Ion-beam induced damage and annealing behaviour in SiC

2013

Phys. Status Solidi C

The influence of irradiation induced damage on the transport of implanted species in poly and single crystalline silicon carbide is investigated. For this purpose published diffusion results of strontium, silver, iodine and cesium are compared with the associated evolution of defect profiles determined by α-particle channelling in a backscattering geometry. Strong diffusion takes place in the amorphized surface layer of room temperature implanted 6H-SiC during annealing at 1100 °C, which drops below the detection limit of 10 -21 m 2 s -1 as soon as re-crystallization is completed. Diffusion in samples implanted above the critical amorphization temperature is only observed when simultaneously a significant reduction of defect density occurs. No diffusion into the undamaged bulk is detected at temperatures up to 1500 °C. The observed diffusion behaviour is explained by a defect related trapping and release mechanism. Normal grain boundary diffusion of silver and iodine occurs in CVD-SiC.

Section: Strontium Implantssupporting

confidence: 84%

Influence of radiation damage on diffusion of fission products in silicon carbide

Friedland

Hlatshwayo

2013

Phys. Status Solidi C

“…However, it is generally accepted that implanting SiC at 350°C and at 600°C results in the SiC remaining crystalline albeit with many point defects present [7,8]. Figure 1 shows an in-lens SEM image of 6H-SiC bombarded by 360 keV Ag + ions at room temperature.…”

Section: Resultsmentioning

confidence: 99%

SEM analysis of ion implanted SiC

Malherbe

Nuclear Instruments and Methods in Physics Research Section B:

Botha

et al. 2013

Self Cite

SiC is a material used in two future energy production technologies, firstly as a photovoltaic layer to harness the UV spectrum in high efficient power solar cells, and secondly as a diffusion barrier material for radioactive fission products in the fuel elements of the next generation of nuclear power plants. For both applications, there is an interest in the implantation of reactive and nonreactive ions into SiC and their effects on the properties of the SiC. In this study 360 keV Ag + , I + and Xe + ions were separately implanted into 6H-SiC and in polycrystalline SiC at various substrate temperatures. The implanted samples were also annealed in vacuum at temperatures ranging from 900°C to 1600°C for various times. In recent years, there had been significant advances in scanning electron microscopy (SEM) with the introduction of an in-lens detector combined with field emission electron guns. This allows defects in solids, such as radiation damage created by the implanted ions, to be detected with SEM. Cross-sectional SEM images of 6H-SiC wafers implanted with 360 keV Ag + ions at room temperature and at 600°C and then vacuum annealed at different temperatures revealed the implanted layers and their thicknesses. A similar result is shown of 360 keV I + ions implanted at 600°C into 6H-SiC and annealed at 1600°C. The 6H-SiC is not amorphized but remained crystalline when implanting at 600°C. There are differences in the microstructure of 6H-SiC implanted with silver at the two temperatures as well as with reactive iodine ions. Voids (bubbles) are created in the implanted layers into which the precipitation of silver and iodine can occur after annealing of the samples. The crystallinity of the substrate via implantation temperature caused differences in the distribution and size of the voids. Implantation of xenon ions in polycrystalline SiC at 350°C does not amorphize the substrate as is the case with room temperature heavy ion bombardment. Subsequent annealing of the implanted polycrystalline samples leads to increased thermal etching effects such as grain boundary grooving. Damage due to channelling (or non-channelling) in the different crystallites resulted also in differences in thermal etching in the crystallites.

“…1 depicts -particle RBS-channeling spectra of strontium implantations in single crystalline samples at different temperatures, showing the well-known radiation hardness of SiC above 300 ºC [8,9]. It leaves the crystal structure intact if implanted above that temperature, although high densities of extended defects are present, which leads to the strong damage peaks in the aligned spectra.…”

Section: Resultsmentioning

confidence: 99%

Influence of radiation damage on strontium and iodine diffusion in silicon carbide

Friedland

Journal of Nuclear Materials

Malherbe

et al. 2012

Self Cite

Abstract.The transport behaviour of strontium and iodine through single and poly crystalline SiC wafers was investigated using ion beam analysis and electron microscopy. Fluences of 2×10 16 Sr + cm -2 and 1×10 16 I + cm -2 were implanted at temperatures between 23 °C and 600 °C with an energy of 360 keV, producing an atomic density of approximately 1.5% at the projected ranges of about 120 nm and 90 nm respectively. The broadening of the implantation profiles and its dependence on implantation parameters was determined by isochronal and isothermal annealing studies at temperatures up to 1400 °C. The strong influence of radiation damage on diffusion after room temperature implantations was observed in all cases during the initial annealing stages at 1000 °C. This is a result of the highly disordered crystal lattice, which re-crystallizes at this temperature. In hot implantations this effect is largely reduced but an additional transient diffusion process was observed at 1400 °C for strontium, which is related to defect annealing. Impurity trapping by extended defects is obviously an important effect.