Boron doped Si/SiO2/substrate (Si:B) structure with subwavelength grating on the top Si:B layer was studied by spectroscopic ellipsometry and photoluminescence spectroscopy at room temperature. A clear modification of the dielectric function was observed after reactive ion etching of the top Si:B layer subjected to laser lithography to make a subwavelength grating with high precision. A striking feature of the dielectric function of the grated surface layer is a sharp and intense peak at the energy of 2.968 eV in the interband density of states. Emission band with a remarkable peak structure that emerges in the photoluminescence spectrum of the grated multilayer structure at and below the last energy is absent on pure or boron doped Si. The obtained results are discussed in terms of the G-doping effect in the considered surface grated multilayer structure.

Electron paramagnetic resonance studies have been carried out over 3.7‐300 K on micropowders of Ni1‐xZnxFe2O4 ferrites, obtained by high temperature synthesis and preliminary characterized by X‐ray diffraction and differential scanning calorimetry in a wide range of tempera‐tures. Complimentary, scanning probe microscopy, compris‐ing atomic and magnetic force microscopies has been applied to polycrystalline Ni1‐xZnxFe2O4thin films. The correlation between X‐ray and differential scanning calorimetry data has been observed. Deconvolution of the obtained paramagnetic resonance spectra into Gaussian components and their further analysis have allowed retrival of the compensation points of the magnetc momenta of the sublattices of Ni1‐xZnxFe2O4, as well as of superparamagnetism effect and g‐factors dispersion verified by studies on polycrystalline thin films. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

bly because of the obvious difficulties in the preparation of MnBi 2 Te 4 • n(Bi 2 Te 3 ) with high index n and unavailability of samples.We have succeeded in this regard and present here the crystal structure of the members with n = 4, 5, and 6, summarize all available structural data for MnBi 2 Te 4 • n(Bi 2 Te 3 ), trace the evolution of Raman spectra of MnBi 2 Te 4 • n(Bi 2 Te 3 ) that embraces all n from 0 to 6 as well as n = ∞ (Bi 2 Te 3 ), and provide a thorough analysis of the obtained Raman data. II. SYNTHESIS AND CRYSTAL STRUCTUREOF MnBi 2 Te 4 • n(Bi 2 Te 3 )A. Synthesis and crystal growth

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This work is devoted to the experimental study and symmetry analysis of the Raman-active vibration modes in MnBi2Te4·n(Bi2Te3) van der Waals topological insulators, where n is the number of Te–Bi–Te–Bi–Te quintuple layers between two neighboring Te–Bi–Te–Mn–Te–Bi–Te septuple layers. Confocal Raman spectroscopy is applied to study Raman spectra of crystal structures with $$n = 0,1,2,3,4,5,6$$, and ∞. The experimental frequencies of vibration modes of the same symmetry in the structures with different n are compared. The lattice dynamics of free-standing one, three, and four quintuple layers, as well as of bulk Bi2Те3$$(n = \infty )$$ and MnBi2Te4$$(n = 0)$$, is considered theoretically. Vibrational modes of the last two systems have the same symmetry, but different displacement fields. These fields in the case of a Raman-active mode do not contain displacements of manganese atoms for any finite $$n$$. It is shown that two vibrational modes in the low-frequency region of the spectrum (35–70 cm–1) of structures with $$n = 1,\;2,\;3,\;4,\;5$$, and 6 practically correspond to the lattice dynamics of n free quintuple Bi2Те3 layers. For this reason, the remaining two vibration modes, which are observed in the high-frequency region of the spectrum (100–140 cm–1) and are experimentally indistinguishable in the sense of belonging to quintuple or septuple layer or to both layers simultaneously, should also be assigned to vibrations in quintuple layers under immobile atoms of septuple layers.