Ytterbium Impurity Research Articles

Surface Conductivity of the Ytterbium-Doped Topological Kondo-Insulator SmB6

The temperature dependence of the conductivity of the topological Kondo-insulator (TKI) Sm1 – xYbxB6 is investigated in the temperature range 2 < T < 300 K for compositions with x ≤ 0.024. It is found that the ytterbium impurity most strongly affects the low-temperature (T < 20 K) electrical conductivity: when changing from x = 0 to x = 0.024, the activation energy of bulk conductivity decreases by 1.8 times from 4 to 2.2 meV, and the 2D surface conductivity increases by six times. The separation made for the contributions to the conductivity enables us to establish that the one-parameter scaling model can be used for describing the conductivity of 2D surface states in the Sm1 – xYbxB6 TKI in which both the interaction with phonons and the electron–electron scattering effects are taken into account.

Optical properties of ZnSe(Te) with ytterbium impurity.

We report the results on infrared transmission measurements of non-doped and tellurium-doped crystals of zinc selenide grown from the melt. It was found that non-doped samples feature high transmission (50%-60%) for the wavelengths of 1-22μm. The efficient scintillating crystals of ZnSe(Te) are almost opaque for λ>7 μm. Doping these samples with ytterbium from the gas phase does not achieve any significant transmission increase for non-doped ZnSe samples in the spectral range of 1-22μm. However, it considerably increases (up to 50%) transmission for doped ZnSe(Te) at the wavelengths λ>10 μm. These optical peculiarities were analyzed taking into account restructurization of point defect ensembles created by Te and Yb impurities.

Influence of the ytterbium doping technique on the luminescent properties of ZnSe single crystals

Abstract Luminescent properties of the ytterbium doped zinc selenide crystals with 0.00–8.00 at % concentrations of the Yb impurity within the temperature interval from 6 K to 300 K were studied. Ytterbium doping was performed within three technological processes: during the growth by chemical vapor transport method and by thermal diffusion from the Bi+Yb or Zn+Yb melt. The influence of ytterbium impurity concentration on spectral position and intensity of the various photoluminescent bands in ZnSe emission spectra in visible and infrared range is analyzed. A tendency of ytterbium ions to form associates with background defects was demonstrated. A strong dependence between ytterbium influence on the zinc selenide emission spectra and concentration of selenium vacancies was shown.

Impurity-band induced transport phenomenon and thermoelectric properties in Yb doped PbTe1−xIx

In the present investigation, we report the effect of ytterbium (Yb) impurity band on charge transport and thermoelectric properties in PbTe1-xIx. The temperature dependent interaction of Yb-states with charge carriers and host energy-bands is found to significantly affect the electrical transport parameters in all the investigated samples. Our result indicates that, in the presence of Yb band, the carrier concentration did not increase as effectively as it was found in pristine PbTe with increasing iodine content. An anomalous switching of positive thermopower into negative was found in the samples with lower iodine content. Such phenomena were explained by the redistribution of charge carriers within the different available bands and promotion of vacancy like defects via substitutional impurity. Due to the optimum doping levels, the sample with the highest iodine content showed a decent figure of merit with a peak value of 0.69 at 575 K in the sample with x = 0.007.

A relativistic density functional study of Si n ( n = 7–13) clusters with rare earth ytterbium impurity

Geometries, relative stabilities, HOMO–LUMO gaps, and growth-pattern of YbSi n ( n = 7–13) clusters have been systematically studied. The calculated results show that Yb atom always prefers capping on the surface site of the silicon frame and no cagelike geometries are found up to n = 13, and that the most stable YbSi n ( n = 7–13) clusters keep basically the analogous frameworks as the low-lying Si n +1 clusters. The relative stabilities of YbSi n ( n = 7–13) clusters are studied, YbSi n ( n = 8, 10, and 13) clusters have stronger relative stabilities in comparison with the corresponding neighbors. Furthermore, the charges in the most stable YbSi n ( n = 7–13) clusters are transferred from Yb atom to silicon frame. Interestingly, the inserted Yb raises the chemical activities, increases the metallic in character of YbSi n clusters. In addition, the most stable charged YbSi n ( n = 8–10, 13) geometries are deformed their neutral geometries.

