[en] Damage profiles in SiC after implantation of 150 keV carbon ions at 77 K with fluences ranging between 4 x 10¹⁴ and 3.2 x 10¹⁵ cm^-2 were determined by ion channeling in a backscattering geometry. Critical damage energies leading to amorphization were compared for different penetration depths. The results indicate a strong dependence on inelastic stopping processes. A comparison of amorphization energies obtained for heavier ions confirm such dependence

[en] At ion energies with inelastic stopping powers less than a few keV/nm, radiation damage is thought to be due to atomic displacements by elastic collisions only. However, it is well known that inelastic processes and non-linear effects due to defect interaction within collision cascades can significantly increase or decrease damage efficiencies. The importance of these processes changes significantly along the ion trajectory and becomes negligible at some distance beyond the projected range, where damage is mainly caused by slowly moving secondary recoils. Hence, in this region amorphization energies should become independent of the ion type and only reflect the properties of the target lattice. To investigate this, damage profiles were obtained from α-particle channeling spectra of 6H-SiC wafers implanted at room temperature with ions in the mass range 84 ⩽ M ⩽ 133, employing the computer code DICADA. An average amorphization dose of (0.7 ± 0.2) dpa and critical damage energy of (17 ± 6) eV/atom are obtained from TRIM simulations at the experimentally observed boundary positions of the amorphous zones.

[en] Damage profiles in diamond after irradiation with 75 keV carbon ions at implantation temperatures ranging between 77 and 600 K were determined by ion channeling analysis in a backscattering geometry. Critical damage energies for irreversible transition to the graphitic phase were extracted by annealing studies. The results, which show a strong increase above room temperature for the shallower of the two transition points, and a smaller increase for the deeper transition point, indicate a significant dependence of these energies on the accompanying electronic energy loss

[en] The influence of the finite depth resolution due to instrumental resolution and energy straggling on depth profiling, using backscattering or nuclear reaction techniques, is studied. It is found that in cases of large concentration gradients such as those found in ion implantation profiles, absolute peak values are in error by as much as 20% if no corrections are applied. (Auth.)

[en] Single crystals of magnesium oxide were implanted with 150 keV krypton ions at room temperature. Fluences ranged between 5 x 10¹⁴ and 5 x 10¹⁵ ions cm^-2 using a dose rate of approximately 10¹³ ions cm^-2s^-1. Samples were isochronally annealed in vacuum at temperatures of 400, 600, 800 and 1000 C. Damage depth profiles were determined before and after each annealing cycle by α-particle channeling using a backscattering geometry. Relative defect densities were obtained from aligned spectra by numerical integration of the dechanneling rate equation. The experimental results confirm a mixed damage structure, which probably consists of randomly disordered regions and extended defects. Complete annealing of these two components occurs at temperatures above 600 and 800 C respectively. (orig.)

No abstract available

No abstract available

[en] Diffusion of heavy noble gas atoms in irradiation damaged single crystalline silicon carbide and the thermal etching of it is investigated at temperatures of 1300 °C and 1400 °C. For this purpose 360 keV krypton and xenon ions were implanted in commercial 6H-SiC wafers at 600 °C, which is far above the critical amorphization temperature of the target material. Width broadening of the implantation profiles and the retention of krypton and xenon during isothermal annealing was determined by RBS-analysis, whilst damage profiles were simultaneously obtained by α-particle channelling. No diffusion and no loss of the implanted species is detected in the implanted samples after isothermal annealing for 40 h at 1400 °C. However, thermal etching of the target material is observed at both annealing temperatures and leads at 1400 °C to a significant shift of the implantation profile towards the surface due to sublimation. RBS analysis shows that this occurs mainly during the initial stage of isothermal annealing, while surface loss during prolonged annealing is minimal. The resulting topographical modification of the surface during annealing was studied by scanning electron and atomic force microscopy. It indicates that the observed phenomenon is due to a relatively strong dependence of thermal etching on the defect density in the surface region, while the evolving surface roughness seems not to play a decisive role.

[en] Data for the ¹⁴⁴Sm(¹³C,¹²C)¹⁴⁵Sm and ¹⁴⁴Sm(¹³C,¹⁴C)¹⁴³Sm reactions were taken at incident energies of 66 and 72 MeV respectively. In addition, elastic scattering of ¹³C from ¹⁴⁴Sm at 66 MeV was performed to obtain optical model parameters for cross section calculations. Experimental cross sections along with DWBA predictions for ¹⁴⁴Sm(¹³C,¹⁴C) and spectroscopic factors for ¹⁴³Sm are given. Results for the ¹⁴⁴Sm(¹³C,¹²C) reaction are not as clear. (2 figures, 1 table) (U.S.)

[en] Diffusion behaviour of aluminium in silicon at temperatures up to T=900 deg. C was investigated by nuclear reaction analysis (NRA). Previously published results predict diffusion coefficients ranging from 3x10^-15 to 1.3x10^-13 cm² s^-1 at T=900 deg. C. In a first series aluminium films were vapour deposited onto Si<1 0 0> substrates, followed by isochronal annealing. The diffusion coefficient was found to be less than 10^-15 cm² s^-1 at 900 deg. C. In a second series Si<1 0 0> and Si<1 1 1> samples were implanted at room temperature and at 250 deg. C with a fluence of 5x10¹⁶ Al⁺ cm^-2. For the samples implanted at 250 deg. C and subsequently annealed at 900 deg. C, the diffusion coefficient was again found to be less than 10^-15 cm² s^-1, while diffusion coefficients of the order of 10^-13 cm² s^-1 were observed for the room-temperature implanted samples. Channeling analyses revealed extensive radiation damage in the latter samples, which was still present after annealing for 1 h at 900 deg. C. In contrast to this, the samples implanted at 250 deg. C were virtually defect-free. From this it is concluded that the high values observed for the room-temperature implants are due to defect-assisted diffusion