Diffusion of Sr, Bi, and Ta in amorphous SiO2

Abstract

Diffusion of Sr, Bi, and Ta in SiO 2 was studied to determine diffusion coefficients and diffusion mechanisms of these elements in the amorphous material. Technological motivation is the introduction of strontium bismuth tantalate (SBT) as ferroelectric material for nonvolatile memories. Diffusion from an SBT layer into a thin layer of SiO 2 was promoted by annealing at 800 C for times ranging from 1 to 24 h: Concentration profiles of the diffusing elements in the SiO 2 layer were recorded by secondary ion mass spectroscopy (SIMS). The measured profiles were compared to profiles derived from calculations for different diffusion mechanisms. The theoretical profile best matching the form of the measured profile was fitted to the experimental data, yielding information about the diffusion mechanism and the diffusion coefficient. The diffusion coefficient of Sr is in the range of 10 À15 cm 2 =s at 800 C and 10 À14 cm 2 =s for Bi. It was found out that Sr and Bi react with vacancies in the SiO 2 ; forming fast-moving complexes. Tantalum shows no measurable diffusion in this time and temperature range. No information is available about the exact nature of the different Sr and Bi species, since SIMS can only detect elements but not their binding situation. Only indirect indications lead to the theory that vacancies play a role in the transformation from slow-to fast-moving species. Theoretical calculations of the behavior of the elements in SiO 2 may help to solve this problem. r

The difference of PMMA‐brush‐modification on the oxygen permeable perovskite‐type oxides by consisting elements

“…Moreover Si forms silicates with various metals. 33,34 We confirmed the formation of strontium silicate in a sintered mixture of LSCF1991 and SiO 2 at 1250°C (Figure S1-S3). Therefore, the cations near the particle surface might react with Si, breaking and changing the perovskite-type structure into an oxide like silicate, which had low oxygen desorption.…”

Influence of Ta content on the physical properties of SrBi2Ta2O9 ferroelectric thin films

“…Because the Ta-O bonding strength is greater than those of Sr-O and Bi-O bonds, the diffusion coefficient of Ta (<10 −17 cm 2 /s) in SBT is much lower than those of the Sr (10 −15 cm 2 /s) and Bi (10 −14 cm 2 /s) atoms, as measured from the SBT species in a SiO 2 layer at 800°C. 26 We believe that the diffusion behavior of SBT in our present study is controlled by the constituted Ta ions and is accelerated significantly by the generation of Ta +5 vacancies. Therefore, both the nucleation and growth of the BLS grains in Ta18 would be promoted by the deficiency of Ta ions in the material.…”

Thermally stable perpendicular magnetic anisotropy features of Ta/TaOx/Ta/CoFeB/MgO/W stacks via TaOx underlayer insertion

“…4(a), the Ta seed layer (orange dots) in Sample A is placed directly on the Si/SiO 2 substrate, where the thermally oxidized SiO 2 layer is known to have a primarily firm and rigid phase for Ta diffusion. 16 Post-thermal treatment drives thermally activated Ta atoms (gray dots) to diffuse mainly toward the CoFeB layer (yellow dots) via an exchange diffusion mechanism between Ta and B atoms, where the relatively easy drift of B atoms into the solid occurs due to their unstable bonds with Co and Fe atoms. 18 Consequently, thermal treatment above a particular temperature (in this paper, 350 C) favors the presence of Ta atoms at the CoFeB/MgO interface or MgO regions.…”