Isolated substitutional silver and silver-induced defects in silicon: An electron paramagnetic resonance investigation
Two new electron paramagnetic resonance spectra in silicon doped with silver in a water vapor atmosphere are reported. The observed centers, labeled Si-NL56 and Si-NL57, show a symmetry lower than cubic and an effective electron spin S=1/2. Based on studies with enriched silver isotopes and analysis of the observed two-fold hyperfine splitting, the participation of one silver atom is established for two centers. The Si-NL56 center of the orthorhombic-I symmetry is identified as an isolated substitutional silver atom, and its electronic structure is shown to conform to the vacancy model. Due to the presence of an additional hyperfine interaction with a nuclear spin I=5/2 the Si-NL57 spectrum of the trigonal symmetry is assigned to a complex of silver with another impurity introduced during the diffusion process. Taking into account the sample preparation procedure, the Si-NL57 center is attributed to an Als-Agi pair in a negative charge state. This observation also indicates the diffusion enhancement of aluminum in silicon treated in the water vapor atmosphere.