On the early stage F coloration in lithi[um fluoride doped with divalent cation impurites

Abstract

Using γ-ray irradiation at different temperatures and fluxes, we obtain new information on the early stage F-coloration of LiF which can be easily interpreted in terms of the Crawford mechanism.     

Electron-trapping centers in additively colored alkali halide crystals doped with divalent impurities

A study has been made of the temperature dependences of the dielectric loss and structure-sensitive conductivity of additively colored KCl single crystals having a Sr²⁺ impurity. The optical absorption spectra were recorded before and after heat treatment of the colored crystals. A model for Z-centers is proposed on the basis of the results.Translated from Izvestiya VUZ. Fizika, No. 10, pp. 26–29, October, 1969.In conclusion the author thank Professor E. K. Zavadovskaya for suggesting thistopic and for discussion of the results.     

First stage coloration of alkali halides doped with M2+ impurities that change their valence state by irradiation as a function of X-irradiation dose rate

The amount of room temperature first stage coloration of ten alkali halide systems, i.e., NaCl:Pb, NaCl:Co, NaCl:Mg, NaCl:Sn, NaCl:Fe, KCl:Eu, KBr:Eu, KI:Eu, RbCl:Eu and RbBr:Eu has been analyzed as a function of X-irradiation dose rate. In all systems the amount of first stage coloration was found to be proportional to the square root of irradiation dose rate. These results are in very good agreement with the prediction of the theoretical model recently developed by our group to account for the F-center production in alkali halides doped with doubly valent impurity ions that change their valence state by irradiation and give evidence of its validity.     

Dose rate dependence of carrier mobility

The trap-modulated steady-state carrier mobility in insulators depends on the relation between free and trapped carriers. Under irradiation this relation changes due to the radiation-induced shift of the Fermi level. Therefore mobility is a function of dose rate. This function can be calculated when the radiation-induced steady-state conductivity is given as a function of dose rate. If the latter is given by a power law, the former is also given by such a law.     

CaSO4∶Eu磷光体的热释光特性研究

用热释光三维发光谱仪和蓝色滤光片的热释光仪测定了CaSO4:Eu2+的辐照后的发光曲线,得到峰温为107和144℃波长390nm的发光峰.辐照50d后,107℃发光峰已衰退,发光曲线呈现144℃单个发光峰.经一级力学方程式拟合得到的激活能E=(1.02±0.03)eV与初始升温法(1.07±0.01)eV和峰形法(1.02±0.01)eV的非常符合.用通用级动力学模型拟合发光曲线,得到陷阱能级E=(1.04±0.01)eV,频率因子s=(2.07±0.8)×1012s-1和动力学级数b=1.05±0.02 关键词： CaSO4∶Eu 剂量响应 动力学参量 热释光     

Charge Kondo anomalies in PbTe doped with Tl impurities

We investigate the properties of PbTe doped with a small concentration x of Tl impurities acting as acceptors and described by Anderson impurities with negative onsite correlation energy. We use the numerical renormalization group method to show that the resulting charge Kondo effect naturally accounts for the unusual low temperature and doping dependence of normal state properties, including the self-compensation effect in the carrier density and the nonmagnetic Kondo anomaly in the resistivity. These are found to be in good qualitative agreement with experiment. Our results for the Tl s-electron spectral function provide a new interpretation of point contact data.     

Association energy of divalent and monovalent impurities with edge dislocations in NaCl

In the present paper calculations have been made of the association and interaction elastic energies for monovalent cation impurities and divalent cation impurities unassociated and associated with cation vacancies in the form of dipoles with dislocationsa/2 r _{+ +} < r_{Ca ^{+ +}} r_{ + + }< r_{Ca^{ + + } } in the compressed region of dislocation, mainly on the dislocationa/2110 {100}. In the case of divalent impurities associated with cation vacancies in the form of dipoles the increase in impurity concentration can take place at all impurities as in the above mentioned case and additionally Sr⁺⁺

Influence of divalent cationic impurities on plasticity of AgCl

The hardening effect of Mg²⁺, Ca²⁺, Sr²⁺, Cd²⁺ and Ba²⁺ impurities in polycrystalline AgCl was investigated. With exception of Mg²⁺ the hardening effect of the impurities decreases with increasing atomic number (atomic weight). The hardening effects of Mg²⁺ and Ca²⁺ are expressively stronger than those of the three remaining impurities. Approximately linear dependence of the stress at the beginning of plastic deformation on the impurity concentration was found. Possible causes of the different hardening effects of the divalent impurities are discussed.     

