Depth-resolved positron beam studies were made of Ar-bombarded samples by using Doppler S-parameter and lifetime measurements. Samples were bombarded with 140keV Ar ions to a dose of 2 x 1013 or 5 x 1016/cm2, respectively, in order to produce disordered or amorphous states in the near-surface regions. The defect-sensitive line-shape S-parameter indicated the presence of small vacancy-like defects in the disordered samples, and higher-order vacancy clusters in amorphous samples. Pulsed positron-beam lifetime results indicated that the disordered samples exhibited a lifetime distribution which could be attributed mainly to divacancies. In the case of amorphous samples, the lifetime distribution was broad; with larger lifetime values that indicated the presence of a distribution of large vacancy clusters or nano-voids. By using published theoretical lifetime values for Si, an empirical fit to the lifetime variation was obtained as a function of the vacancy cluster size. By comparing experimental lifetime distributions with these data, the vacancy cluster size distributions in disordered and amorphous samples could be deduced. In disordered material, divacancies were found to be the predominant defect species, followed by small concentrations of V3. In amorphous material, nanovoids with sizes ranging from 4 to 7 vacancy clusters were present, with V5 and V6 clusters being the predominant defect species.

Identification of Open-Volume Defects in Disordered and Amorphized Si: a Depth-Resolved Positron Annihilation Study. G.Amarendra, R.Rajaraman, G.V.Rao, K.G.M.Nair, B.Viswanathan, R.Suzuki, T.Ohdaira, T.Mikado: Physical Review B, 2001, 63[22], 224112 (6pp)