Doping effect on optical recording film with Ge2Sb2Te5 composition

In stoichiometric GeTe-Sb2Te3 films, reversible phase change optical recording materials, Sb addition is used widely to improve the data retention time and the repetition cycles, but its mechanism is not clear. To clarify the effect of excess Sb, the effects of Te and Ge addition were also investigated in the compositions from the stoichiometry Ge2Sb2Te5 toward the vertices in the Ge-Te-Sb triangle. By DSC measurements, it was found that a retention ability for amorphous (`write') states related to the increase of repetition cycles is larger in the Sb addition than in the Te and Ge addition. By XRD measurements, it was understood that an optimum ratio of (Sb,Te)(beta) /GeTe(111), about 0.5 was necessary to static repetition cycles approximately 106 in the laser annealed film of 1000 angstroms thick.