Synergistic Effect of Singly Charged Oxygen Vacancies and Ligand Field for Regulating Transport Properties of Resistive Switching Memories

Abstract

The controlled incorporation of defect species in amorphous oxide (AO) for regulating charge transport properties is highly demanding and challenging, especially for resistive switching (RS) memories. Here, we use pulsed electron beam deposition technique to engineer the growth of AO films, which show a large decrease (∼33%) in the t2g–eg gap. Our collective experiments and density functional theory (DFT) based ab initio simulations reveal the presence of undercoordinated TiO5 units, causing a decrease in the t2g–eg gap. Further, the importance of TiO5 in facilitating excess electron localization is demonstrated, showing an evolution of a broad defect band within the energy gap. The origin of this band (singly charged oxygen vacancy) is resolutely established by X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements and is also supported by calculated partial charge density and Bader charge analysis. The preeminence of singly charged oxygen vacancies cause a low-current level (up to 1–5 nA) RS operation with a gradual change of resistance states, which could set their path for the energy-efficient neuromorphic computing application. Finally, a new model based on probabilistic Markov chain algorithm is also developed to unfold the gradual change of resistance states from the fundamental defect interaction perspective.

Opening up a Radical Cross-Coupling Etherification Path by a Defect-Rich Cu/ZrO2 Catalyst for a High-Value Transformation of HMF

“…50-1089). − The defect structures of all catalysts were characterized by ESR and XPS. The results show that (Figure A) the signals attributed to the unpaired metal electron vacancies (zirconium vacancies in this case) and unpaired electron oxygen vacancies appear at g = 2.047 and g = 2.003, respectively, in all catalysts. − The defect density was quantitatively analyzed by testing the electron spin number, and the results are shown in Table . What needs explanation is that the electron spin number, also called the electron spin quantum number, refers to a quantum number describing the spin motion of an electron, which is usually a quantitative description of the density of the substances with unpaired electrons (or single electrons) in their molecular orbitals, such as the density of the defect.…”

Toward a Comprehensive Understanding of Amorphous Photocatalysts: Fundamental Hypotheses and Applications in CO2 Photoreduction

“…Only because of the additional electron trapped in the vacancy sites and consequently persisting in the localised electronic energy states as mid‐gap energy are the singly charged oxygen vacancies active for photocatalytic activity. There is a large amount of the localised state and potential characteristics derived from the oxygen vacancies in the case of amorphous materials [62] …”

“…There is a large amount of the localised state and potential characteristics derived from the oxygen vacancies in the case of amorphous materials. [62]…”

Direct Oxidation of Cyclohexane to Adipic Acid by a WFeCoO(OH) Catalyst: Role of Brønsted Acidity and Oxygen Vacancies

“…25,34,38 Oxygen vacancies can be neutral (V o 0 ), singly charged (V o +1 ), or doubly charged (V o +2 ) depending upon the number of electrons trapped. 54 Due to the paramagnetic nature, the neutral (V o 0 ) and singly charged oxygen vacancies (V o +1 ) with S = 1 and S = 1/2, respectively, are electron spin resonance (ESR) active. 54,55 However, our analysis of WFeCoO(OH) using ESR spectroscopy at 298 and 77 K (Figure S8 and S9, respectively, Supporting Information) showed no signature peaks, suggesting absence of these two types of oxygen vacancies.…”

“…54 Due to the paramagnetic nature, the neutral (V o 0 ) and singly charged oxygen vacancies (V o +1 ) with S = 1 and S = 1/2, respectively, are electron spin resonance (ESR) active. 54,55 However, our analysis of WFeCoO(OH) using ESR spectroscopy at 298 and 77 K (Figure S8 and S9, respectively, Supporting Information) showed no signature peaks, suggesting absence of these two types of oxygen vacancies. To further validate these observations, energetics for the creation of a surface oxygen vacancy were calculated using the DFT method at the catalyst surfaces of CoO(OH), WCoO(OH), FeCoO(OH), and WFeCoO(OH).…”