Preparation and Characterization of a New Ge-Sb-Te Thin Film

Ge₁₀Sb_67.5Te_22.5 thin films were prepared by RF magnetron sputtering from a single high purity Ge₁₀Sb _67.5Te_22.5 target under the following condition: RF power: 30 W, Ar pressure: 1.067 Pa, Ar flow: 9 ccm, substrate temperature: room temperature (water cooling), distance between target and substrate: 7 cm, and sputtering time: 10∼40 min. Although the as-deposited film was amorphous, annealing for 30 min at 573 K allowed it to be crystallized. The crystallization temperature and the activation energy of Ge₁₀Sb _67.5Te_22.5 thin film were around 463 K and 2.50 eV, respectively, while those of Ge₂Sb₂Te₅ thin film, prepared under the same conditions as stated above, were around 408 K and 2.04 eV, respectively. The difference of optical constants between crystalline and amorphous phases of Ge₁₀Sb_67.5Te_22.5 and Ge₂Sb₂Te₅ thin films were -0.9 + i0.93 and -0.77 + i0.67, respectively, in a blue laser area, i.e., wavelength 405 nm.