First-principles study of carbon impurity effects in the pseudo-hexagonal Ta2O5

Abstract

Carbon-impurity effects on electronic structures and oxygen-vacancy formation stability of Ta 2 O 5 resistive memories are investigated using the density-functional theory. Generalized gradient approximation with on-site Coulomb corrections is employed for the investigation. The unintentionally incorporated carbon can cause unwanted increase in the resistive off-state leakage current by extending the defect state region in the bandgap. The carbon impurities are found to be preferentially located in the neighborhood of the oxygen vacancies, and they reduce the oxygen-vacancy formation energy, which is predicted to have an influence on lowering the forming voltage.

Effect of ion bombardment on the chemical properties of crystalline tantalum pentoxide films

“…These patterns can be indexed to the orthorhombic phase β−Ta 2 O 5 (PDF 00-025-0922 with lattice parameters a = 6.1980 Å, b = 40.2900 Å, c = 3.8880 Å, and α = β = γ = 90 • for the spatial group P 2 1 2 1 2). We stress that there is still an ongoing discussion regarding the specific space group for the crystalline phases of Ta 2 O 5 17,18,31,[40][41][42][43][44][45] .…”

Influence of post-deposition annealing on the chemical states of crystalline tantalum pentoxide films

“…It is evident that F1273 exhibits a series of small reflections along the whole pattern that match the reference pattern PDF 025-0922. It is important to underline that so far there has not been a consensus regarding the spatial symmetry of these two phases, and, due to the overlapping of several peaks, one cannot rule out the coexistence of both phases 21,[29][30][31][32][33][34][35][36] .…”

“…It is evident that F1273 exhibits a series of small reflections along the whole pattern that match the reference pattern PDF 025-0922. It is important to underline that so far there has not been a consensus regarding the spatial symmetry of these two phases, and, due to the overlapping of several peaks, one cannot rule out the coexistence of both phases 21,[29][30][31][32][33][34][35][36] . To the best of our knowledge, at least 12 spatial groups has been proposed and we do think it is not worth computing the lattice parameters or conducting a Rietveld refinement, since these depend on the particular choice of the group symmetry.…”

Evidence for structural transition in crystalline tantalum pentoxide films grown by RF magnetron sputtering

“…These patterns can be indexed to either the orthorhombic phase β−Ta 2 O 5 (PDF 00-025-0922 with lattice parameters a = 6.1980Å, b = 40.2900Å, c = 3.8880Å, and α = β = γ = 90 • for the spatial group P 2 1 2 1 2; or PDF 01-089-2843 with lattice parameters a = 6.2000Å, b = 3.6600Å, c = 3.8900 A, and α = β = γ = 90 • for the spatial group Amm2) or the hexagonal phase δ−Ta 2 O 5 (PDF 00-019-1299 with lattice parameters a = b = 3.6240Å, c = 3.8800Å, α = β = 90 • , and γ = 120 • , with presumably spatial group P 6/mmm 23,24 ). As of now, there is still an ongoing debate regarding the specific space group of these two phases 15,16,[25][26][27][28][29] . According to our results, it is clear that as the annealing temperature is raised more peaks in the diffraction patterns show up.…”

“…These patterns can be indexed to either the orthorhombic phase β−Ta group P 6/mmm 23,24 ). As of now, there is still an ongoing debate regarding the specific space group of these two phases 15,16,[25][26][27][28][29] . According to our results, it is clear that as the annealing temperature is raised more peaks in the diffraction patterns show up.…”