defect domains undergo atomic rearrangements resulting in the formation of carbon nanostructures via curling and closure of the basal planes. The formation of fullerenes and other structures due to thermal annealing or high-temperature electron-irradiation has been observed in disordered regions of the microstructure and interstitially between basal planes. These defect structures result in localized swelling and expansion of crystallites along the c axis; thus, it is proposed as one of the many atomic mechanisms involved in the dimensional change of nuclear graphite subjected to high-temperature irradiation.

Effect of high-temperature electron irradiation in thin gate oxide FD-SOI n-MOSFETs

The degradation of deep submicrometer (0.1 /spl mu/m) fully depleted silicon-on-insulator n-MOSFETs subjected to 2-MeV electron irradiation at different temperatures is reported. The radiation-induced damage is investigated by studying the static characteristics of devices with different geometries and bias conditions. The change of the front and back-channel parameters, the impact of the gate coupling effect and the gate-induced floating body effects and the irradiation temperature dependence of these degradations are clarified. It is found that the degradation of the electrical properties tends to be small for high temperature irradiation compared with that for room temperature.

Effects of high temperature electron irradiation on trench-IGBT

The degradation of the electrical properties of IGBTs (Insulated-Gate Bipolar Transistors) by 2-MeV electron irradiation at high-temperatures was studied. The irradiation temperatures were 25, 100, 200 and 300∘C, and the fluence was fixed at 1015 e/cm2. For most experimental conditions, the threshold voltage (VTH) is observed to recover partially during 100∘C and the saturation voltage (VCEsat) increase is most pronounced at 100∘C. It is shown that in this irradiation temperature range, the temperature dependency of the voltage shift due to the radiation-induced interface traps (Δ Vit) and the voltage shift due to the radiation-induced oxide traps (Δ Vot) are different, which suggests a possible degradation mechanism for these phenomena. It is tentatively suggested that the diffusion of hydrogen released from the gate by the 2-MeV electrons passivates the interface traps during the high temperature irradiation.

Radiation damages of InGaAs photodiodes by high-temperature electron irradiation

Results are presented of a detailed study of the effects of high-temperature 2-MeV electron irradiation on the performance degradation of InGaAs photodiodes. The macroscopic device performance will be correlated with the radiation-induced defects, observed by DLTS. It was found that the dark current increases after irradiation, while the photo current decreases. After irradiation, one majority electron capture level with ( E c−0.37 eV) was induced in the n-InGaAs layer, while no minority hole traps were found. Additionally, the degradation of the device performance and the introduction rate of the lattice defects decrease with increasing irradiation temperature. For a 300 °C irradiation, the reduction of the photo current is only 40% of the starting value. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperatures.

Induced lattice defects in InGaAs photodiodes by high-temperature electron irradiation

Results of a detailed study of the effects of high-temperature 2-MeV electron irradiation on the performance degradation of InGaAs photodiodes are presented. The macroscopic device performance will be correlated with the radiation-induced defects observed by deep level transient spectroscopy. It was found that the dark current increases after irradiation, while the photocurrent decreases. After irradiation, one majority electron capture level with (Ec−0.37eV) was induced in the n-InGaAs layer, while no minority hole traps were found. Additionally, the degradation of the device performance and the introduction rate of the lattice defects decrease with increasing irradiation temperature. For a 300°C irradiation, the reduction of the photocurrent is only 40% of the starting value. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperatures.

Effect of irradiation temperature on radiation damage in electron-irradiated MOS FETs

Results are presented of a study of radiation damage by high-temperature electron irradiation in submicron MOS FETs with standard thermal oxide and nitrogen annealed gate oxide as gate dielectric material. n-Channel MOS FETs were irradiated by 2-MeV electrons for the fluence of 1×10 15 e/cm 2 at 30, 100 and 200 °C. The drain leakage current in the cut-off region of MOS FETs increased with irradiation and the increase at 30 °C irradiation was the largest. However, the degradation of maximum transconductance of the MOS FETs tended to increase with increasing irradiation temperature due to the scattering induced by the change in positive trapped charge density and interface state density.

