Analysis of dislocation loops by means of large-angle convergent beam electrondiffraction

Abstract

Diffusion-induced dislocation loops in GaP and GaAs were analysed by means oflarge-angle convergent beam electron diffraction (LACBED) and conventionalcontrast methods of transmission electron microscopy. It is demonstrated thatLACBED is perfectly suited for use in analysing dislocation loops. The methodcombines analyses of the dislocation-induced splitting of Bragg lines in aLACBED pattern for the determination of the Burgers vector with analyses of theloop contrast behaviour in transmission electron microscopy bright-field imagesduring tilt experiments, from which the habit plane of the dislocation loop isdetermined. Perfect dislocation loops formed by condensation of interstitial atomsor vacancies were found, depending on the diffusion conditions. The loops possess{110}-habit planes and Burgers vectors parallel to ⟨110⟩. TheLACBED method findings are compared with results of contrast analyses basedon the so-called ‘inside–outside’ contrast of dislocation loops. Advantages of theLACBED method consist in the possibility of determining the complete Burgersvector of the dislocation loops and of an unambiguous and fast loop type analysis.