Characterization of nano-composite oxide ceramics and monitoring of oxide thin film growth by laser-induced breakdown spectroscopy

Multi-component oxide ceramics and epitaxial oxide thin films are analyzed by laser-induced breakdown spectroscopy (LIBS). Furthermore, pulsed-laser deposition (PLD) of thin films is investigated by long-term monitoring of the optical plasma emission. Both nano-composite high-temperature superconductors (HTS) consisting of YBa 2Cu 3O 7 − δ bulk and Y 2Ba 4MCuO x (M-2411, M = Ag, Nb) nano-particles, and semiconducting ZnO doped with Aluminum and Lithium are ablated by nano-second laser pulses. The plasma emission is recorded using grating spectrometers with intensified gated detectors. The LIBS signals of nano-particles correlate with the nominal content of the M-2411 phase (0–15 mol%) and reveal a strong signal of Ytterbium impurity (3–35 ppm). In situ monitoring of the PLD process shows element signals that are stable for more than 10,000 laser pulses for both HTS and ZnO ceramics. The relative concentration of elements in thin films and ceramics as determined by LIBS is almost the same.

Impurity‐related magnetism in the diluted magnetic semiconductors Pb1−xSnxTe:Yb

AbstractThe effect of ytterbium impurity on the magnetic and galvanomagnetic properties of new diluted magnetic semiconductors Pb1−xSnxTe:Yb was investigated. Impurity‐related Curie–Weiss paramagnetism was revealed. The concentration of magnetic centers and the ytterbium impurity‐band occupancy as a function of impurity content were determined. The results are discussed assuming the formation of a ytterbium‐induced level under the valence‐band top and a variation of the magnetic centers concentration due to changing of the mutual arrangement of the valence band, impurity level and Fermi‐level position. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Diffusion of ytterbium in silicon

Diffusion of ytterbium in silicon is studied by the direct method of radioactive isotopes in the temperature range of 1100–1250°C. Diffusion coefficients of ytterbium impurity in silicon are determined.

Electrical properties of silicon layers implanted with ytterbium ions

It is ascertained that implantation of 1-MeV ytterbium ions with a dose of 1013 cm−2 into silicon with subsequent annealing at temperatures of 600–1100°C gives rise to donor centers. The donor-center concentration is higher in the samples implanted additionally with oxygen ions. The results show that at least two types of donor centers are formed; these centers contain either ytterbium or oxygen impurity atoms. The dependence of electron mobility on the concentration of electrically active centers in the silicon layers implanted with the ytterbium rare-earth ions is determined in the concentration range of 7×1015–1017 cm−3.

The 4f Intrashell Transitions of Ytterbium in Indium Phosphide

AbstractZeeman measurements in magnetic fields up to 16 T have been performed on the no-phonon lines labelled #3, #4, and #8 of the spectrum of ytterbium impurities in indium phosphide. A strong polarization effect and changes in intensities were observed. An energy level diagram is presented that satisfactorily explains the magnetic field effect and the relative intensities of the photoluminescence lines and is consistent with experiments described in the literature.

Photoluminescence of superconducting yttrium-barium ceramics with europium, terbium, and ytterbium impurities

Photoluminescence of superconducting yttrium-barium ceramics with europium, terbium, and ytterbium impurities

Electrical properties of ytterbium-doped InP grown by metalorganic chemical vapor deposition

A study has been carried out on the electrical properties of ytterbium-doped InP grown by metalorganic chemical vapor deposition for the purpose of clarifying the electrical behavior of ytterbium impurities in InP. The epilayers were characterized by Hall effect measurements and by deep level transient spectroscopy. The results strongly suggest that ytterbium introduces an acceptor-like level 0.03±0.01 eV below the conduction band which is related to isolated ytterbium atoms or single ytterbium atoms complexed with native defects. No signs of precipitation or clustering of ytterbium are observed for concentrations below 1018 cm−3 . Contrary to previous hypotheses, no evidence has been found for the existence of an ytterbium-related acceptor level in the lower half of the band gap.

X-ray fluorescence spectrometric analysis of erbium oxide for rare earth impurities

An X-ray fluorescence spectrometric method has been developed for the analysis of high purity erbium oxide for the determination of yttrium, terbium, dysprosium, holmium, thulium, ytterbium and lutetium oxide impurities in the concentration range 0.005–0.1%. The sample is taken in oxalate form, mixed with a binder (boric acid) in the weight ratio 3∶1 and made into a double layer pellet. The analysis is done on a Philips PW 1220 X-ray fluorescence spectrometer using a LiF (200) analyzing crystal. The precision at each concentration of the standards and theoretical minimum detection limit for each element has been calculated.

