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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ta5Si3 by Materials Project

Ta5Si3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 5-coordinate geometry to five equivalent Si atoms. There are a spread of Ta–Si bond distances ranging from 2.60–2.87 Å. In the second Ta site, Ta is bonded in a 6-coordinate geometry to six equivalent Si atoms. All Ta–Si bond lengths are 2.66 Å. Si is bonded in a 9-coordinate geometry to nine Ta atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta5Si3 by Materials Project

Ta5Si3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Ta–Si bond distances ranging from 2.61–2.73 Å. In the second Ta site, Ta is bonded to six Si atoms to form distorted corner-sharing TaSi6 octahedra. The corner-sharing octahedra tilt angles range from 0–51°. There are four shorter (2.57 Å) and two longer (2.98 Å) Ta–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 10-coordinate geometry to ten Ta atoms. In the second Si site, Si is bonded in a 9-coordinate geometry to eight Ta and one Si atom. The Si–Si bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta5Si3 by Materials Project

Ta5Si3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Ta sites. In the first Ta site, Ta is bonded in a 6-coordinate geometry to six Si atoms. There are a spread of Ta–Si bond distances ranging from 2.65–2.94 Å. In the second Ta site, Ta is bonded in a 6-coordinate geometry to two equivalent Ta and four equivalent Si atoms. Both Ta–Ta bond lengths are 2.55 Å. All Ta–Si bond lengths are 2.67 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 10-coordinate geometry to ten Ta atoms. In the second Si site, Si is bonded in a 10-coordinate geometry to eight equivalent Ta and two equivalent Si atoms. Both Si–Si bond lengths are 2.55 Å.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Thermal fatigue behavior of H-13 die steel for aluminum die casting with various ion sputtered coatings

Sputtered coatings of Mo, W, Pt, Ag, Au, Co, Cr, Ni, Ag + Cu, Mo + Pt, Si3N4, A1N, Cr3C2, Ta5Si3, and ZrO2 were applied to a 2-inch-square, 7-inch-long thermal fatigue test specimen which was then internally water cooled and alternately immersed in molten aluminum and cooled in air. After 15,000 cycles the thermal fatigue cracks at the specimen corners were measured. Results indicate that a significant improvement in thermal fatigue resistance was obtained with platinum, molybdenum, and tungsten coatings. Metallographic examination indicates that the improvement in thermal fatigue resistance resulted from protection of the surface of the die steel from oxidation. The high yield strength and ductility of molybdenum and tungsten contributed to the better thermal fatigue resistance.

Nieh, C. Y.↗
NASA NTRS1980

Adherence of ion beam sputter deposited metal films on H-13 steel

An electron bombardment argon ion source sputter deposited 17 metals and metal oxides on H-13 steel. The films ranged 1 to 8 micrometers in thickness and their adherence was generally greater than the capacity of the measuring device; adherence quality depended on proper precleaning of the substrate before deposition. N2 or air was introduced for correct stoichiometry in metallic compounds. Au, Ag, MgO, and Ta5Si3 films 8 microns thick have bond strength equal to 1 micron coatings; the bond strength of pure metallic films up to 5 microns thick was greater than the epoxy to film bond (8000 psi). The results of exposures of coated material to temperatures up to 700 C are presented.

Mirtich, M. J.↗
NASA NTRS1991

Sputtered Ta-Si-N diffusion barriers in Cu metallizations for Si

Electrical measurements on shallow Si n+-p junction diodes with a 30-nm TiSi2 contacting layer demonstrate that an 80-nm-thick amorphous Ta36Si14N50 film prepared by reactive RF sputtering of a Ta5Si3 target in an Ar/N2 plasma very effectively prevents the interaction between the Si substrate with the TiSi2 contacting layer and a 500-nm Cu overlayer. The Ta36Si14N50 diffusion barrier maintains the integrity of the I-V characteristics up to 900 C for 30-min annealing in vacuum. It is concluded that the amorphous Ta36Si14N50 alloy is not only a material with a very low reactivity for copper, titanium, and silicon, but must have a small diffusivity for copper as well.

Kolawa, E.↗
NASA NTRS1994

Reaction of Ta thin film with single crystalline (001) beta-SiC

The reaction between a sputtered-deposited Ta film (320 nm thick) and a single crystalline (001) beta-SiC substrate induced by vacuum annealing at temperatures of 600-1200 C for 1 h (30 min at 1100 C) is investigated by 3 MeV He(+2) backscattering spectrometry, x-ray diffraction, secondary ion mass spectrometry, and transmission and scanning electron microscopies. No significant reaction is observed at 800 C or at lower tempertures. At 900 C, the main product phases are Ta2C and carbon-stabilized Ta5Si3. A minor amount of unreacted Ta is also present. After annealing at 1000 C, all the tantalum has reacted; the reaction zone possesses a multilayered structure of beta-SiC/TaC/carbon-stabilized Ta5Si3/alpha-Ta5Si3/Ta2C. The diffusion path at 1000 C is plotted on the isothermal section of the Ta-Si-C phase diagram. At 1100 C, the reacted layer has an interface with the SiC substrate that is still quite flat but has a rough surface due to the formation of macroscopic voids within the reacted layer. The equilibrium products predicted by the phase diagram are TaC and TaSi2. This final state is reached by annealing at 1200 C for 1 h. At that point, the reacted layer has a latterally very uneven structure and morphology.

Chen, J. S.↗