Assessment of the normalization procedure used for interlaboratory comparisons of positron beam measurements

Variable-energy positron annihilation data from ion implanted and unirradiated Si and SiO2 were obtained at five separate laboratories. Line-shape analysis of the 511 keV annihilation gamma rays yielded normalized S parameter signatures for radiation defect distributions in both types of samples. Laboratory-to-laboratory variations are found which, although small, lie outside the expected range of reproducibility. Large variations found in the extracted values for positron diffusion lengths L+ in silicon are identified and thought to arise from differences in sample surface conditions. Possible sources of the observed discrepancies are discussed, together with methods for reducing them. (C) 1999 American Institute of Physics. [S0021-8979(99)01413-9].