Thermal behavior of metal layers sandwiched by silicon dioxide layers

Abstract

The diffusion of metal particles into a silicon oxide layer during chemical vapor deposition causes various carbon nanotube growth modes. Here, the diffusion behavior of Co and Fe layers sandwiched between silicon oxides was investigated. The Co layer does not diffuse, while the Fe layer diffuses when annealed in Ar/H 2 . The thermal behavior also depends on the ambient gas. The diffusivity of Fe and the nondiffusivity of Co when annealed in Ar/H 2 can be explained by ionic radius and valence requirements. Fe 3+ , which has a similar ionic radius to Si 4+ , can thermally diffuse via the substitution of Si 4+ at the center of SiO 4 tetrahedra with an oxygen vacancy, whereas Co 2+ does not diffuse through substitution owing to its larger ionic radius and strict requirements for two oxide vacancies in SiO 4 tetrahedra.

EELS Study of Differential Diffusion of Fe and Co in Magnetized Silica Nanocomposites

“…STEM images of spherical CoFe 2 O 4 /SiO 2 nanocomposites obtained at the annealing temperatures of 430 °C (Figure a), 500 °C (Figure b), 600 °C (Figure c), and 700 °C (Figure d) indicate hollow interiors, with Co-rich CoFe 2 O 4 phase at 500 °C based on EDS analysis (Figure g). Compared to Fe 3+ , Co 2+ is known more reluctant to replace vacant sites of tetrahedral Si mainly due to its large ionic size . Co 2+ is also known to be not reactive with SiO 2 or metallic Si.…”

“…Compared to Fe 3+ , Co 2+ is known more reluctant to replace vacant sites of tetrahedral Si mainly due to its large ionic size. 44 Co 2+ is also known to be not reactive with SiO 2 or metallic Si. It mostly resides on the surface of SiO 2 and forms localized clusters until its growth to crystalline CoFe 2 O 4 , 45 while Fe is known to diffuse into metallic Si 46 In the formation of Fe 3 O 4 , diffusion of cations within Fe 3 O 4 is fast and the formation is easy, but with accompanying cation vacancies.…”

High-temperature resistant interconnection using Ni nanoparticles and Al microparticles paste sintered in an atmosphere

“…[1][2][3][4][5][6][7][8] Power devices that use wide bandgap semiconductors can operate at temperatures higher than those of conventional Si power devices, and power devices that operate in an operating environment of 200 °C-250 °C are being developed in the automotive field with benefits such as downsizing of the cooling system. [9][10][11] Furthermore, it is expected to operate in high-temperature environments exceeding 500 °C in aircraft, space-related fields, gas and oil mining/underground exploration, nuclear equipment, etc. 12,13) When mounting power devices, an Sn-Ag-Cu solder is mainly used as a die-bonding material in conventional structures using Si semiconductors.…”