Electrophysical properties of epitaxial gallium arsenide doped with acceptor impurities

Epitaxial layers of gallium arsenide doped with zinc and cadmium were grown in a chloride vapor-transport system using diethylzinc and dimethylcadmium as the sources of the impurity. We studied the effect of the inlet pressure of the impurities and the growth temperature on the doping level of the layers. We investigated the temperature dependences of the hole concentration and mobility in layers doped with zinc and cadmium up to different levels.V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 54–58, February, 1995.     

Spectroscopic properties of magnesium aluminosilicate glass-ceramics doped with divalent cobalt ions

Electronic absorption and luminescence spectra and nonlinear optical properties of magnesium aluminosilicate glass-ceramics doped with divalent cobalt ions are studied in relation to their synthesis conditions. The lifetimes of the ⁴ T ₁(⁴ P) and ⁴ T ₁(⁴ F) excited levels of tetracoordinate Co²⁺ ions in these glass-ceramics are found to depend on the cobalt concentration and lie within the ranges from 25 to 40 and from 120 to 450 ns, respectively. Using the absorption saturation curves, the ground state absorption cross section for the wave-length of 1.54 μm is estimated to be σ_GSA=3.3×10^?19cm². The induced emission of the tetrahedrally coordinated Co²⁺ ion, which dominates over the absorption from the excited state in the spectral range from 640 to 690 nm (⁴ T ₁(⁴ P)→⁴ A ₂ transition), is found.     

New aspects on the dielectric properties of the alkali halides with divalent impurities

Dielectric losses were measured in the following crystals NaCl+ (Mg²⁺, Co²⁺, Ni²⁺, Sr²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cd²⁺, Ba²⁺, Pb²⁺), KCl + (Ca²⁺, Sr²⁺, Ba²⁺, ²⁺, Pb²⁺) and KBr + (Sr²⁺, Ba²⁺) in the frequency region 5–500 kHz. It was found that when the divalent cation impurity has an electronic configuration similar to the inert gases (1) no observable deviation from simple Debye theory exists (2) the activation energy Φ increases linearly with the ionic radius of the impurity.The above observations (1) and (2) do not hold when the divalent cation impurity has d-electrons in the outer subshell.     

Photoluminescence of AgGaS2 and CuGaS2 doped with rare-earth impurities

Photoluminescence (PL) related to rare-earth (RE) impurities (Ho, Er and Eu) in AgGaS₂ and CuGaS₂ crystals has been studied. In Ho-doped AgGaS₂ and CuGaS₂, two series of PL lines are observed in 1.86–1.92 eV region and 2.24 eV region, and they are assigned to ⁵F₃–⁵I₇ and ⁵S₂–⁵I₈ transitions of the Ho³⁺ ion, respectively. Similarly, in Er-doped AgGaS₂ and CuGaS₂, Er³⁺-related two PL series are observed: 1.83–1.88 eV region (⁴F_9/2–⁴I_15/2) and 2.22–2.26 eV region (⁴S_3/2–⁴I_15/2). For both Ho and Er impurities, the profile of the PL spectrum in AgGaS₂ is complex, and PL exhibited large number of lines compared with that in CuGaS₂. The differences in PL spectra between this two compounds are related to the crystal field at the cation site and the local atomic arrangement of the RE impurities. This work also refers to the PL band at 2.28 eV observed for the Eu-doped AgGaS₂ crystal.     

A new magneto-optical effect in birefringent crystals doped with paramagnetic impurities

The influence of a strong pulsed magnetic field on the birefringence of crystals has been investigated experimentally. A new magneto-optical effect has been found for the first time: the change in the optical indicatrices of birefringent quartz crystals and potassium yttrium and potassium gadolinium tungstates doped with paramagnetic impurities (iron for quartz and ytterbium for tungstates) under a single pulse of a magnetic field with an induction of 40 T. These changes are retained for a long time after switching off the magnetic field and appear to be irreversible.     

