Positron Annihilation Studies of Czochralski-Grown Silicon Annealed Under Pressure

Abstract

Two positron techniques have been applied to study dynamics of oxygen precipitation in Czochralski-grown silicon, annealed under high (up to 1.4 GPa) pressure. Lifetime measurements were performed with 180 ps resolution; Doppler broadening with a variable-energy slow-positron beam. Different thermal treatings rise the mean lifetime of positrons from 222 ps in as-grown samples up to 227 ps. In samples with a high (up to 85%) amount of oxygen precipitated, an intermediate (550-800 ps) lifetime is observed.

Positronium Formation in Organic Liquids

“…Positron lifetimes are much shorter, 100-200 ps in metals [2] or semiconductors [3]. Tiny (few ps, imposed on 220 ps) differences of positron lifetimes in Czochralski-grown silicon allowed to detect clustering of oxygen atoms around defects [4,5]. In polymers, monitoring o-Ps lifetime (with similar values to those in liquids) became a powerful tool to study phase transitions [6] and dynamics of peristaltic vibrations of the chains [7].…”

Genetic Algorithms for Positron Lifetime Data

“…The total counting rate was about 1.5-2.0 × 10 6 for Mo and 1.1 × 10 6 for Si samples; for the latter case the statistics was improved by performing several independent runs with the same sample [11].…”

“…All samples underwent a double "oxygen-nucleation" treatment, first at 450 • C for 20 h, then 20 h at 650 • C and an additional treatment under high pressure at 870-950 • C. Details of the thermal treatments are given in Ref. [11].…”

“…2) lifetime spectra in high-purity Czochralski-grown silicon (Cz-Si) in which oxygen precipitates were induced by thermal treating at high hydrostatic pressures; our previous analysis of these spectra [11] with POSFIT method [12] indicated presence of nano-voids with lifetimes in a broad range (0.5-1.1 ns)…”