Applications of slow positron beams to study point defect distributions near solid surfaces

Injection of monoenergetic “slow” (0 to 30 keV) positrons into solid materials can be used to obtain unique information on depth distribution of open-volume lattice defects near solid surfaces. This is due to the tendency of thermalized positrons to become localized into regions of low atomic density. These include vacancies, their agglomerates and dislocations in metals, and negatively-charged vacancies and impurities in semiconductors. Specific information on the type and density of defects can be obtained starting from the outermost atomic layer down to a few μm depths. Applications to studies of damage associated with ion-implanted semiconductors, sputtered surfaces and growth processes of thin epitaxial heterostructures are presented.