Photoluminescence characterization of defects created in electron-irradiated silicon at elevated temperatures

Photoluminescence (PL) spectroscopy is employed to investigate radiative defects created in Si during electron-irradiation at elevated temperatures. The use of high temperature during electron irradiation has been found to affect considerably the defect formation process. The effect critically depends on the temperature of the irradiation as well as doping of the samples. For carbon-lean Si wafers high temperature electron irradiation stimulates the formation of extended defects, such as dislocations and precipitates. For carbon-rich Si wafers the increase of irradiation temperature up to 300°C enhances the formation of the known carbon-related defects. In addition, several new excitonic PL lines were observed after electron irradiation at T≥450°C. The dominant new PL center gives rise to a BE PL emission at 0.961 eV. The electronic structure of the 0.961 eV defect is discussed based on temperature-dependent and magneto-optical studies.

Effect of high-temperature electron irradiation on the formation of radiative defects in silicon

Defect formation processes in silicon caused by electron irradiation performed at elevated temperatures are studied in detail using photoluminescence (PL) spectroscopy. The use of high temperature during electron irradiation has been found to affect considerably the defect formation process. In particular, several new unknown excitonic PL lines were discovered in carbon-rich Si wafers subjected to electron irradiation at temperatures higher than 450°C. The dominant new luminescent center gives rise to a bound exciton PL emission at 0.961eV. The center is shown to be efficiently created by electron irradiation at temperatures from 450°C up to 600°C. The electronic structure of the 0.961eV PL center can be described as a pseudodonor case, where the hole is strongly bound at a level 187meV above the valence band, while the electron is a effective-mass-like particle weakly bound by ≈21meV in the BE state.

The migration of metal atoms through carbon onions

Metallic nanocrystals such as cobalt or gold are encapsulated by spherical graphitic shells under high-temperature electron irradiation. The irradiation promotes a heavy contraction of the carbon onions. The contraction forces the metal atoms to migrate outwards through the shells, even without further irradiation. This leads to a gradual but complete displacement of the encapsulated crystals. In-situ observation in an electron microscope allows shrinkage of the encapsulated crystals and migration of the atoms through the shells to be monitored. The experiment shows that spherically curved graphene layers are permeable to metal atoms.

High-temperature electron irradiation and radiation-thermal technology for utilization, purification and production of some metals

High-temperature irradiation by the beam of 1.2–1.6 MeV accelerated electrons has been used for production Pt, Pd, Mo, Co, Cu and Ni from desactivated Pt(Pd)-containing reforming catalysts, molybdenum sulfide hydrodesulphurization catalysts and hydrogenation catalyst waste material. The radiation-induced decomposition of supported Ni(Co)-Mo/Al 2O 3 sulfide catalyst and organic fragments of hydrogenation catalyst wastes has been studied. Radiolysis product distributions are shown as function of time (time up to 1, 0 h) and temperature (570–1400K). There was made a principle scheme of the first technological unit for radiation-thermal utilization, purification and production of some metals from solid wastes material.

Electrical and optical properties of defects in silicon introduced by high-temperature electron irradiation.

2-MeV electron irradiation of Si at elevated temperature creates a dominant deep level at the energy E/sub c/-0.36 eV in addition to the oxygen vacancies. This level, which is less significant in room-temperature-irradiated Si, is found to be an efficient recombination center in the present situation. The optical cross section of this level measured by deep-level optical spectroscopy reveals a fine structure superimposed on the main transition. This fine structure is considered to be related to a new resonant phonon mode coupled with the above defect. The isochronal annealing behavior shows that this defect might be a kind of vacancy-oxygen complex. With the assumption of a V/sub 2/-O/sub 2/ complex structure, a calculation based on the Green's-function method of lattice dynamics indicates the existence of a defect-induced resonant phonon mode with energy of 10 meV, which is in good agreement with the experimental observation.

STUDY OF THE DEFECTS IN SILICON PRODUCED BY HIGH TEMPERATURE ELECTRON IRRADIATION

A study of defects in silicon produced by hightemperature electron irradiation was carried out. It was found that the introduction rate of defect increased with the temperature at which the samples were irradiated by electron. After the temperature reached an "extreme" value Tm, the introduction rate of defect began to decrease. The Tm value was related to the annealing activation energy of defect. It was also found that the density of E3 (Ec-0.36 eV) defects greatly increased in hightemperature electron irradiation. When electron irradiation was carried out at 330℃, the density of E3 defects was about 6 times as large as that at room temperature. The possible structure of the E3 defect is multivacancy-oxygen complex.

