The present paper pertains to mechanical properties and structure of nanocrystalline multiferroic BeFiO3(BFO) thin films, grown by atomic layer deposition (ALD) on the Si/SiO2/Pt substrate. The usage of sharp-tip-nanoindentation and multiple techniques of structure examination, namely, grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectrometry, enabled us to detect changes in elastic properties(95 GPa≤E≤118 GPa)and hardness(4.50 GPa≤H≤7.96 GPa)of BFO after stages of annealing and observe their relation to the material’s structural evolution. Our experiments point towards an increase in structural homogeneity of the samples annealed for a longer time. To our best knowledge, the present report constitutes the first disclosure of nanoindentation mechanical characteristics of ALD-fabricated BeFiO3, providing a new insight into the phenomena that accompany structure formation and development of nanocrystalline multiferroics. We believe that our systematic characterization of the BFO layers carried out at consecutive stages of their deposition provides pertinent information which is needed to control and optimize its ALD fabrication.
This paper pertains to elastic properties of InAs and GaAs semiconducting crystals containing various amounts of vacancies--the relevant issue in the case of nanostructured electronic materials. The linear relationship between elastic constants and point defects concentration deduced from our classical molecular dynamic and ab initio calculations, confirms that an increasing vacancy content results in a decrease of pertinent elastic parameters, namely the crystal elastic stiffness-tensor components, the effect called herein "the softening of material" for simplicity. The pseudo-potential-based approach provides us results compatible with the available experimental data, while the alternatively used empirical potentials failed to account for different kind of vacancies on the elastic properties of semiconductors. Our results provide an expanded insight into the problems of modeling of the properties of the defected InAs and GaAs crystal structures. This issue is of interest to nanoelectronics and production of nanomaterials currently.
The band structure investigations for Sm(Ni1¡xCoxq3 alloys by means of X-ray photoelectron spectroscopy (XPS) and an ab initio density functional theory (DFT) calculations are presented. The aim was to determine an effect of Ni/Co substitution on the electronic structure of the alloys. Investigations have shown that the Ni/Co substitution results in a reconstruction of the valence band (VB), especially the intensity near the Fermi level decreases with Co content. An ab initio simulated XPS VB spectra agree qualitatively with experimental ones with the exception of the Sm-4f sub-spectra where the multiplet decomposition is observed. Calculations shown that variation of magnetization in Sm(Ni1¡xCoxq3 is driven mainly by the Ni/Co-3d and Sm-5d states polarization and increases linearly with rising Co content.
The present paper concerns the elastic-plastic nanodeformation of Te-doped GaSb crystals grown by molecular beam epitaxy on the n-type of GaSb substrate. The conventional analysis of nanoindentation data obtained with sharp triangular (Berkovich) and spherical tip revealed the elastic modulus (E = 83.07 ± 1.78 GPa), hardness (H = 5.19 ± 0.25 GPa) and "true hardness" (HT = 5.73 ± 0.04 GPa). The registered pop-in event which indicates the elastic-plastic transition in GaSb crystal points towards the corresponding yield strength (σY = 3.8 ± 0.1 GPa). The origin of incipient plasticity in GaSb crystal is discussed in terms of elastic-plastic deformation energy concept.
Effect of silicon doping on the elastic-plastic transition of GaAs crystal is demonstrated by results of nanoindentations and ab initio simulations. The performed experiments show that an increase of silicon concentration causes a decrease of the contact pressure at the onset of permanent nanodeformation of GaAs crystal. Ab initio calculations demonstrate that presence of Si atoms in the crystal lattice suppresses the shear modulus as well as the pressure of equilibrium between zinc-blende and rock-salt phases of GaAs. Furthermore, it is argued that the effect of dislocations pinning to Si dopants is essential for clarification of GaAs yielding.
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