The Raman spectra of surface regions of bulk Cu2ZnSnS4 (CZTS) samples with different Cu and Zn cation content were obtained and the differences in the spectra are attributed to statistical disorder effects in the cation sublattice. This disorder in the Cu and Zn sublattices may initiate a change of the crystal symmetry from kesterite‐type $({I\bar 4})$ to $({I\bar 42m})$ space group. The investigated CZTS crystals grown at high temperature are characterised by the co‐existence of regions with different composition ratio of Cu/(Zn + Sn) which results in kesterite and disordered kesterite phases. The presence of a disordered phase with ${I\bar 42m}$ symmetry is reflected in the appearance of a dominant broadened A‐symmetry peak at lower frequency than the peak of the main A‐symmetry kesterite mode at 337 cm–1. We suppose that due to a small energy barrier between these phases the transition from one phase to the other can be stimulated by optical excitation of Cu2ZnSnS4. The analysis of the Raman spectra measured under different excitation conditions has allowed obtaining first (to our knowledge) experimental evidence of the existence of such optically induced structural transition in CZTS. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

ZnO nanorods (NRs) arrays doped with a large concentration of Mn synthesized by aqueous chemical growth and were characterized by SEM, photoluminescence, Raman scattering, magnetic force microscopy (MFM). By comparison of spectra taken on pure and Mn-doped ZnO NRs, a few new Raman impurity-related phonon modes, resulting from the presence of Mn in the investigated samples. We also present a vibrational and magnetic characterization of individual lying nanorods using Raman and MFM imaging. Confocal scanning micro-Raman mapping of the spatial distribution of intensity and frequency of phonon modes in single Mn-doped ZnO NRs nanorods is presented and analyzed for the first time. Mn-related local vibrational modes are also registered in Raman spectra of the single nanorod, confirming the incorporation of Mn into the ZnO host matrix. At higher Mn concentration the structural transformation toward the spinel phase ZnMn2O4 and Mn3O4 is observed mainly in 2D bottom layers. MFM images of Mn-doped ZnO NR arrays and single nanorod were studied in nanoscale at room temperature and demonstrate magnetic behavior. The circular domain magnetic pattern on top of single nanorod originated to superposition of some separate domains inside rod. This demonstrates that long-range ferromagnetic order is present at room temperature. Aligned Mn-doped ZnO NRs demonstrates that long-range ferromagnetic order and may be applied to future spintronic applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-2127-4) contains supplementary material, which is available to authorized users.

In this paper, we investigate the structural properties of AlGaN/GaN heterostructures grown by metal organic chemical vapor deposition on sapphire substrates with different thicknesses using high-resolution x-ray diffraction and Raman scattering methods. We discuss the microscopic nature of spatial-inhomogeneous deformations and dislocation density in the structures. Microdeformations within mosaic blocks and the sizes of regions of coherent diffraction are determined. We reveal a gradient depth distribution of deformations in the mosaic structure of nitride layers, as well as at the interface regions of the sapphire substrate on the microscale level using confocal micro-Raman spectroscopy. We determine that an increase in substrate thickness leads to a reduction in dislocation density in the layers and an increase in the elastic deformations. The features of the block structure of nitrides layers are shown to have a significant influence on their elastic properties.

The effect of both CuO content (1 and 8 mol%) and calcination temperature (T c = 500-1000 • C) on light emitting and structural properties of ZrO 2 -Y 2 O 3 -CuO nanopowders was studied by photoluminescence (PL), X-ray diffraction (XRD) and Raman scattering methods. The samples, calcinated at T c = 500-700 • C, contain the tetragonal ZrO 2 phase predominantly. The increase of T c results in its transformation to monoclinic one, and the phase transformation happens at higher temperature at higher Cu content. It is shown that the increase of T c from 500 to 800 • C results in the Cu incorporation into nanocrystals from the surface entities. This manifests itself in the shift of XRD and Raman peaks of tetragonal phase. The PL spectra demonstrate the presence of two main PL components peaked at about 540 nm and 630 nm in the most samples. The increase of T c from 500 to 1000 • C results in the non-monotonic variation of total PL intensity as well as in minor changes in PL spectra shape. The evolution of PL intensity is explained by both the increase of a crystallinity degree and the variation of the concentration of non-radiative recombination centres. The transformation of PL spectra shape is ascribed to the appearance of radiative Cu Zr centres.

The atomic structure and energy spectrum of Ga(As,P)/GaP heterostructures were studied. It was shown that the deposition of GaAs of the same nominal thickness leads to the formation of pseudomorphic GaAs/GaP quantum wells (QW), fully relaxed GaAs/GaP self-assembled quantum dots (SAQDs), or pseudomorphic GaAsP/GaP SAQDs depending on the growth temperature. We demonstrate that the atomic structure of Ga(As,P)/GaP heterostructures is ruled by the temperature dependence of adatom diffusion rate and GaAs-GaP intermixing. The band alignment of pseudomorphic GaAs/GaP QW and GaAsP/GaP SAQDs is shown to be of type II, in contrast to that of fully relaxed GaAs/GaP SAQDs, which have the band alignment of type I with the lowest electronic states at the indirect L valley of the GaAs conduction band.

We report on the effect of strain on the optical and structural properties of 5-, 10-, and 20-period GaN/AlN superlattices (SLs) deposited by plasma-assisted molecular beam epitaxy. The deformation state in SLs has been studied by high resolution transmission electron microscopy (HRTEM), X-ray diffraction, and micro-Raman, Fourier transform infrared (FTIR), and photoluminescence spectroscopy. HRTEM images showed that the structural quality of the SL layers is significantly improved and the interfaces become very sharp on the atomic level with an increase of the SL periods. A combined analysis through XRD, Raman, and FTIR reflectance spectroscopy found that with increasing number of SL periods, the strain in the GaN quantum wells (QWs) increases and the AlN barrier is relaxed. Based on the dependence of the frequency shift of the E2High and E1TO Raman and IR modes on the deformation in the layers, the values of the biaxial stress coefficients as well as the phonon deformation potentials of these modes in both GaN and AlN were determined. With increasing number of SL periods, the QW emission considerably redshifted in the range lower than the GaN band gap due to the quantum confined Stark effect. The influence of strain obtained by the XRD, Raman, and FTIR spectra on the structural parameters and QW emission of GaN/AlN SLs with different numbers of periods is discussed.

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