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Effect of high temperature-high pressure treatment on strain state of the lattice mismatched InAs layers grown on the GaAs substrate was investigated by means of X-ray diffraction methods. The InAs layers were grown on (100) oriented GaAs by molecular beam epitaxy. Measurements of the rocking curve width and lattice parameters were carried out using high resolution diffractometer. Annealing of the InAs/GaAs structure performed at high pressure changes its strain state and defect structure. Especially, annealing at the growth temperature at high pressure was found to be effective in improvement of the structural perfection of the layer. It means that thin InAs layers having comparatively low dislocation density can be produced by high temperature - high pressure procedure. The relative changes of threading dislocation density were sensitive to the temperature of the treatment, however they were independent of the primary defect structure of the samples.

We have fabricated perovskite superlattices consisting of ferromagnetic metallic oxide Nd0.67Sr0.33MnO3 (NSMO) and superconducting YBa2Cu3O7 (YBCO). We have investigated structural, transport and magnetic properties of a series of multilayers, in which the layer thickness of NSMO is fixed and that of YBCO varied from 2 to 6 unit cells. We find that the superconducting phase is suppressed for YBCO layer thickness lower than 3 unit cells in NSMO/YBCO multilayered structure. Magnetic moment versus external magnetic field hysteresis curves shows a coexistence of ferromagnetism and superconductivity nearly in the scale of their characteristic lengths.

Superlattices with magnetic layers containing from 8 to 16 GaMnAs monolayers corresponding to the mixed crystal composition between 5 and 6% of Mn and from 4 to 10 GaAs monolayers were grown by the low temperature MBE technique and characterized by Raman scattering. Folded acoustic phonons were observed for all superlattices in the Raman scattering spectra. The interlayer exchange coupling, found previously by the wide-angle neutron diffraction in selected superlattices was investigated by the spin-polarized neutron reflectometry. It was always of ferromagnetic type, no trace of antiferromagnetic coupling was found.

The antiferromagnetic (AFM) interlayer exchange coupling for sputtered Fe/Si multilayers have been studied by magnetometry, wide-angle neutron diffraction, and spin-polarized neutron reflectometry. Ferromagnetic resonance and Raman scattering measurements have been applied for the characterization of the multilayers. To look for a possible modification of exchange coupling when Si is replaced by Ge, similar Fe/Ge multilayers have been prepared by the same technique. No AFM coupling has been found for Fe/Ge system. Present results differ in part from the literature data and suggest an influence of the sample preparation on the details of its magnetic properties.

Spin-wave excitations (magnons) of AF-III zinc-blende MnTe were modeled with a Heisenberg Hamiltonian, including isotropic exchanges and magnetic anisotropy, and compared to experimental results determined previously. The calculated dispersions depend on the assumption made on the spin arrangement of the structure, which leads to exclude the Keffer-canted structure. From the fit of theoretical curves to experimental data the dominant exchange constants were determined, pointing out the importance of distant neighbors. The effects of the anisotropy and of the tetragonal structural distortion on the spin-wave spectrum allowed a discussion on their contribution and evidenced the need for a more specific anisotropic-exchange term. The value of the nearest-neighbor exchange interaction in pure MnTe determined by this way was compared with the interpolation of data taken for diluted magnetic systems.

The zinc blende (metastable) modification of mercury sulphide was stabilized by the partial substitution of Hg atoms by Mn, Fe, and Co. The structure of such crystals grown by the modified Bridgman method was investigated by X-ray diffraction and electron transmission spectroscopy techniques. The single-phase character of the crystals was demonstrated, the presence of defects resulting from the disorder in the stacking sequence of (111) layers was evidenced.

The effect of high hydrostatic pressure ‐ high temperature treatment on strain state of thin GaAs layers, grown on vicinal (001) Si substrate, misoriented towards [110] with different miscut angles and with two different orientations of GaAs layer in relation to the miscut direction, was investigated by X‐ray diffraction methods. The strain of the GaAs layers and GaAs/Si samples bending decreases when subjected to the treatment at T = 670 K under enhanced hydrostatic pressure (1.2 GPa). Dependence between the stress‐induced structural changes and the orientation of GaAs miscut angle as well as peculiarities of the temperature‐pressure treatment were determied. It has been shown that the amount of relaxed strain depends on the initial defect structure of the GaAs/Si hetrostructure. After re‐annealing the samples at higher temperature (870 K ‐ 1.2 GPa), the strain and sample bending were the same as that after the treatment at 670 K ‐ 1.2 GPa but the defect structure of layers was improved.

Field-cooled, zero-field-cooled and remanent magnetization of Cd1—xMnxTe, Zn1—xMnxTe (0.5 < x ≤ 1.0) epilayers, including the end-point MnTe, were measured as functions of temperature and magnetic field. For all diluted systems (x< 1.0) a spin-glass-like behavior was observed. Irreversible effects, typical for the spin-glass, tend to decrease in magnitude with an increasing Mn concentration and vanish in MnTe. This spin-glass–antiferromagnet transition is gradual. Magnetic phase diagrams of Cd1—xMnxTe and Zn1—xMnxTe are discussed.

