In situ observation of iron atoms in multicrystalline silicon at 1273 and 300 K by Mössbauer spectroscopy

Abstract

57Fe Mössbauer absorber experiments are performed at 1273 and 300 K on two different samples of multicrystalline Si (mc-Si), whose minority carrier lifetimes are 41 and 1.5 μs, respectively. The samples are deposited with 1.5 nm 57Fe, and are annealed and measured simultaneously at 1273 K for 1 week. The spectra consist of four singlets at 1273 K, and of three singlets at 300 K. Comparing the present results with those from 57Fe-deposited CZ-Si single crystal, the 57Fe atoms are found to exist in the mc-Si matrix dominantly as substitutional Fe atoms and different Fe-defect clusters, but not as FeSi 2 precipitates. One of the components at 1273 K, which yields an isomer shift of 1.1 mm s −1, appears to be due to interstitial Fe atoms trapped on defects. The fraction depends clearly on the minority carrier lifetime, and therefore, on the quality of the mc-Si samples.