T. P. Surkova

Dynamic Deformations of the Crystal Lattice of Sphalerite in the Zn1−x Co x Se(x=0.01) Compound

Local distortions of the crystal lattice of the semiconductor compound Zn1 − xCoxSe (x = 0.01) have been investigated using thermal neutron diffraction. It has been found that the diffraction patterns of the crystal contain regions of diffuse scattering in the vicinity of strong Bragg peaks at 300 K. As the temperature decreases, the intensity of diffuse scattering effects substantially decreases. Arguments in favor of the assumption that the origin of the diffuse scattering is caused by the Jahn-Teller vibronic effect are presented.

Fine structure of the cubic semiconductor compound Zn0.9Ni0.1S

The fine structure of a single crystal of the Zn0.9Ni0.1S cubic compound synthesized by the chemical transport method has been investigated at room temperature using thermal neutron diffraction. It has been found that the diffraction patterns of this compound, along with strong Bragg reflections of the facecentered cubic phase, include a system of diffuse maxima, which indicate the occurrence of a local deformation of the cubic structure by the Jahn-Teller nickel ions. Results of this experiment have been compared with the previously obtained data for the lightly doped Zn1 − xNixSe single crystal (x = 0.002).

Superstructure of atomic displacements in cubic compounds Zn0.9Ni0.1S and Zn0.7Ni0.3O

The fine structure of cubic compounds Zn0.9Ni0.1S and Zn0.7Ni0.3O has been discussed. At room temperature, their diffraction patterns contain, along with intense Bragg reflections of the face-centered cubic phase, superstructure diffuse maxima demonstrating the ordering of short-wavelength deformations due to Jahn-Teller nickel ions.

Fine structure and magnetism of bulk Zn1 − xCrxSe single-crystal cubic compounds (0 ≤ x ≤ 0.045)

The character of structural and magnetic features of the cubic lattice of bulk Zn1 − xCrxSe crystals (0 ≤ x ≤ 0.045) has been investigated using thermal neutron diffraction and magnetic measurements. It has been found that the diffraction scans of doped crystals contain effects of nuclear diffuse scattering caused by local static atomic displacements in the face-centered cubic (fcc) lattice. Results of magnetic measurements of doped crystals indicate the presence of weak antiferromagnetic correlations, which are a consequence of structural features of these compounds.

Structural features of the system of cubic crystals Zn 0.999 Fe 0.001 S 1 − x Se x ( x = 0, 0.2)

The structural state of cubic single crystals Zn0.999Fe0.001S1 − xSex (x = 0, 0.2) obtained by the chemical transport method has been investigated using thermal neutron diffraction for the first time. It has been found that the diffraction patterns of these crystals contain the previously unknown effects of diffuse scattering caused by local statistic atomic displacements in the metastable fcc lattice.

Exciton luminescence of Cd1−xFexTe solid solutions

Band-edge optical spectra of Cd1−xFexTe solid solutions differ substantially from those of undoped CdTe. The pattern of the change in photoluminescence spectra with increasing Fe concentration is connected with a change in radiative recombination channels.

Transition metal impurities and band offsets in wide gap II-VI semiconductors : Zn1-xMnxSe(Ni) compounds

Zn1−xMnxSe(Ni) solid solutions have been analysed by absorption, reflectivity and resonant photoemission measurements. Valence band offsets for the compounds with different Mn concentrations were estimated from the threshold energy ħωth of the photoionization of Ni2+ ions as well as from photoemission spectra. The contribution of the Mn3d derived states to the valence band was determined.

Fine features of the crystal structure of the semiconductor cubic single crystal Zn0.9V0.1Se

Fine features of the crystal structure of the semiconductor cubic single crystal Zn0.9V0.1Se grown by the chemical transport method have been investigated using thermal neutron diffraction at room temperature. It has been revealed that the neutron diffraction scans of the single crystal, in addition to intense Bragg reflections of the face-centered cubic (fcc) phase, contain a complex system of superstructure reflections. Based on the sphalerite structure, it has been found for the first time that there are clear tendencies toward a decrease in the symmetry and a superposition of short-wavelength and long-wavelength modulations, which are interpreted as a consequence of the perturbations caused by doping vanadium ions and the cooperative response of the matrix lattice to these perturbations. The results of the performed experiment have been compared with the previously obtained data for the Zn0.9Ni0.1S crystal and interpreted as a manifestation of the pre-transition state to a reconstructive phase transition from the cubic phase to the hexagonal phase, which is accompanied by the aforementioned tendencies in the transformation of the structure.

Electronic structure of ZnS:Co and ZnSe:Co crystals

The x-ray photoelectron spectra of the valence bands and inner Co 2p levels of solid solutions of the wide-gap semiconductors ZnS, ZnS:Co, ZnSe, and ZnSe:Co are investigated. The x-ray photoelectron Co 2p spectrum of the ZnS:Co crystal indicates a 3d configuration of the ground state of cobalt and strong covalence of the cobalt-sulfur bond, but somewhat weaker than for CoS. It is established that the edge of the valence band recedes by 0.7±0.1 eV in transition from ZnSe to ZnS.

An inhomogeneously distorted state of the crystal structure of a Zn0.95Fe0.05Se cubic crystal

The structural state of a bulk Zn0.95Fe0.05Se cubic crystal grown by the chemical transport method from the gas phase has been investigated using thermal neutron diffraction at room temperature. It has been found that the measured neutron diffraction patterns of the crystal, in addition to structural Bragg peaks, contain a clearly identified system of superstructure reflections with the wave vector k = (1/3 1/3 1/3)2π/a (where a is the parameter of the cubic unit cell), which is interpreted as a clear evidence of the incipient transition state preceding the concentration phase transformation fcc ↔ hcp. It has been shown that the resulting structural state includes an inhomogeneous microstrain field with the possible appearance of long-wavelength modulations based on the initial sphalerite structure.