Crystallization characteristics of Ge-doped Sb70Te30 phase change recording film

Due to the fast development of multi-media technology, the demand of larger recording capacity and faster data transfer rate media is getting higher. The increase of recording capacity can be achieved by reducing the wavelength of laser pick-up or increasing the numerical aperture of object lens. To speed up data transfer rate, fast crystallization phase change material is required. Eutectic Sb₇₀Te₃₀ fast-growth material is one of the promising candidates for high data transfer rate recording (H.J. Borg et al, ISOM/ODS´99, Proc. SPIE vol. 3864, p. 191, 1999; H.J. Borg et al, ISOM2000, p. 6, 2000). However, it also shows the disadvantage of poor thermal stability (H.J. Borg et al, Jpn. J. Appl. Phys. vol. 40, pp. 1592-1597, 2001). An effective way to solve this problem is doping specific elements into the Sb₇₀Te₃₀ fast-growth material. Germanium with high value of T_g/T_m is expected to play the role of thermal stabilizer (M.Okuda et al, Jpn. J. Appl. Phys. vol. 31, p. 466, 1992). In this paper, we quantitatively study the effects of Ge doping on the optical properties and crystallization characteristics of Sb₇₀Te₃₀ recording film.