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The structure of AlGaAs, MnMgTe/CdTe and CdTe epitaxial layers deposited on GaAs substrates was studied by high-resolution X-ray diffractometry. The reciprocal lattice mapping and the rocking curve techniques were used for the samples aligned with either [110] or [1-10] direction perpendicular to the diffraction plane. Our results show that strains in the investigated samples were anisotropic. This means that unit cells of layers were not tetragonal but possessed a lower symmetry. Our findings can be explained by anisotropic relaxation of strain caused by a higher mobility of the [1‐10]-oriented dislocations than that oriented in the [110] direction.

The lattice dynamics of cubic mercury chalcogenides (HgTe, HgSe, β-HgS) was investigated by IR reflectivity, Raman scattering and inelastic neutron scattering measurements. The important role of two-phonon Raman scattering related to TA excitations was confirmed for HgSe and β-HgS and explained by the particular TA dispersion for mercury compounds. Analysis of the optical spectra taken for HgSe demonstrates that the resonant two-phonon difference process (widely accepted for HgTe, HgSe and the mixed crystals grown on the basis of these compounds) is not able to explain the present experimental data.

ZnYbTe and CdYbTe thin films were grown by molecular beam epitaxy (MBE) on ZnTe and CdTe buffer layers crystallized on GaAs(100) substrates. At the chosen growth temperature (320°C for CdYbTe and 340°C for ZnYbTe) the maximum concentration of ytterbium was found to be 5% in CdTe and 3% in ZnTe. The layers were characterized by X-ray diffraction, photoluminescence (PL) and reflectivity measurements. X-ray investigations have shown that there was a small admixture of pure YbTe in the samples. From the optical measurements it follows that in CdYbTe and ZnYbTe, Yb can be found both in 2+(as in YbTe) and 3+(as in Yb doped II–VI compounds) valence state. The relatively broad PL spectra detected at the energies close to the Yb3+4f13(2F52→ 2F72)transitions indicate that at such a high concentration Yb incorporates with certain inhomogeneity into the crystal lattices of ZnTe and CdTe.

Lattice dynamics of HgSe and β-HgS was studied by three independent methods: IR reflectivity, Raman scattering and neutron scattering measurements. New interesting features, found in the spectra are explained and analyzed in detail. In particular, the possible influence of the isotope effects on the results of measurements mentioned above is discussed.

Molecular-beam epitaxy was successfully used to grow new diluted magnetic semiconductor Mg 1− x Mn x Te with zinc blende structure. Layers 3-5 μm thick with Mg molar fraction ranging between 0 and 1 were grown on GaAs(1 0 0) 2° off substrates from elemental sources. Layers with Mg content greater than 0.8 were not stable in air and decomposed with time. To avoid this, MgTe films were protected against hydration by CdTe cap layer. Under such protection they proved to be stable for several weeks. X-ray diffraction measurements did not reveal any other crystallographic phases apart from cubic zinc blende phase and indicated a good crystallographic quality. Lattice parameters were determined by high-resolution X-ray diffraction for the entire range of compositions. The energy gap variation with Mg molar fraction was studied by magnetic circular dichroism in reflectance configuration at T = 2 K. Measurements of magnetic properties performed by SQUID magnetometry evidenced formation of a spin-glass-like phase. The magnetic phase diagram T c ( x ) is presented.

An experimental and theoretical analysis of spin-wave excitations (magnons) in ultra-thin films of a magnetic semiconductor has been performed. Cubic MnTe, which possesses a frustrated long-range antiferromagnetic order when deposited in thick layers, was the material selected for such studies. In the low-frequency part of the Raman spectra, a complex structure has been observed in crossed polarization − z ( x , y ) z at low temperature on (MnTe) k /(CdTe) m multilayers (where m ≥ 8). This structure can be attributed to magnons in thin MnTe slabs.

Excitons in Cd 1− x Mn x Te and Cd 1− x −y Mg y Mn y Te parabolic and half-parabolic quantum wells are investigated by magnetooptical methods. The diagonal and nondiagonal (in the harmonic oscillator quantum numbers) transitions are observed. Apart from 1s excitons we observed also 2s and 3s states in the presence of a magnetic field. The results are discussed in terms of a simple variational calculation of the exciton energy. It is shown that a parabolic confining potential very effectively reduces the dimensionality of the excitons leading to large values of their binding energy even in relatively wide quantum wells. The truly parabolic shape of the confining potential in the investigated structures is proved by an analysis of spin splitting of the exciton states.

Abstract: The effect of absorbed hydrogen on the145Nd NMR in Nd15Fe77B8 has been investigated at helium temperatures. Hydrogen absorption is accompanied by a drop of NMR frequencies and changes in the quadrupole splitting. The drop of NMR frequencies is related to the lattice expansion. The influence of the hydrogen on the spin reorientation can be responsible for the changes in the quadrupole splitting.

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Microstructural transformations in p-GaAs/Ni/Zn contact have been studied by a combined use of XTEM, SIMS and XRD. The results give evidence that the thermally activated contact reaction leads to the formation of an ohmic contact to p-GaAs via the process of solid-phase regrowth.

Monocrystalline films of sphalerite-type (Cd,Zn)S were grown on GaAs by atomic layer epitaxy in a gas flow system. Structural properties were determined and compositional uniformity confirmed by means of X-ray diffraction and photoluminescence.