Relationship between Ta Oxidation State and Its Local Atomic Coordination Symmetry in a Wide Range of Oxygen Nonstoichiometry Extent of TaO_x

Abstract

Evolution of electronic and atomic structure of amorphous Ta 2 O 5 during sputtering by Ar + ions was investigated by means of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. XPS Ta 4f spectra were analyzed through spectral decomposition by paying special attention to inelastic scattered electron background subtraction from the Ta 4f spectra. The decomposition revealed the formation of Ta 4+ , Ta 3+ , Ta 2+ , Ta + , and Ta 0 chemical states during the sputtering. The dynamics of the Ta chemical states evolution was analyzed and referred to the modification of the local atomic structure revealed by the NEXAFS O K-edge absorption spectra analysis. The transformation of the O K-edge spectra during the sputtering suggests the preservation of a significant part of octahedrons (the structural units of stoichiometric amorphous Ta 2 O 5 ), which serve as a matrix for low-symmetry structural units transformed from the octahedra during the sputtering. Possible mechanisms of the octahedra transformation were discussed based on the O K-edge spectra and orbital correlation diagrams. It is noteworthy that the experiment showed a possibility of complete Ta metallization by Ar + ion bombardment of amorphous Ta 2 O 5 on the Si substrate.

Bifunctional Device with High‐Energy Storage Density and Ultralow Current Analog Resistive Switching

“…But multiple states can be found for the inner of the TaO x film from the peaks of Ta 4f 7/2 (26.68, 24.88, 23.8, and 22.26 eV corresponding to Ta 5+ , Ta 3+ / Ta 4+ , Ta 2+ , and Ta 1+ , respectively). [ 36 ] It implies the existence of substoichiometric tantalum oxide in the film inner.…”

Stoichiometry and disorder influence over electronic structure in nanostructured VOx films

“…In order to confirm this observation, and since the e * g orbitals are the most involved, we investigated V L edges line shape of the NS VO 2 sample (Zaanen et al 1985;Kasatikov et al 2019). Several simulations were carried out within the charge transfer multiplet framework to investigate possible distortions effect on the VO 2 electronic structures.…”

“…The observed e * g red-shift in the NS-VO 2 is possibly due to the presence of Jahn-Teller-like distortions of the oxygen octahedron matrix which directly influences the electronic structure of the NS sample (Kasatikov et al 2019;Ruzmetov et al 2007). In the extreme case, a high number (ideally infinite) of different ligand distortions coexist withi n a disordered material.…”

Role of an Interfacial Layer in Ta2O5‐Based Resistive Switching Devices for Improved Endurance and Reliable Multibit Operation

“…The binding status of Ta4f 7/2 was maintained near the Pt TE region in the Pt/Ta 2 O 5 /Pt stacked RS device, indicating that an interfacial layer did not form. However, in the TiN TE sample, an obvious Ta4f shoulder peak was observed at 25.2 eV, which corresponds to Ta 4+ in the deconvoluted binding energy curve . This means that oxygen‐deficient TaO x ( x = 2) was formed in the TiN TE.…”

“…However, in the TiN TE sample, an obvious Ta4f shoulder peak was observed at 25.2 eV, which corresponds to Ta 4þ in the deconvoluted binding energy curve. [29] This means that oxygen-deficient TaO x (x ¼ 2) was formed in the TiN TE. As expected, as shown in Figure 4c, the Ti2p peaks could be deconvoluted into the peaks of various related materials, such as TiN, TiO 2 , and TiO x N y , whereas the Pt4f peak showed an inert chemical characteristic in its binding status.…”