Cathodoluminescence of ZnS single crystals subjected to thermal annealing in vapors of the constituents

The 77°K cathodoluminescence spectra of ZnS single crystals grown from the melt and annealed in vapors of the constituents were studied in the spectral region 360 to 550 nm. The single crystals contained oxygen whose phase state could be changed by thermal annealing. The effect of oxygen in the ZnS lattice on the appearance and intensities of various bands in the zinc sulfide spectrum was investigated. It turned out that the bands at 390–400 nm, 410–430 nm, and 500–525 nm are associated with the luminescence of a solid solution of ZnS· O in the lattice. The intensity of the green luminescence was a function of oxygen concentration in precipitates of the solid solution on dislocations. The luminescence in the 363 to 370 nm region is associated with zinc oxide which separates from ZnS containing various amounts of sulfur.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 84–88, May, 1975.     

Low-voltage cathodoluminescence of ZnS single crystals

Bright blue and green cathodoluminescence from low resistivity ZnS crystals has been observed under the excitation of low-energy electron beams of several tens of volts; i.e., 40 fL at 50 V. Properties of the surface of the crystals are studied by the dependence of current and brightness on applied voltage and by the spectra of cathodoluminescence and photoluminescence.     

Frequency dependence of electroluminescence processes in ZnS crystals

The frequency dependence of the integral electroluminescence brightness and the electrical conductivity of ZnS-Cu, Cl and ZnS-Mn single crystals was examined. It was established that the correlation between the integral electroluminescence brightness and the electrical conductivity in ZuS-Cu, Cl crystals improves slightly at high frequencies of the exciting field, whereas no such correlation exists for the frequency range 30 Hz-18 Hz in ZnS-Mn crystals. Conclusions regarding the various excitation mechanisms of the electroluminescence in ZnS-Cu, Cl and ZnS-Mn crystals are drawn.In conclusion, the authors express their sincere gratitude to P. E. Ramazanov for his valuable advice.     

X-ray crystallographic investigation of ZnS:Ag, Cu, Mg single crystals

Splitting of the profiles of diffraction lines from the [110] planes of ZnS:Ag, Cu, Mg single crystals into two, and sometimes three, peaks has been observed. The relative intensity of the peaks is compared with the volume fraction, obtained from optical excitonic spectra, of interlayers of a hexagonal phase in the samples. Fiz. Tverd. Tela (St. Petersburg) 39, 49–51 (January 1997)     

Quenching of photoluminescence in ZnS:Cu single crystals

Experiments on the quenching of photoluminescence in ZnS:Cu single crystals by secondary radiation are reported. Quenching of emission at photon energies of 1.4, 1.7, 2.4 and 2.75 eV by photons at 0.93, 1.6, 2.0, 2.4 eV is found, with a possible fifth peak at 2.7 eV. The effect of each secondary band on each emission band is found to be equivalent. This is explained in terms of a model in which all quenching transitions effectively fill a common ground state for the green/blue emission.     

Brightness waves of different activators in ZnS single crystals

The brightness waves of ZnS single crystals with copper and manganese activators have been examined. The measurements were made on single emitting spots of the crystals with time resolution. It could be ascertained that the single spots act independently and that the copper and manganese centres show different electroluminescent properties. The observed phenomena have been investigated in connection with recent electroluminescence theories.     

Electron paramagnetic resonance (EPR) and spin-lattice relaxation of trigonal Co2+ centers in ZnS single crystals

Single crystals with a ZnS structure are of great practical value, in which connection they are studied in detail by different methods including the spectroscopic. In particular, such crystals activated by ion impurities are investigated in detail by the EPR method. However, the spin-lattice relaxation (SLR) of such systems has hardly been studied. Papers studying the SLR of cubic Mn²⁺ centers [1] and trigonal Nd³⁺ and Yb³⁺ [2] centers in ZnS did only appear recently.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 141–143, August, 1978.The authors are grateful to A. I. Ryskin for providing the single crystals for the investigation and to R. Yu. Abdulsabirov for assistance in performing the experiments.     

EPR investigation of local paramagnetic centers in perovskite-like crystals

In ScF₃ single crystals (pure and doped) as well as in Rb₂KScF₆ and Rb₂KDyF₆ crystals with a perovskite-like structure, point nanodefects (vacancy in place of trivalent cations) have been found and studied. Electron paramagnetic resonance has been used to investigate local paramagnetic centers that are not detected using X-ray diffraction. The angular dependence of the spectra indicates a local distortion of the cubic symmetry of the crystals. An additional hyperfine structure in the observed spectra is due to the delocalization of electrons over six F^? ions forming the first coordination polyhedron around the vacancy. The crystals studied are characterized by a high electron mobility and a high electron velocity, which depends on the impurity. The high mobility of electrons of the cation center can be indirectly responsible for the structural phase transition occurring in the ScF₃ crystal under uniaxial pressure.     

EPR studies of rhodium in LiH and LiD single crystals

EPR studies of rhodium in LiD and LiH single crystals reveal an axial rhodium complex with the unpaired electron in a 4d_x²?y² molecular orbital and with 5% of the spin density transferred to the planar ligands.     

Pulsed electron beam annealing and furnace annealing of Cu-implanted Al single crystals

A comparison has been performed of the effects of pulsed electron beam annealing (PEBA) and furnace annealing on the distribution and lattice site occupation of Cu implanted into Al single crystals. Both parameters have been determined by Rutherford backscattering and channeling measurements with 2 MeV He⁺ ions. With furnace annealing at 300°C the Cu diffusion into the bulk was determined by the release process from the implanted layer, while for PEBA a redistribution of the copper was observed for pulses with deposited energy densities above the threshold for melting. A supersaturated solid solution with 95% (2.1 at.%) of the impurity atoms on substitutional sites was formed by the electron beam treatment. After thermal annealing only little improvement of the lattice site occupation was observed with 66% of the impurities atoms on lattice sites, however with slight displacements from the perfect positions.     

Polarisation of the IR luminescence of cubic ZnS single crystals

The polarization of the IR luminescence of oriented ZnS crystals has been measured. None of the three main emission bands shows measurable polarization after excitation with polarized or unpolarized light. This result supports centers with symmetryT _d because they do not require any selection rules for the polarization of optical dipole transitions.     

Infra-red enhancement and quenching of photoconductivity in sulfur-annealed ZnS single crystals

Infra-red (IR) enhancement and quenching of photoconductivity has been observed in S-annealed ZnS single crystals. These effects are studied as a function of the wavelength and the intensity of both types of radiation. Some interesting new properties are found, e.g. the decrease of a quenching effect at a constant intensity of the ultra-violet (UV) light with an increasing IR-light intensity and the existence of two opposite quenching curves depending on the UV-light intensity. These properties are explained by the appearance, in the investigated crystals, of an ambipolar conductivity state in a certain UV-light intensity range.