New paramagnetic center in amorphous silicon doped with rare-earth elements

A new paramagnetic center associated with rare earths (RE) (La, Ce, Pr, Nd, Gd, Er, and Lu) in amorphous silicon is reported. It is shown that RE impurities are incorporated in a-Si and that the density of paramagnetic dangling bonds decreases as a consequence of the presence of these impurities. An interpretation in terms of RE $6s$ orbitals and crystal-field-split $5d$ orbital hybridization suggests that the RE behaves as an acceptor impurity with an associated hole in the a-Si valence-band tail, which is responsible for the observed resonance at a g value of 2.10±{}0.01.