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Surface reactivity enhancement on a Pd/Bi2Te3 heterostructure through robust topological surface states.

He QL, Lai YH, Lu Y, Law KT, Sou IK - Sci Rep (2013)

Bottom Line: We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure.The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation.A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

View Article: PubMed Central - PubMed

Affiliation: William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Hong Kong, SAR China.

ABSTRACT
We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

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XPS Pd 3d5/2 core-level spectra and the resulted amount of oxidized Pd of S#5.(a) and (b) are Pd 3d5/2 core-level spectra obtained from S#5A and S#5B respectively for three regions with Pd coverage of 4, 6 and 8 monolayers. Also shown in each spectrum are the Pd and PdO peaks resulted from standard XPS fitting. (c) Pd coverage dependence of the amount of oxidized Pd of S#5A and S#5B.
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f6: XPS Pd 3d5/2 core-level spectra and the resulted amount of oxidized Pd of S#5.(a) and (b) are Pd 3d5/2 core-level spectra obtained from S#5A and S#5B respectively for three regions with Pd coverage of 4, 6 and 8 monolayers. Also shown in each spectrum are the Pd and PdO peaks resulted from standard XPS fitting. (c) Pd coverage dependence of the amount of oxidized Pd of S#5A and S#5B.

Mentions: To investigate the Pd-thickness dependence of the enhancement of the surface reactivity of the Pd/Bi2Te3 heterostructure, XPS analysis was performed on S#5, which is a Pd/Bi2Te3 heterostructure containing 3 regions with Pd coverage of 4, 6 and 8 monolayers. An as-prepared piece of this sample (S#5A) was quickly transferred to the XPS system and another piece was kept in dry air for 3 days (S#5B) prior to performing the XPS measurement. A standard data fitting for the resulted Pd 3d5/2 spectra was carried out to resolve the core-level peaks into Pd and PdO components (see Fig. 6). As the PdO layer always locates on the top surface, the area of the PdO components obtained from the fitting results of the XPS spectra can be taken as a good approximation of the amount of the oxidized Pd. Fig. 6 displays the resulted amount of the oxidized Pd versus the Pd coverage for S#5A and S#5B. If the oxidation of the Pd layers is purely native, one should expect the amount of this oxide would not depend on the coverage of Pd. However, as can be seen in Fig. 6(c), both samples show a consistent descending trend for the amount of PdO as the Pd coverage increases, which can be regarded as a signature of the electron bath effect from the TSSs, as one would expect that this effect should normally weaken for a thicker Pd layer in this heterostructure.


Surface reactivity enhancement on a Pd/Bi2Te3 heterostructure through robust topological surface states.

He QL, Lai YH, Lu Y, Law KT, Sou IK - Sci Rep (2013)

XPS Pd 3d5/2 core-level spectra and the resulted amount of oxidized Pd of S#5.(a) and (b) are Pd 3d5/2 core-level spectra obtained from S#5A and S#5B respectively for three regions with Pd coverage of 4, 6 and 8 monolayers. Also shown in each spectrum are the Pd and PdO peaks resulted from standard XPS fitting. (c) Pd coverage dependence of the amount of oxidized Pd of S#5A and S#5B.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750537&req=5

f6: XPS Pd 3d5/2 core-level spectra and the resulted amount of oxidized Pd of S#5.(a) and (b) are Pd 3d5/2 core-level spectra obtained from S#5A and S#5B respectively for three regions with Pd coverage of 4, 6 and 8 monolayers. Also shown in each spectrum are the Pd and PdO peaks resulted from standard XPS fitting. (c) Pd coverage dependence of the amount of oxidized Pd of S#5A and S#5B.
Mentions: To investigate the Pd-thickness dependence of the enhancement of the surface reactivity of the Pd/Bi2Te3 heterostructure, XPS analysis was performed on S#5, which is a Pd/Bi2Te3 heterostructure containing 3 regions with Pd coverage of 4, 6 and 8 monolayers. An as-prepared piece of this sample (S#5A) was quickly transferred to the XPS system and another piece was kept in dry air for 3 days (S#5B) prior to performing the XPS measurement. A standard data fitting for the resulted Pd 3d5/2 spectra was carried out to resolve the core-level peaks into Pd and PdO components (see Fig. 6). As the PdO layer always locates on the top surface, the area of the PdO components obtained from the fitting results of the XPS spectra can be taken as a good approximation of the amount of the oxidized Pd. Fig. 6 displays the resulted amount of the oxidized Pd versus the Pd coverage for S#5A and S#5B. If the oxidation of the Pd layers is purely native, one should expect the amount of this oxide would not depend on the coverage of Pd. However, as can be seen in Fig. 6(c), both samples show a consistent descending trend for the amount of PdO as the Pd coverage increases, which can be regarded as a signature of the electron bath effect from the TSSs, as one would expect that this effect should normally weaken for a thicker Pd layer in this heterostructure.

Bottom Line: We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure.The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation.A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

View Article: PubMed Central - PubMed

Affiliation: William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Hong Kong, SAR China.

ABSTRACT
We present a study of the surface reactivity of a Pd/Bi2Te3 thin film heterostructure. The topological surface states from Bi2Te3, being delocalized and robust owing to their topological natures, were found to act as an effective electron bath that significantly enhances the surface reactivity of palladium in the presence of two oxidizing agents, oxygen and tellurium respectively, which is consistent with a theoretical calculation. The surface reactivity of the adsorbed tellurium on this heterostructure is also intensified possibly benefitted from the effective transfer of the bath electrons. A partially inserted iron ferromagnetic layer at the interface of this heterostructure was found to play two competing roles arising from the higher-lying d-band center of the Pd/Fe bilayer and the interaction between the ferromagnetism and the surface spin texture of Bi2Te3 on the surface reactivity and their characteristics also demonstrate that the electron bath effect is long-lasting against accumulated thickness of adsorbates.

Show MeSH
Related in: MedlinePlus