HRTEM OBSERVATION OF ELECTRON-IRRADIATION-INDUCED DEFECTS PENETRATING THROUGH A THIN FOIL OF GERMANIUM

The structure of defects introduced in germanium under 2 MeV electron irradiation was studied by means of electron diffraction and high-resolution electron microscopy. It has been observed that the {111} stacking fault of vacancy type interacts with the rodlike defect with hexagonal structure. The (113) defect of interstitial type exhibits similar electron diffraction patterns and high-resolution electron image to those in Si. An analysis of HRTEM images shows that the defect structure on (113) in Ge is isomorphous to that in Si. The density of interstitial atoms in the (113) defect is estimated at 0.65 x 8/square-root 11 a2, where a is a lattice parameter of Ge. Self-interstitial atoms are located at lattice points on the extra two sheets of the (113) net plane and constitute interstitial-atom chains in the [110BAR] direction. It is revealed that nearly 35% of the lattice points are systematically unoccupied to form "vacancy" chains in the same direction. Thus, the interstitial and "vacancy" chains are arranged in short-range correlation.