Nanodomain structure of single crystalline nickel oxide

Abstract

In this work we present a comprehensive study of the domain structure of a nickel oxide single crystal grown by floating zone melting and suggest a correlation between point defects and the observed domain structure. The properties and structure of domains dictate the dynamics of resistive switching, water splitting and gas sensing, to name but a few. Investigating the correlation between point defects and domain structure can provide a deeper understanding of their formation and structure, which potentially allows one to tailor domain structure and the dynamics of the aforementioned applications. A range of inhomogeneities are observed by diffraction and microscopy techniques. X-ray and low-energy electron diffraction reveal domains on the submicron- and nanometer-scales, respectively. In turn, these domains are visualised by atomic force and scanning tunneling microscopy (STM), respectively. A comprehensive transmission electron microscopy (TEM) study reveals inhomogeneities ranging from domains of varying size, misorientation of domains, variation of the lattice constant and bending of lattice planes. X-ray photoelectron spectroscopy and electron energy-loss spectroscopy indicate the crystal is Ni deficient. Density functional theory calculations—considering the spatial and electronic disturbance induced by the favourable nickel vacancy—reveal a nanoscale distortion comparable to STM and TEM observations. The different inhomogeneities are understood in terms of the structural relaxation induced by ordering of nickel vacancies, which is predicted to be favourable.

On the properties of NiO powders obtained by different wet chemical methods and calcination

“…These values are higher than those reported in the literature, both experimentally, 4.1684 Å, as well as predicted by density functional theory calculations, 4.17 Å. [30][31][32] In Figure 4B, the following trends can be observed: (i) For the sample obtained by hydrothermal synthesis, the lattice parameter increased after the recalcination in the O 2 -rich atmosphere, contrasting with the sol-gel and coprecipitation powders, whose lattice parameter decreased; (ii) The values for hydrothermal synthesis were higher than those obtained by the two other methods; (iii) For the sol-gel route, the lattice parameter changed very slightly after the different calcination process, while it was considerably modified for the sample obtained by coprecipitation. The lattice parameter of oxides is influenced by several factors, mainly by the size and charge of the constituent ions, impurities, and internal strain.…”

“…In Figure 3B, the obtained lattice parameters are presented and as can be seen, they were influenced by both the synthesis route and the calcination atmosphere, ranging between 4.1782 and 4.1788 Å. These values are higher than those reported in the literature, both experimentally, 4.1684 Å, as well as predicted by density functional theory calculations, 4.17 Å 30–32 …”

Strong interfacial Dzyaloshinskii–Moriya induced in Co due to contact with NiO

“…However, only a few works so far have paid attention on how the AFO influences the iDMI in ferromagnets. Therefore we will focus on NiO, which strongly pins ferromagnetic spins by exchange bias coupling 8 and in stoichiometric form is an insulator (note that even single-crystal NiO may deviate from the proper stoichiometry Ni:O ratio (1:1) because of lattice defects (vacancies/interstitials) 9 , 10 ).…”

Microstructural Insights into Performance Loss of High‐Voltage Spinel Cathodes for Lithium‐ion Batteries

“…Based on the spatial distribution of the different phases, the phase transformation most probably follows a sequence from spinel LNMO to the Mn 3 O 4 -like structure, and then to the rock-salt structure. Considering that both NiO and MnO possess a cubic rock-salt structure, [44,45] oxygen loss from the newly exposed surfaces during cycling could facilitate the phase transformation.…”