The determination of the geometry and nature of small Frank loops using the weak‐beam method

SUMMARY Theoretical and experimental investigations have been carried out to determine under which conditions weak‐beam images can give useful information on the geometry, size and nature of small Frank loops. Suitable experimental conditions for obtaining such information were deduced from computed weak‐beam images of Frank loops under various selected loop and foil orientations and diffraction vectors. Experiments to check these deductions were performed in silicon damaged by irradiation with phosphorus ions. It was found that the geometry and size of loops of diameter 8 nm (80 Å) viewed normal to their habit plane was well defined by weak‐beam images taken in {220} reflections lying in the loop plane for which g.b = 0 and g.b × u ≠ 0. By imaging in reflections with g vectors not in the loop plane the enclosed stacking faults were imaged (thus confirming the loops to be Frank loops) and the sense of the Burgers vector (i.e. the loop nature) was determined.