XPS study of polycrystalline and epitaxial FeTaN films deposited by d.c. reactive magnetron sputtering

Yang, Dehua; Jiang, H.; Ott, Ronald D; Minor, K.; Grant, Jonathan; Varga, L.K.; Barnard, J. A.; Doyle, William

doi:10.1002/(sici)1096-9918(199904)27:4<259::aid-sia560>3.0.co;2-n

Cited by 6 publications

(9 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistent with the in situ XPS, the post-growth signature of SiO 2 supported thin Ta-oxide only shows peaks corresponding to Ta-oxides (Ta4f 7/2 at y26.2 eV), while no peaks corresponding to Ta-metal (Ta4f 7/2 y22 eV) and -carbide (Ta4f 7/2 y23.3 eV) are found. 43,52,[55][56][57] The post growth C1s signature shows sp 2 -bound carbon (C1s y284.5 eV), in agreement with the SEM observations of grown nanotubes (Fig. 1(a), left).…”

Section: Resultssupporting

confidence: 86%

“…In their as-deposited state (after air exposure), the films show only peaks corresponding to Ta-oxides (Ta4f 7/2 at 26.2 ¡ 0.2 eV). 43,52,[55][56][57] As expected for very thin Ta films after ambient air exposure, 33,52 oxidation of the entire films is confirmed and no peaks corresponding to Ta-metal (Ta4f 7/2 y22 eV) or Ta-carbide (Ta4f 7/2 y23.3 eV) are found. 43,52,[55][56][57] When heated in vacuum, the thin Ta-oxide on SiO 2 support does not change its chemical state, i.e., it stays oxidised even at 850 uC (Fig.…”

Section: Resultssupporting

confidence: 54%

“…The additional peaks can be attributed to Ta-carbide (where the y284.5 eV signal in the C1s region is attributed to graphitic fragments as no nanotube were grown at 900 uC on Al 2 O 3 ). 43,52,[55][56][57] The admixture of Al/Al 2 O 3 to Ta-oxides is known to change the oxides' structural evolution with temperature 62,63 and may lower the temperature for partial Ta-oxide reduction. 64 This could relate to the observed carbide formation here.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Tantalum-oxide catalysed chemical vapour deposition of single- and multi-walled carbon nanotubes

et al. 2013

View full text Add to dashboard Cite

Ta-oxide thin films are shown to catalyse carbon nanotube growth by chemical vapour deposition. A low film thickness, the nature of the support material (best results with SiO2) and an atmospheric process gas pressure are of key importance for successful nanotube nucleation. Strong material interactions, such as silicide formation, inhibit nanotube growth. In-situ X-ray photoelectron spectroscopy indicates that no catalyst reduction to a metal or carbide occurs during nanotube growth and that the catalytically active phase is the Ta-oxide phase. Such a reductionfree oxide catalyst can be advantageous for integration of nanotubes into electronics

show abstract

Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Tantalum-oxide catalysed chemical vapour deposition of single- and multi-walled carbon nanotubes

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Additionally, a small Ta suboxide contribution emerges again which might point to structural rearrangement in the Ta oxide film.) We note that we do not observe XPS peak shifts associated with alloying of the Fe and the Ta, 44 as we did for metallic Fe and metallic Ta under similar conditions. 39 This indicates that the reduced Fe and the Ta oxide do not undergo intimate mixing.…”

Section: Resultsmentioning

confidence: 99%

Co-Catalytic Solid-State Reduction Applied to Carbon Nanotube Growth

et al. 2011

View full text Add to dashboard Cite

We report on a new class of cocatalysts for the chemical vapor deposition of carbon nanotubes, where the cocomponent (Ta) acts as a solid-state reducing agent for the active catalyst (Fe). The cocatalytic FeTa system enables carbon nanotube growth without the need for a reducing gas atmosphere such as H2 or NH3. In situ X-ray photoelectron spectroscopy reveals that the tantalum (oxide) getters the oxygen from the iron (oxide) by a diffusive solid-state process, driven by the much larger affinity to oxygen of Ta compared to Fe. We suggest that this redox-based mechanism is applicable to a wide range of metal (oxide)/catalyst systems and relevant to rational catalyst design in general heterogeneous catalysis

show abstract

“…52,55 During continued exposure, the graphitic sp 2 component grows significantly in intensity with only minor carbide and sp 3 contributions remaining, implying the growth of CNTs (confirmed by postgrowth SEM analysis, showing a low CNT yield corresponding to our AP-CVD results at similar temperatures). The (alloyed) Ta transforms to Ta-carbide (23.5 eV) 51,56 with some Ta-oxide remaining (Figure 11). The Fe exhibits a small shift to 707.2 eV, which points toward stronger interactions between the now carbidic Ta surface and the Fe.…”

Section: Ppt-cvdmentioning

confidence: 99%

Support−Catalyst−Gas Interactions during Carbon Nanotube Growth on Metallic Ta Films

et al. 2011

View full text Add to dashboard Cite

We present a detailed study of processes and interactions occurring during the Fe-catalyzed chemical vapor deposition of carbon nanotubes on metallic Ta supports. In situ X-ray photoemission spectroscopy and X-ray diffraction show that the Fe catalyst increases the reactivity of Ta toward oxidation and carbide formation, whereas Ta promotes the reduction of Fe. This causes an unusual temperature dependence of carbon nanotube growth, where at low temperatures (∼550 °C) vertically aligned forests of carbon nanotubes with ohmic contacts grow readily on metallic Ta, whereas at high temperatures (>600 °C) nanotube growth is sparse because of the diffusion of Fe away from the surface through grain boundaries of in situ formed polycrystalline Ta2O5. The Fe−Ta model system highlights general material selection criteria for nanotube applications that require a conductive support.

show abstract

XPS study of polycrystalline and epitaxial FeTaN films deposited by d.c. reactive magnetron sputtering

Cited by 6 publications

References 34 publications

Tantalum-oxide catalysed chemical vapour deposition of single- and multi-walled carbon nanotubes

Tantalum-oxide catalysed chemical vapour deposition of single- and multi-walled carbon nanotubes

Co-Catalytic Solid-State Reduction Applied to Carbon Nanotube Growth

Support−Catalyst−Gas Interactions during Carbon Nanotube Growth on Metallic Ta Films

Contact Info

Product

Resources

About