Anisotropy in the positron 2D angular correlation of annihilation radiation for singly negative divacancies in Si

Interesting features of positron two-dimensional angular correlation of annihilation radiation (2D-ACAR) distribution for singly negative divacancies in Si are studied experimentally and theoretically. Anisotropy of the distribution is successfully detected for a specimen with aligned divacancies and is well reproduced by first-principles calculations based on the two-component density-functional theory. The present calculation demonstrates that the anisotropy reflects the characteristic distribution of electrons around the divacancies, indicating that the 2D-ACAR is an effective tool to provide microscopic information on vacancy-type defects.