Impurity photovoltaic effect in silicon solar cells doped with two impurities

In this work, a numerical study has been carried out to investigate the impurity photovoltaic (IPV) effect for silicon solar cells doped with two impurities (indium and thallium). It is found that the conversion efficiency \(\eta \) of the IPV solar cell doped with two impurities can improve by 2.21 % absolute, which is greater than that of the IPV solar cell doped with indium ( \(\Delta \eta =1.63\,\%\) ), but less than that of the one doped with thallium ( \(\Delta \eta =2.69\,\%\) ). It is concluded that introducing two IPV impurities may not be a good selection for implementing the IPV effect since one impurity with poorer IPV effect can absorb some sub-bandgap photons while contributing fewer currents. The location of impurity energy level is critical to the IPV cell performance. For an acceptor-type IPV impurity, the optimized location of the IPV impurity energy level locates at 0.20–0.26 eV above the valence band edge. Our results may help to make better use of the IPV effect for improving solar cell efficiency.     

SIMS diagnostics of the structure of nanometer-sized semiconducting layers doped with impurities

The possibility of analyzing the structure of nanometer-sized silicon layers doped with boron and antimony (at a concentration level of 10⁻²–10⁻³ at %) via secondary-ion mass spectrometry (SIMS) is investigated. A recoil-atom implantation process has been evaluated from the standpoint of its contribution into the total recorded signal of secondary ions of impurities. It is demonstrated that SIMS can be used for qualitative determination of the structure formed in doped δ-layers.     

Stability and electronic properties of carbon nanotubes doped with transition metal impurities

We apply first-principles method to investigate the effect of the diameter on the stability and electronic properties of zigzag carbon nanotubes doped with iron, nickel and manganese impurity atoms. In this contribution we follow the evolution of the electronic and structural properties as a function of the nanotube diameter. As a general result, we found that the binding energy decreases with the increasing nanotube radius. Additionally, depending on the interaction of transition metal impurity with the tubular carbon structure, it is observed that the total magnetization varies with the tube diameter due to hybridization and confinement effects. It is also shown that such magnetization varies with the curvature radius, increasing for manganese impurity atoms and decreasing for iron and nickel.     

Characteristic interactions of 111Cd probes with nonradioactive In impurities doped in ZnO

Local structures produced in 0.5 at.% In-doped ZnO were investigated by means of the time-differential perturbed angular correlation method using the ¹¹¹Cd probe nuclei generated in the disintegration of different parents, ¹¹¹In and ^111mCd. From distinct perturbation patterns obtained with the probes descended from the different parents, it was ascertained that the doped In atoms locally form a unique structure dispersed in ZnO matrix without forming macroscopic agglomerates of their own.     

Superparamagnetic behaviour of cement clinker and its ferrite phase doped with different impurities

Two oxide mixtures of clinker and its ferrite phase of compositions (66.5 wt.% CaO+24.5 wt.% SiO₂+6.0 wt.% Al₂O₃+3.0 wt.% Fe₂O₃) and (60.4 wt.% CaO+15.4 wt.% Al₂O₃+24.2 wt.% Fe₂O₃) respectively were divided into protions and were mixed individually with 0.5, 1, 1.5 or 3 wt.% of LiF, MgF₂, CaF₂, CaCl₂ or ZnO. Each portion of clinker was fired at 1450°C and each portion of ferrite was fired at 1350°C for 30 min. then quenched in air. Mössbauer effect and X-ray diffraction measurements were performed on each sample. The impurities doping produced small particle size. The LiF doping gave the smallest particle size and the highest blocking temperature. The ferrite with LiF exhibited two Fe³⁺ sites while the other used impurities gave one site only. The superparamagnetic relaxation appeared only in the spectra of ferrite with impurities, which means that the impurities in clinker have a tendency to combine with the calcium silicate phases not with C₄AF.