An XPS depth-profile study on electrochemically deposited TaO x

Abstract

Through the use of XPS and controlled Ar + etching, the surface composition and oxide species of tantalum oxides (TaO x ), which were electrodeposited on glassy carbon electrodes by cyclic voltammetric and constant-potential electrolyses, are quantified along the depth profile. Electrodeposition exhibits efficacy in depositing TaO x with a distribution of various TaO x : TaO, TaO 2 , and Ta 2 O 5 . The distribution gradient from the outer surface of TaO x is such that Ta 2 O 5 > TaO 2 >TaO. TaO is found to be the dominant species in the underlying layer of TaO x . Such a unique structure of the electrode surface is analogous to that of nanoparticles with a core-shell structure, with the core being suboxides and the surface being that of the saturated pentoxide, Ta 2 O 5 . The electrochemically induced nonhydrolytic condensation route is proposed to be capable of producing TaO x with a distribution gradient of Ta 2 O 5 , TaO 2 , and TaO in the depth direction.

Morphological Effects and Stabilization of the Metallic 1T Phase in Layered V‐, Nb‐, and Ta‐Doped WSe2 for Electrocatalysis

“…Likewise, the main Nb 3d 5/2 and Nb 3d 3/2 binding energies in Nb‐doped WSe 2 at approximately 207.8 and 210.6 eV are characteristic of the Nb 5+ species . Ta‐doped WSe 2 shows a primary Ta 4f signal at Ta 4f 7/2 and Ta 4f 5/2 binding energies of approximately 27.2 and 29.1 eV, which originate from the Ta V state …”

“…It is also noteworthy to mention that aside from the principal pentavalent species detected in the Group 5 transition‐metal dopants, a considerable portion of the deconvoluted states suggest the coexistence of the other valence states. Most prominently, the shoulder signal manifested by the Ta‐doped WSe 2 corresponds to the Ta II state with Ta 4f 7/2 and Ta 4f 5/2 binding energies at approximately 24.1 and 26.1 eV . The Ta II and Ta V states in Ta‐doped WSe 2 are equally dominant.…”

Tuning Up or Down the Critical Thickness in LaAlO3/SrTiO3 through In Situ Deposition of Metal Overlayers

“…Thin film growth. The LaAlO3 (LAO) films were grown by PLD on 5 mm  5 mm TiO2- [28] . No Ta metal peak is discernable (usually Submitted to 17 located 5 eV away from the oxide peak) which indicates that the Ta capping is nearly fully oxidized.…”

Transition Metal Carbide Core/Shell Nanoparticles by Ultra-Short Laser Ablation in Liquid

“…In fact, in the Ta4f 7/2 signal of acetone mediated particles (Figure 2a(III)) presents a shoulder at lower BE with respect to the Ta 2 O 5 component. This shoulder, centered at 24.9 eV can be related to suboxide tantalum species [33]. The component at 23.1 eV confirms the presence of tantalum carbide, with a Ta 4 C 3 stoichiometry.…”