Large angle convergent beam electron diffraction strain measurements in high dose helium implanted silicon

Large angle convergent beam electron diffraction (LACBED) technique has bee n applied to < 110 > TEM cross section of silicon samples implanted with 2 x 10(16) cm(-2) He ions at an energy of 20 KeV in order to evaluate the str ess/strain field in the implanted layer. The stress/strain field depends on the mismatch between the lattice of the silicon substrate and the one of t he defective layer which contains clusters of point defects and small He bu bbles. Lattice mismatch causes changes in the spacing and inclination of di ffraction planes producing a shift and a rotation of diffraction intensity lines (Bragg contours (BC)) visible in LACBED patterns. In particular, when the electron beam is parallel to the rotation axis, the BC simply rotate. This is the case of mismatches observed with (333) BC when the electron bea m is incident on the sample along a direction close to < 110 > zone axis. M easurements show a peak of the stress/strain field (intensity 1.5 GPa) at a depth close to the helium projected range, where small bubbles occasionall y form aggregate oriented along < 011 > direction. (C) 2000 Elsevier Scienc e S.A. All rights reserved.