Grazing Incidence X-ray Study Of Ge-nanoparticle Formation In (ge:sio_2)/sio_2 Multilayers

摘要

We present the study of formation of Ge-nanoparticles (Ge-NP) in germanosilicate (Ge:SiO_2) multilayer (ML) films under thermal treatment. In anticipation of controllable formation of Ge-NP, ML films were prepared by magnetron deposition at room temperature as 20 bi-layer stacks, each bi-layer comprised of a 7 nm thick layer of (Ge + SiO_2) (molar ratio: 60:40) succeeded by a 7 nm thick layer of pure SiO_2, and then annealed for 1 h, up to T_a = 900 ℃. Formation and morphology of Ge-NP were analyzed by combining the information obtained from the grazing incidence small angle X-ray scattering and X-ray diffraction. It was found that precipitation of Ge-NP starts at T_a = 600 ℃, while high degree of in-plane confinement and lateral ordering of rather uniform precipitated particles is achieved at T_a = 700-800 ℃ range. At still higher annealing temperature T_a > 800 ℃, volume fraction of precipitated Ge-NP in SiO_2 matrix diminishes due to the out-diffusion of Ge atoms from the film, while Ge-NP are no more well confined to (Ge + SiO_2) layers.