Formation of electron traps in amorphous silica

The capture of an electron by a silicon atom in a defect-free bulk of amorphous silica (a-SiO(2)) has been investigated. Ab initio constrained dynamics has been applied to evaluate the energy barrier. The computed energy barrier involved in the mechanism was found to be 0.23 eV. The electron trapping is accompanied by a strong local distortion of the tetrahedron of Si and O involved in the process. Hydrogen, which is an electronically active impurity of silicon dioxide, bonds to the oxygen of the Si-O silica bond on which the electron is localized. Upon restoring the neutrality of the system a paramagnetic configuration is found. The eigenvalues of the hyperfine tensor have been evaluated.