Observations of point defects in silicon by means of dark-field lattice plane imaging

The possibilities are investigated of the dark-field lattice imaging method for observing single point defects. The contrast of single point defects is shown to be sufficiently high to be observed. The value of contrast is mainly determined by the electrical characteristics of single point defects. The intensity distribution in the dark-field lattice image is strongly connected with the crystal structure projection for a crystal thickness below 10 nm. Positions of intensity maxima coincide with those of double Si atom columns in the (110) projection. Two types of contrast features may be observed by using this technique both, in gold doped Si crystals and in Si irradiated by high-energy electrons. Abnormally bright and dark contrast in the image may be attributed to Au+ or Si+ split interstitials and vacancies V–, respectively. The presence of vacancies in Au-doped Si shows that gold diffusion in silicon is controlled by the Frank-Turnbull mechanism.