1D-ACAR Studies of As-Grown Impurity Centers in Silicon

摘要

The results of measurements of the one-dimensional angular correlation of the annihilation radiation (1D-ACAR) in Fz-Si and Cz-Si having different carbon content are presented. The analysis of data has been carried out on the basis of the independent particle model for outer shell core and valence electrons. The characteristic electron-positron ionic length and the "cut-off" angle of 1D-ACAR (to be characterised both by the ionic radii of atoms and the electron density in the lattice site where the annihilation of positron occurs) have been determined by the experimental findings for the investigated silicon as well as for some related materials (diamond, SiC, SiO_2, and others). The systematic 1D-ACAR data obtained for the A~3B~5 compounds have been used as a basis for the qualitative description of the 1D-ACAR results obtained for various materials of Fz-Si, Cz-Si, SiC, C(diamond), SiO_2 (quartz). It has been shown that the partial positron localisation associated with the carbon as-grown impurity centers in silicon is intimately related to the both high-momentum component of 1D-ACAR and average positron annihilation rate. A certain correlation (and as it has been expected the rather complex one) between the carbon/oxygen content and the positron annihilation characteristics has been revealed.