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We have synthesized highly oxygen deficient HfO$_{2-x}$ thin films by controlled oxygen engineering using reactive molecular beam epitaxy. Above a threshold value of oxygen vacancies, p-type conductivity sets in with up to 6 times 10^{21}…
Density functional theory (DFT) and DFT corrected for on-site Coulomb interactions (DFT+U) calculations are presented on Aluminium doping in bulk TiO$_2$ and the anatase (101) surface. Particular attention is paid to the mobility of oxygen…
BiVO$_4$ is a promising photocatalyst for efficient water oxidation, with surface reactivity determined by the structure of active catalytic sites. Surface oxidation in the presence of oxygen vacancies induces electron localization,…
Flexoelectricity is universal in all dielectrics, effective at high temperatures, and a promising transduction technique for nanoelectromechanical systems (NEMS). However, as flexoelectricity is still in its early stages, many aspects…
We investigated the unoccupied part of the electronic structure of the oxygen-deficient hafnium oxide (HfO$_{\sim1.8}$) using soft x-ray absorption spectroscopy at O $K$ and Hf $N_3$ edges. Band-tail states beneath the unoccupied Hf 5$d$…
Ferroelectricity in the complementary metal-oxide semiconductor (CMOS)-compatible hafnia (HfO$_2$) is crucial for the fabrication of high-integration nonvolatile memory devices. However, the capture of ferroelectricity in HfO$_2$ requires…
The structures, optical and electrical transport properties of SnO$_2$ films, fabricated by rf sputtering method at different oxygen partial pressures, were systematically investigated. It has been found that preferred growth orientation of…
HfO2, a simple binary oxide, holds ultra-scalable ferroelectricity integrable into silicon technology. Polar orthorhombic (Pbc21) form in ultra-thin-films ascribes as the plausible root-cause of the astonishing ferroelectricity, which has…
The poor structural stability of phosphorene in air was commonly ascribed to humidity and oxygen molecules. Recent exfoliation of phosphorene in deoxygenated water promotes the need to re-examine the role of H2O and O2 molecules.…
A comprehensive analysis is presented for the diffusivity of oxygen defects and oxygen self-diffusion in ThO$-2$. The migration energy and diffusivity of oxygen defects with nominal charges have been investigated using density functional…
Transition metal carbides/nitrides (MXenes) are a newly developing class of two-dimensional (2D) materials with technically robust properties that can be finely tuned by planar surface functionalization. Herein, the critical role of oxygen…
Systematic investigation of atomic structure of N-ion implanted TiO2 (thin films and bulk ceramics) was performed by XPS measurements (core levels and valence bands) and first-principles density functional theory (DFT) calculations. In bulk…
Memristive devices have gained significant attention for their potential in next-generation non-volatile memory and neuromorphic computing architectures. Among emerging candidates, transition metal oxides have proven particularly promising.…
In view of the recent experimental reports of unexpected ferromagnetism in HfO$_{2}$ thin films, we carried out first principles investigations looking for magnetic order possibly brought about by the presence of small concentrations of…
Migration of oxygen vacancies has been proposed to play an important role in the bipolar memristive behaviors since oxygen vacancies can directly determine the local conductivity in many systems. However, a recent theoretical work…
Crystalline structures, zone-center phonon modes, and the related dielectric response of the three low-pressure phases of HfO2 have been investigated in density-functional theory using ultrasoft pseudopotentials and a plane-wave basis. The…
Atomic-scale understanding of HfO2 ferroelectricity is important to help address many challenges in developing reliable and high-performance ferroelectric HfO2 (fe-HfO2) based devices. Though investigated from different angles, a factor…
HfO2-based ferroelectric materials are promising for the next generation of memory devices, attracting significant attention. However, their potential applications are significantly limited by fatigue and imprint phenomena, which affect…
Structural softness - often characterized by unstable phonon modes and large electromechanical responses - is a hallmark of ferroelectric perovskites like BaTiO3 or Pb(Ti,Zr)O3. Whether HfO2 ferroelectrics present any such structural…
Oxygen vacancies in two-dimensional metal-oxide structures garner much attention due to unique conductive, magnetic and even superconductive functionalities they induce. Ferroelectric domain walls have been a prominent recent example…