EPR Study of Nd3☎ Ions in β-BaB2O4 Single Crystals

An Electron Paramagnetic Resonance (EPR) study of Nd^3? ions in single crystals of the low-temperature phase of barium borate (β-BaB₂O₄ or BBO) is presented. The EPR spectra show the existence of a minimum of three different Nd^3? centres. The g-matrices for three of the centres have been determined from the analysis of the angular dependencies of the spectrum in two planes of the crystal. This study allows us to conclude that neodymium is incorporated in the low-symmetry Ba^2? site. Possible reasons for the appearance of various Nd^3? centres are discussed.     

Structural,Magnetic and Optical Properties of Rh2☎ Centres in NaCl Lattices: An Explanation

A method for exploring Jahn—Teller systems in the framework of Density Functional Theory is described in the present work. Using such a method the properties of the Rh^2? centre in NaCl with remote charge compensation are studied. The calculations support the existence of a strong Jahn—Teller effect and account reasonably for the main features of EPR and optical spectra. The onset of charge transfer excitations is calculated to be at about 3.7 eV a fact which concurs with available experimental data. The elongated geometry is found to be about 200cm^?1 more stable than the compressed one in agreement with experiments.     

Electrical and Optical Properties of Bulk ZnO Single Crystal Grown by Flux Bridgman Method

Zinc oxide （ZnO） single crystals are grown by the modified vertical Bridgman method using a PbF2 flux. The maximum size of the as-grown ZnO crystal is about Φ25 mm×5mm. The transmittance of the as-grown ZnO crystal is more than 70% in the range of 600-800hm and the optical band gap is estimated to be 3.21eV. The photoluminescence spectrum indicates that the as-grown ZnO crystal has a very low concentration of native defects and is much closed to its stoichiometry. The electrical measurement exhibits that the ZnO crystal has low electrical resistivity of 0.02394Ωcm^-1 and a high carrier concentration of 2.10×10^18cm^-3.     

Comparative Studies of Er3☎ Ions in LiNbO3 Waveguides Produced by Different Methods

We compare the optical properties of Er^3? in LiNbO₃ waveguides produced by different techniques and find by confocal luminescence microscopy characteristic differences in the excitation and emission transitions. Besides a small redistribution among the regular defect sites, essentially no direct Er^3?—Ti^4? interaction can be observed in Ti^4? diffused waveguides. However a significant shift in transition energies is found, which increases with Ti^4?concentration. Based on earlier results we associate this shift with a decrease in the intrinsic electric field. In addition to a similar shift, we find in Zn^2? diffused waveguides new defect types which suggest a change in direct environment. Finally, in annealed proton exchange waveguides we find no interaction effects at all.     

First-Principles Studies on the Electronic Structures and Optical Properties for the PbWO4 Crystal Containing V^2-pb

The electronic structures, dielectric functions, complex refractive indices and absorption spectra for a perfect PbW04 (PWO) crystal and the PWO crystals containing lead vacancy V^2-pb have been calculated using a full-potential (linearized) augmented plane-wave (LAPW) local orbitals (LO) method with the lattice structureoptimized. The peaks of the absorption spectra corresponding to the electronic transitions have been studied.     

Anisotropic Scattering in BaTiO_3: Ce Single Crystal

InPastdecadesseveralformsoflight-inducedscatteringhavebeenobservedfromBaTiossinglecrystali1luminatedbyalinear,polarizedlaserbeam[1~7j.Ingeneral,thescattteringPatterncanbeisotropicoranisotropicdependingonthepropagationdirectionofthelightbomrelativetothecrystallographicaxesandthebeampolarization,itiscom-monlyacceptedthatthephysicaloriginofthisphenomenonistherandomrecordingofParasiticgratingswrittenbyanincidentbeamanditsscatteredbeamfromcrystalinhomo-geneities[1J.Recently,anewtyPeofnonlinearopt…     

Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal

Mn doped ZnO bulk single crystals are grown by the modified Bridgman method. The as-grown crystals are red in eolour. The additional Raman mode observed at 524cm^-1 is attributed to the Mn ions incorporating into ZnO crystal. The crystal exhibited paramagnetie under lower applied field below 2280 Oe. Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dominant under applied field above 5270 Oe. The magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetie characteristic under an applied field of 2kOe. No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal.     

Mode Exciting Properties of Photonic Crystal Fibres with the Optical Field Incident from a Single Mode Fibre

We numerically investigate the mode exciting properties of photonic crystal fibres by using the beam propagation method when the optical field is input from a traditional single mode fibre. The results show that both the excited mode spectrum and the coupling-efficiency of each excited mode depend on the normalized pitch А/λ and the normalized hole-size А/λ. Furthermore, we obtain the boundary profile of the optimizing coupling-efficiency for the excited fundamental mode： the boundary （А/λ）＊ is linear to the boundary （А/λ）. All of these will pave the way for smoothing applications of photonic-crystal fibres, such as splicing and designing photonic-crystal-fibre functional devices.     

