Vacancy-type defects in Ar and B gas cluster ion-implanted Si were probed by mono-energetic positron beams. The acceleration energy of the clusters ranged between 20 and 60keV, and the mean cluster size was 2 x 103atoms. Doppler broadening spectra of the annihilation radiation were measured, and the vacancy-rich region was found to localize at a depth of 0 to 13nm. Measurements of the lifetime spectra of positrons revealed that two different defect species coexisted in the damaged region introduced by Ar gas cluster implantation, and these were identified as divacancy-type defects and large vacancy clusters filled with Ar. The formation of the vacancy clusters was attributed to extremely high temperature and its rapid transients in impact regions of Ar cluster ions. For B gas cluster ion implanted Si, the detected momentum distribution of electrons in the damaged region was broader than that in the defect free Si, suggesting that the trapping of positrons by open spaces adjacent of B clusters.

Vacancy-Type Defects Introduced by Gas Cluster Ion-Implantation on Si Studied by Monoenergetic Positron Beams. A.Uedono, T.Moriya, T.Tsutsui, S.Kimura, N.Oshima, R.Suzuki, S.Ishibashi, H.Matsui, M.Narushima, Y.Ishikawa, M.Graf, K.Yamashita: Japanese Journal of Applied Physics, 2012, 51[11], 111801