Understanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the nonequilibrium processes of radiation damage in... (Read more)

Undoped n-GaN grown by two different metallorganic chemical vapor deposition (MOCVD) techniques, standard MOCVD and epitaxial lateral overgrowth, and Mg-doped p-GaN prepared by hydride vapor phase epitaxy and molecular beam epitaxy were irradiated with fast reactor neutrons to the high... (Read more)

Low-temperature photoluminescence spectroscopy has revealed a series of features labeled S₁, S₂, S₃ in n-type 6H-SiC after neutron and electron irradiation. Thermal annealing studies showed that the defects S₁,... (Read more)

Electron spin resonance (ESR) was used to study neutron-induced defects in silicon as functions of anneal temperature T_an. For T_an below 200 °C, the ESR response is dominated by the Si-P3 and Si-P6 spectra, as observed before. At T_an=200 ... (Read more)

Electron-paramagnetic-resonance (EPR) and electron-spin-echo (ESE) studies have been performed that show that isolated V_Si^-, V_Si⁰, and V_C vacancies are the dominant intrinsic paramagnetic defects in SiC treated by room-temperature neutron... (Read more)

We investigated radiation-induced defects in neutron-irradiated and subsequently annealed 6H-silicon carbide (SiC) with electron paramagnetic resonance (EPR), the magnetic circular dichroism of the absorption (MCDA), and MCDA-detected EPR (MCDA-EPR). In samples annealed beyond the annealing... (Read more)

We use electron paramagnetic resonance and electron nuclear double resonance to identify the negatively charged Si vacancy in neutron-irradiated 4H SiC. The identification is based on resolved ligand hyperfine interactions with carbon and silicon nearest and next nearest neighbors and on the... (Read more)

Three varieties of E′ centers with a spin state, S = 1/2, and with a G-tensor, Gx Gy 2.0003, Gz 2.0018, were identified in the early reports on paramagnetic states in irradiated α-quartz. The atomic structure of two of these had an hydrogen ion (proton) in nearby sites and hence... (Read more)

A review is given on the diffusion, solubility and electrical activity of 3d transition metals in silicon. Transition elements (especially, Cr, Mn, Fe, Co, Ni, and Cu) diffuse interstitially and stay in the interstitial site in thermal equilibrium at the diffusion temperature. The parameters of the liquidus curves are identical for the Si:Ti — Si:Ni melts, indicating comparable silicon-metal interaction for all these elements. Only Cr, Mn, and Fe could be identified in undisturbed interstitial sites after quenching, the others precipitated or formed complexes. The 3d elements can be divided into two groups according to the respective enthalpy of formation of the solid solution. The distinction can arise from different charge states of these impurities at the diffusion temperature. For the interstitial 3d atoms remaining after quenching, reliable energy levels are established from the literature and compared with recent calculations. (Read more)

Optical detection of magnetic resonance is reported for the 0.97-eV luminescence in neutron-irradiated silicon. The resonance is of an excited triplet (S=1) state of the defect, which is not the radiative state, known to be a singlet (S=0). The spectrum is unusual in that it is characteristic of a... (Read more)

This paper deals with an electron-paramagnetic-resonance study of the Si-B3 center, which was first reported by Daly. The Si-B3 center is a secondary defect which forms upon annealing between 50 and 175?C in irradiated boron-doped silicon and is stable up to ?500?C. Our studies indicate that the... (Read more)

The Si-P6 spectrum shows an intrinsic tetragonal symmetry with the C₂ axis along ?100? and distortion forces the principal axes of the g tensor to be displaced in the {100} plane. The g tensor previously identified by Jung and Newell was found to be due to the motionally averaged state... (Read more)

Using electron paramagnetic resonance (EPR) the indensity of the point defects produced by fast neutron irradiation of silicon at room temperature has been determined and the concentration of each defect has been measured. Irradiations were perfrmed at an unmoderated fast burst reactor to assure that damage from gamma irradiation could be neglected and that all the obsserved damage could be attributed to desplacements by fast neutrons. Total fast neutron fluence between 1.2×10¹⁵ n/cm² and 7×10¹⁵ n/cm² was used. The initial rate of removal of the phosphorus donor agrees with the initial carrier removal. However, the production rate for the paramagnetic damage centers is approximately 10 per cent of the carrier removal and less than 1 per cent of the estimated number of displacements per neutron collision. For samples containing approcimately 10¹⁶ phosphorus donoers/cm³, the neutral spectrum is observed simultaneously with the negative divacancy spectrum (Si-G7) in both crucible-grown and float-zone crystals. According to the energy level scheme determined for these spectra in electron irradiation silicon, these spectra cannot appear simultaneously if the sample is in equilibrium and uniformly irradiated. From the observation of these spectra, it is concluded that the damage concentrarion and hence the depth of the Fermi level is nonuniform on a microscopic scale. These results are interpreted according to the cluster model for the neutron damage. The cluster consists of a core of damaged silicon with the Fermi level at the center of the band gap and a surrounding space charge region. Outside the space charge region, the Fermi level is the same as in undamaged silicon. It is concluded that the low production rate of the point defects and the non-uniform Fermi level constitute microscopic evidence for the defect cluster model of fast neutron damage in silicon.

Lines in the EPR spectrum of ZnO crystals irradiated by 3.6 × 1018cm−2 fast neutrons are ascribed to holes on oxygen atoms in the basal plane of O4 tetrahedra which surround Zn vacancies. (Read more)

Electron spin resonance produced in silicon by fast neutron irradiation was studied. The temperature of the samples during the irradiation was about 50?C. Different spectra were observed depending on the Fermi level in the irradiated sample. Samples with the Fermi level near the middle of the energy... (Read more)