Defects introduced by high temperature electron irradiation in n-GaAs

Bulk Czochralski and VPE layers of n-GaAs have been irradiated with 1 MeV electrons at about 300°C, temperature at which primary defects are not stable. Up to seven electron traps are thus observed to be introduced. The dominant trap (I1) has an activation energy and a capture cross section very close to the so-called EL2 center, which suggests that EL2 could be introduced by a high temperature electron irradiation. The introduction rate of I1 is about 1cm-1, that is the same order of magnitude as those of the traps (E-traps) introduced by a room temperature irradiation, and two orders of magnitude larger than those of the traps observed after the annealing (200–300°C) of the E-traps. With a starting dopant concentration of 2×1016cm-3, we have obtained a quite complete compensation of free carriers after a total fluence of 1017e/cm2.

MOS and Thyristor Damage Parameters after 2.5 and 15 MeV High Temperature Electron Irradiation

MOS capacitors and thyristors are irradiated with 2.5 and 15 MeV electrons. Minority carrier lifetime τsc, surface recombination velocity s, flatband voltage UFB, breakdown voltage UBR, and breakdown time TBR for the MOS capacitors, circuit commutated turn-off time τq, and on-state voltage UT for the thyristors are measured as a function of dose. The irradiation temperature is 300 or 22°C. In the latter case, this is followed by a 300°C postirradiation anneal. The results for the thyristors are compared to those of gold diffused ones. Self-annealing is observed. Damage constants are kτLI = 2.4 × 10−8 cm2/s (Tirr = 300°C, 15 MeV) and 3.6 × 10−9 cm2/s (300°C, 2.5 MeV). No degradation is observed for the MOS capacitors irradiated at 300°C. 22 °C irradiation leads to a damage constant kτsc = 2 × 10−10 cm2/s (15 MeV) and kτsc = (2 to 5) × 10−10 cm2/s (2.5 MeV). Subsequent annealing at 300°C yields kτsc = 2.3 × 10−11 cm2/s (15 MeV) and kτsc = 9 × 10−11 cm2/s (2.5 MeV). MOS-Kondensatoren und Thyristoren werden mit 2,5 und 15 MeV Elektronen bestrahlt. Die Minoritagerlebensdauer τsc, die Oberflachengenerationsgeschwindigkeit s, die Flachbandspannung UFB, die Durchbruchsspannung UBR und die Durchbruchshaltezeit TBR werden in Abhangigkeit von der Dosis fur die MOS-Kondensatoren bestimmt; fur die Thyristoren werden Freiwerdezeit τq und Vorwartsspannung UT gemessen. Die Bestrahlungstemperaturen sind 300 oder 22 °C. Im zweiten Fall folgt der Bestrahlung ein 300°C Temperschritt. Die Ergebnisse an den Thyristoren werden mit denen golddiffundierter verglichen. Selbstheilung wird beobachtet, Schadigungstanten sind kτLI = 2,4 × 10−8 cm2/s (Tirr = 300°C, 15 MeV) und 3,6 × 10−9 cm2/s (300°C, 2.5 MeV). Bei den MOS-Kondensatoren, die bei 300°C bestrahlt werden, ist keine Schadigung sichtbar. 22 °C-Bestrahlung fuhrt zu einer Schadigungskonstante kτsc = 2 × 10−10 cm2/s (15 MeV) und kτsc = (2 bis 5) × 10−10 cm2/s (2,5 MeV). Anschliesende Temperung bei 300°C ergibt kτsc = 2,3 × 10−11 cm2/s (15 MeV) und kτsc = 9 × 10−11 cm2/s (2,5 MeV).

Nature of Secondary Defects in Silicon Produced by High Temperature Electron Irradiation

Nature of Secondary Defects in Silicon Produced by High Temperature Electron Irradiation

Effect of high temperature electron irradiation in gold

Abstract Pure gold is electron irradiated with 2.8 MeV electrons at 450±50°C. Both electrical resistivity and transmission electron microscopy showed damage which anneals at about 800°C.