Optical Properties of Ge_<40>Sb_<10>Te_<50>B_x (x=0-2) Films

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Phase-change optical recording media of the base composition Ge_<40>Sb_<10>Te_<50> with or without boron doping (0.3-1.1 at.%) were prepared by rf sputtering on Si(100) substrate at a film thickness 100 nm. Crystalline state was obtained by subsequent annealing at 300℃ for 10 min. The structure study of crystallized films showed that lattice parameter of the fcc Ge_<40>Sb_<10>Te_<50> phase increases slightly with B doping. Crystallization temperature increases manifestly with minor B addition (10℃ at 0.3 at.% B, and 25℃ at 1.1 at.% B). The reflectivity contrast between the crystalline and amorphous states of the undoped Ge_<40>Sb_<10>Te_<50> film ranges from 29% at the wavelength 350 nm to 38% at 800 nm. With an optimal 0.3 at.% B doping, the reflectivity contrast exceeds 40% throughout the whole visible wavelength range. The distinct changes in refractive index and extinction coefficient of the Ge_<40>Sb_<10>Te_<50>B_x films due to crystallization is elucidated and found to be advantageous in obtaining high reflectivity contrast.
社団法人応用物理学会の論文
1999-11-15