Point defects in thin HfAlO x films probed by monoenergetic positron beams

Thin HfAlO x films grown on SiON(0.9 nm)/Si by atomic layer deposition technique were characterized by using monoenergetic positron beams. The lifetimes of positrons in the HfAlO x film after post-deposition annealing (PDA) ranged between 412–403 ps. Since these lifetimes were longer than the lifetime of positrons trapped by point defects in metal oxides, such as LaCoO 3 , PbTiO 3 , and BaTiO 3 , the positrons in HfAlO x films were considered to annihilate from the trapped state by open spaces which exist intrinsically in their amorphous structure. The line-shape parameter S of the Doppler broadening spectrum corresponding to the annihilation of positrons in HfAlO x films decreased by PDA, and the S value decreased with increasing an O 2 -content in an atmosphere during PDA (0.004–1%). The observed behavior of the S value was attributed to the shrinkage of the open spaces due to the change in the matrix structure of HfAlO x . After P + - and B + -implantation into poly-Si films grown on the HfAlO x films, the diffusion of positrons in the Si substrates toward the HfAlO x film was suppressed. This fact was attributed to positive charges introduced near the HfAlO x films.