scholarly journals Asymmetric Interfaces in Epitaxial Off-Stoichiometric Fe3+xSi1−x/Ge/Fe3+xSi1−x Hybrid Structures: Effect on Magnetic and Electric Transport Properties

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 131
Author(s):  
Anton S. Tarasov ◽  
Ivan A. Tarasov ◽  
Ivan A. Yakovlev ◽  
Mikhail V. Rautskii ◽  
Ilya A. Bondarev ◽  
...  

Three-layer iron-rich Fe3+xSi1−x/Ge/Fe3+xSi1−x (0.2 < x < 0.64) heterostructures on a Si(111) surface with Ge thicknesses of 4 nm and 7 nm were grown by molecular beam epitaxy. Systematic studies of the structural and morphological properties of the synthesized samples have shown that an increase in the Ge thickness causes a prolonged atomic diffusion through the interfaces, which significantly increases the lattice misfits in the Ge/Fe3+xSi1−x heterosystem due to the incorporation of Ge atoms into the Fe3+xSi1−x bottom layer. The resultant lowering of the total free energy caused by the development of the surface roughness results in a transition from an epitaxial to a polycrystalline growth of the upper Fe3+xSi1−x. The average lattice distortion and residual stress of the upper Fe3+xSi1−x were determined by electron diffraction and theoretical calculations to be equivalent to 0.2 GPa for the upper epitaxial layer with a volume misfit of −0.63% compared with a undistorted counterpart. The volume misfit follows the resultant interatomic misfit of |0.42|% with the bottom Ge layer, independently determined by atomic force microscopy. The variation in structural order and morphology significantly changes the magnetic properties of the upper Fe3+xSi1−x layer and leads to a subtle effect on the transport properties of the Ge layer. Both hysteresis loops and FMR spectra differ for the structures with 4 nm and 7 nm Ge layers. The FMR spectra exhibit two distinct absorption lines corresponding to two layers of ferromagnetic Fe3+xSi1−x films. At the same time, a third FMR line appears in the sample with the thicker Ge. The angular dependences of the resonance field of the FMR spectra measured in the plane of the film have a pronounced easy-axis type anisotropy, as well as an anisotropy corresponding to the cubic crystal symmetry of Fe3+xSi1−x, which implies the epitaxial orientation relationship of Fe3+xSi1−x (111)[0−11] || Ge(111)[1−10] || Fe3+xSi1−x (111)[0−11] || Si(111)[1−10]. Calculated from ferromagnetic resonance (FMR) data saturation magnetization exceeds 1000 kA/m. The temperature dependence of the electrical resistivity of a Ge layer with thicknesses of 4 nm and 7 nm is of semiconducting type, which is, however, determined by different transport mechanisms.

2017 ◽  
Vol 31 (05) ◽  
pp. 1750032
Author(s):  
Jing Zhang ◽  
San Huang Ke ◽  
Derwyn A. Rowlands

Using first-principles calculation method, we have investigated the zone-center phonon modes, dielectric and transport properties of the LiNbO3-type CdPbO3. The results show that the relatively large peaks of infrared (IR) and Raman spectra mainly come from the [Formula: see text] and [Formula: see text] modes, respectively. The dielectric constant calculations reveal that this compound is positive uniaxial crystal and has the large dielectric constants. By investigating the electric transport properties using gold as electrode, the interesting negative differential resistance (NDR) effect can be observed, which reveals this compound should have important application in semiconducting electronic devices.


ChemInform ◽  
2008 ◽  
Vol 39 (6) ◽  
Author(s):  
Sheng-qing Xia ◽  
Jonathan Hullmann ◽  
Svilen Bobev ◽  
Arif Ozbay ◽  
Edmund R. Nowak ◽  
...  

2000 ◽  
Author(s):  
Phillip Gibson ◽  
Heidi Schreuder-Gibson

Abstract Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10 to 500 nanometers in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers which are useful for chemical protective clothing. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed. Performance measurements on experimental electrospun fiber mats compared favorably with transport properties of textiles and membranes currently used in protective clothing systems. It was found that electrospun layers presented minimal impedance to moisture vapor diffusion required for evaporative cooling. There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure were also evident in environmental scanning electron microscope images of the pore/fiber rearrangement as the membrane was stretched. Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlated with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam. Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications which exhibits high breathability, elasticity, and filtration efficiency.


CrystEngComm ◽  
2019 ◽  
Vol 21 (21) ◽  
pp. 3330-3342 ◽  
Author(s):  
Matylda N. Guzik ◽  
Matthias Schrade ◽  
Raluca Tofan ◽  
Patricia A. Carvalho ◽  
Kristian Berland ◽  
...  

Experimental study reveals the apparent ordered arrangement of excess Ni at the nominally vacant sublattice in thermoelectric Ti1−xHfxNi1.0/1.1Sn half-Heusler compounds.


2013 ◽  
Vol 724-725 ◽  
pp. 1029-1032 ◽  
Author(s):  
Qing Lin He ◽  
Feng Gao ◽  
Hong Zhang Song ◽  
Xing Hu

The electric resistivity, Seebeck coefficients and power factors of Y1-xEuxBaCo4O7+δ(x = 0.0, 0.05, 0.1, 0.2) ceramics were investigated from 400K to 1000K. The results show that the presence of Eu decreases electrical resistivity, and has little effect on Seebeck coefficients of the samples. The activation energy of conductivity is calculated by the Arrhenius plots in the semiconductive region. According to power factors, the optimum Eu substitution amount is x = 0.1, which results in a higher power factor of 67.5 μWm-1K-2at 1000K, 30% higher than unmodified sample YBaCo4O7+δ.


2007 ◽  
Vol 69 (5) ◽  
pp. 571-578 ◽  
Author(s):  
L. E. Ermakova ◽  
M. P. Sidorova ◽  
N. A. Zhura

2008 ◽  
Vol 104 (12) ◽  
pp. 123904 ◽  
Author(s):  
S. L. Huang ◽  
L. X. Guan ◽  
J. B. Yi ◽  
B. C. Zhao ◽  
Y. Wu ◽  
...  

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