Test of a new polarized hydrogen target (spin refrigerator) as neutron polarizer

Neutron-transmission measurements were made to determine the proton polarization in a single crystal of yttrium ethylsulfate with the aim of exploring its utilization as a spin filter for thermal and epithermal neutrons. The proton polarization is coupled to that of a paramagnetic ytterbium impurity simply by rotating the extremely anisotropic crystal in a magnetic field (spin refrigeration). A proton polarization of 41% was obtained in a helium bath near 1.2 K by rotating a large single crystal at a frequency of 150 ${\mathrm{sec}}^{\ensuremath{-}1}$ in a field of 14.6 kOe. The extrapolation of the results indicates that a proton polarization ${p}_{\mathrm{H}}\ensuremath{\simeq}65%$ can be achieved with relatively simple technology. For this value of ${p}_{\mathrm{H}}$ the spin refrigerator becomes a competitive neutron spin filter.

Exact solution of the degenerate Anderson model

On the basis of the Bethe ansatz solution of the degenerate Anderson model the magnetic susceptibility and orbital occupation number of cerium or ytterbium impurities in a metal are calculated in an explicit form.

Color centers in the ionized and in the triplet state ?Z 2 centers in ytterbium-doped KCl crystals

Z2 centers in Yb2+-doped KCl crystals are investigated by optical absorption experiments and by ESR experiments using the optically excited triplet state. Two mainZ2 center configurations have been found. One of them shows (100) axial symmetry and is optically orientable in the crystal. The other one possesses (110) symmetry elements. The measured fine structure constants are explained partly by dipole-dipole interaction of the two electronic magnetic moments partly by spin orbit interaction due to the Ytterbium impurity. The structure of the optical absorption spectra is attributed to as2−s d charge transfer transition affected by the combined effect of crystal field and spin orbit interaction.

Influence of the crystalline field on the Kondo effect: Cerium and ytterbium impurities

The thermoelectric power and the effect of a magnetic field on the impurity relaxation rate of alloys or compounds with cerium or ytterbium are computed within a model describing both the Kondo and the crystalline field effects.

Effect of a magnetic field on the relaxation rate of ytterbium diluted in gold

The effect of a magnetic field on the relaxation rate of the ground state of ytterbium impurity in gold is computed up to third order in the exchange integrals, within a Hamiltonian which describes the resonant scattering of Ytterbium impurities and takes into account both spin and orbit exchange scattering and crystalline field effect. It is found that the zero-field T ln T behaviour of the relaxation rate disappears completely for only a 10kG field in Au Yb alloys.

Influence of the crystalline field and Kondo effects on the relaxation rate: Application to Mössbauer experiments of ytterbium diluted in gold

M\"ossbauer experiments show that the relaxation rate of the doublet ground state ${\ensuremath{\Gamma}}_{7}$ in $Au \mathrm{Yb}$ alloys, divided by the temperature, behaves logarithmically at low temperatures and rises very quickly above 10 K. This behavior is accounted for by computing the relaxation rate up to third order in the exchange integrals, with a Hamiltonian which decribes the resonant scattering of ytterbium impurities and takes into account both spin and orbit exchange scattering and crystalline field effect.

Temperature Dependence of the Electric Field Gradient at Ytterbium Impurities in Thulium Metal

Time-differential perturbed angular correlations of nuclear $\ensuremath{\gamma}$ rays from the decay of $^{172}\mathrm{Lu}$ to $^{172}\mathrm{Yb}$ have been used to measure the temperature dependence of the electric quadrupole hyperfine interaction at dilute ytterbium impurities in polycrystalline thulium metal over the temperature range from 77 to 560 K. The dependence on temperature is found to be relatively weak and almost linear. Based on a value for the quadrupole moment of the 79-keV state obtained from Coulomb-excitation transition probabilities, the electric field gradient (EFG) is (6.15 \ifmmode\pm\else\textpm\fi{} 0.15) \ifmmode\times\else\texttimes\fi{} ${10}^{17}$ V/${\mathrm{cm}}^{2}$ at 77 K, and decreases with increasing temperature by (6.6 \ifmmode\pm\else\textpm\fi{} 0.6) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ ${\mathrm{K}}^{\ensuremath{-}1}$ of the extrapolated value of ${V}_{\mathrm{zz}}(0 \mathrm{K})=6.33\ifmmode\times\else\texttimes\fi{}{10}^{17}$ V/${\mathrm{cm}}^{2}$, with some evidence of leveling off above 500 K. Such a linear temperature dependence is inconsistent with any appreciable contribution to the EFG from an open $4f$ shell, and thus the ionic state of the ytterbium ion is dipositive. The observed EFG is thus due to contributions from the crystal-field and conduction electrons. The temperature variation of the lattice EFG comes mainly from the anisotropy of thermal expansion between the $c$ axis and the basal plane of the thulium lattice. Estimates based on point-charge calculations of the crystal field combined with measured thermal-expansion coefficients yield a magnitude and temperature dependence that are both too small to explain the observed results on this basis. The remaining temperature dependence is ascribed to the effects of local conduction electrons near the Fermi surface.