Identification of intrinsic electron trapping sites in bulk amorphous silica from ab initio calculations

AM El-Sayed and MB Watkins and AL Shluger and VV Afanas'ev, MICROELECTRONIC ENGINEERING, 109, 68-71 (2013).

DOI: 10.1016/j.mee.2013.03.027

Using ab initio calculations we demonstrate that extra electrons in pure amorphous SiO2 can be trapped in deep band gap states. Classical potentials were used to generate amorphous silica models and density functional theory to characterise the geometrical and electronic structures of trapped electrons. Extra electrons can trap spontaneously on pre-existing structural precursors in amorphous SiO2 and produce approximate to 3.2 eV deep states in the band gap. These precursors comprise wide (>= 130 degrees) O-Si-O angles and elongated Si-O bonds at the tails of corresponding distributions. The electron trapping in amorphous silica structure results in an opening of the O-Si-O angle (up to almost 180 degrees). We estimate the concentration of these electron trapping sites to be approximate to 5 x 10(19) cm(-3). (C) 2013 Elsevier B.V. All rights reserved.

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