Characterization of superlattices using positron annihilation

Superlattices (SLs) of Si and SiO2 with layer dimensions of 10–40 Å grown by different techniques have been characterized using a slow positron beam. The growth methods include techniques both with and without hydrogen. The annihilation characteristics of the individual materials present in the SL are first determined using S and W plots, which indicate the significant impact which hydrogen in the growth environment has on the defects present. Core annihilation spectra gathered using a two-detector coincidence arrangement are then measured for the separate annihilation sites. When interface defects are passivated by growth in a H-containing atmosphere, the annihilation spectra of the SL may be reconstructed by superimposing the spectra of bulk amorphous Si and SiO2 weighted by the annihilation fractions. This indicates the usefulness of applying the coincident arrangement to interpretation of data gathered on SL samples.