TRANSMISSION ELECTRON-MICROSCOPY AND HIGH-RESOLUTION ELECTRON-MICROSCOPY STUDIES OF STRUCTURAL DEFECTS INDUCED IN 6H ALPHA-SIC SINGLE-CRYSTALS IRRADIATED BY SWIFT XE IONS

Single crystals of 6H alpha-SiC, p type, were irradiated with 5.5 GeV Xe ions supplied by GANIL close to the [0001] crystal axis with fluences up to 10(15) Xe cm-2. After irradiation the colour of the crystals changed in their radiated zone. Transmission electron microscopy observations of samples which had been irradiated and then annealed at 1373 K revealed the presence of loops lying in basal and prismatic planes. Basal faults have an interstitial character with a Burgers vector of the type 1/6[0001]. Contrast analyses as well as high-resolution electron microscopy observations allowed us to propose a geometrical model for the new defects observed in prismatic planes of the 6H polytype. These prismatic loops are the consequence of interstitial precipitation in {1012BAR} pyramidal planes; the fault plane has a 'zigzag' configuration and a Burgers vector of the type 1/18[8081BAR].