TEM INVESTIGATION OF GRAIN BOUNDARIES IN POLYCRYSTALLINE SILICON

Une étude par microscopie électronique en transmission de la structure de joints de grains dans du silicium polycristallin est présentée, pour deux types de joints voisins des désorientations de coïncidence Σ = 7 et Σ = 9. Dans le joint Σ = 7, un réseau de dislocations secondaires existe ainsi qu'une série de marches. Dans le joint Σ = 9, nous avons trouvé un système de franges α (causé par une translation des deux grains le long du plan du joint) et un réseau de dislocations secondaires dont la structure dépend des conditions de diffraction.The structure of two near-coincidence boundaries (close to a Σ = 7 and a Σ = 9 misorientation) occurring in commercial poly-silicon has been examined in TEM. Both the structure of secondary dislocation networks as well as the occurrence of α-fringes (indicating a relative translation of the crystals along the boundary) were investigated. The near Σ = 7 boundary is found to contain a simple network in addition to a regular array of steps. The near Σ = 9 boundary exhibits α-fringes and a dislocation network which appears as a different structure for different diffraction conditions