Optical Constants of an Apatite Single Crystal in the IR Range of 6–28 μm

On the basis of polarized IR-reflection spectra in the range of 5000–350 cm^–1 measured from the natural face of an optically transparent fluorapatite single crystal, components of a complex refractive index (optical constants) for radiation-vector orientations E ‖ c and E ⊥ c have been calculated by the Kramers–Kronig method. The fluorapatite single crystal has been chosen from several samples: it contains a minimum amount of impurities and has a high degree of crystallinity in accordance with the criteria of IR spectroscopy and Raman spectroscopy. Tabular data on optical constants for ordinary and extraordinary rays are given for the IR range of 6–28 μm. The obtained absorption spectra are compared with the results of quantum-chemical ab initio calculations within the B3LYP simulation.     

Incommensurate Phases of the MgSiF6·6H2O Crystals: EPR and Group-Theoretical Studies

The group-theoretical study of the structural phase transition to incommensurate state of MgSiF₆·6H₂O crystals, revealed by the electron paramagnetic resonance (EPR) method, as well as analysis of the EPR results, are presented. The consideration of temperature dependences of Mn²⁺ admixture ion EPR spectrum symmetry and parameters leads to the conclusion that at T _i1 = 370 ± 0.3 K they undergo second-order structural phase transition to incommensurately modulated state, the order parameter of this transition may be the angle of [Mg(H₂O)₆]²⁺ octahedra rotation around crystal C ₃ axis. At temperature decreasing below T _i1 the gradual transformation of plane-wave modulation of lattice displacements into soliton mode occurs, which is interrupted by the first-order phase transition at T _i2 = 343 ± 0.3 K accompanied by abrupt decrease in modulation amplitude. At T _c = 298.5 ± 0.3 K the first-order improper ferroelastic phase transition into monoclinic phase occurs. The group-theoretical analysis of the phase transition at T _i1 in the investigated crystals, carried out for the first time, has shown that the existence of the incommensurately modulated phase is conditioned by the fundamental reasons (presence of Lifshitz invariant). The conclusions of this analysis on the nature of order parameter, the structural motifs of incommensurate phase and the possible character of temperature evolution of the structure are in agreement with the EPR investigation data.     

Preparation and Photoemission Spectra of Rb3C60 Single—Crystal Thin Films

Rb3C60 single-crystal thin films were prepared on the cleaved (111) surface of C60 single crystal.The photoemission spectrum line shapes of the lowest unoccupied molecular orbital (LUMO) derived band at room temperature and 150K were established by synchrotron radiation photoemission spectrum measurements.The density of states near the Fermi level was distinctly affected by temperature.No less than six sub-peaks of the LUMO band were observed even at room temperature.The existence of so many sub-peaks offered the opportunities to analyse in more detail the orientational structure and the electron-Boson interactions of the narrow-band metallic Rb3C60.     

Single Crystal Si Layers on Glass Fabricated by Hydrophilic Fusion Bonding and Smart-Cut Technology

A single crystal Si thin film on a glass substrate has been obtained successfully by hydrophilic fusion bonding and the smart-cut technology. Tensile strength testing shows that the bonded interface has strong adhesion and the bonding strength is about 8.7MPa. Crystallinity and microstructure of the samples have been characterized by transmission electron microscopy (TEM). Electrical properties have also been investigated by Hall measurements and four-point probe. The mobility of the transferred Si layer on glass is about 122cm^2//V.s. The results show that the single-crystal silicon layer transferred onto glass by direct bonding keeps good quality for the applications of integrated circuits, transducers, and fiat panel display.     

Distribution of Mn2+ Manganese Ions in a Single Crystal of the Lithium–Gallium Li0.5Ga2.5O4 Spinel

Physics of the Solid State - A self-organization of eight structurally and magnetically nonequivalent positions of manganese Mn2+ ions in the unit cell of a single crystal of the...     

Photogalvanic Currents and Electrical Inhomogeneity of a 2D Structured Single Crystal of Ferroelectric–Semiconductor

Physics of the Solid State - The experiment, which makes it possible to clarify the mechanism of formation of electrical inhomogeneity of a TlGaSe2 crystal, is described. Evolution of the anomalous...     

Optical characteristic and gap states distribution of amorphous SnO2:（Zn,In） film

In this paper the fabrication technique of amorphous SnO 2:(Zn,In) film is presented.The transmittance and gap-states distribution of the film are given.The experimental results of gap-states distribution are compared with the calculated results by using the facts of short range order and lattice vacancy defect of the gap states theory.The distribution of gap state has been proved to be discontinuous due to the short-range order of amorphous structure.     

Optical properties of (F2 +) H centers in NaCl:OH− crystals

Abstract

In this work we present new data on the formation and destruction of the laser active (F₂ ⁺)