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The strain dependence of the free-exciton resonance energies in AlN epilayers and the values are analyzed by using an appropriated Hamiltonian assuming equibiaxial stress for the wurtzite crystal structure in order to obtain valence band parameters. The strain dependence of the valence band ordering, optical transition probability and free-exciton binding energy are analyzed.

A solid-solid transition occurring at 191 degree Celsius from [alpha]-4T/LT to [alpha]-4T/HT is demonstrated to obtain large and thick [alpha]-4T/4T/HT single crystals preserving the overall crystallinity of the starting [alpha]-4T/LT single crystals grown by the floating-drop technique. The result suggests that the method is useful to obtain large single crystals of the high temperature polymorph through a simple controlled heating treatment performed on solution-grown single crystals of the low temperature polydmorph.

A tunable Mach-Zehnder interferometer with two-dimensional photonic crystal structure is described by using copper oxide high-temperature superconductor. The simulation results for this interferometer have shown that the light transmission can be modulated with different temperature distributions.

A study was conducted to investigate the crystal structure and electrical properties of CeAl[O.sub.3] ceramics prepared by the mixed oxide route. The intrinsic dielectric behavior is established using impedance spectroscopy and the microwave dielectric properties of dense CeAl[O.sub.3] ceramics are reported.

The crystal structure and dielectric response of lead-free tetragonal tungsten bronze, Sr(sub)2LaTi(sub)2Nb(sub)3O(sub)15 (SLTN) ceramics was studied in a very broad frequency and temperature range. The results show that the ceramics have a relaxor-like behavior that can be generally explained in the framework of polar nanocluster dynamics concept, with some peculiarities in the dielectric response, relaxational and crystal lattice dynamics.

Saturated domain orientation textures of three types of pseudocubic ferroelectric ceramics, after complete electric and uniaxial tension poling are studied. The findings show that macroscopic symmetrics of ferroelectric crystals change from tetragonal, rhombohedral and orthorhombic single crystals to transversely isotropic completely poled ceramic.

The structural, magnetic, and magnetocaloric properties of the Cu-substituted perovskite manganites [La.sub.1-x][Pb.sub.x]Mn[O.sub.3] single crystals, where x ~ 0.14, are analyzed. The results are described based on the competing effect between the double-exchange interaction and the lattice distortion induced by Cu doping.

Valence electron energy loss spectroscopy (VEELS) and high resolution transmission electron microscopy (HRTEM) are performed to investigate different Hf[O.sub.2] thin films grown on Si (001). The results have shown that VEELS is a relevant tool to access structural, chemical and electronic properties at a subnanometer scale, when it is performed in a high resolution transmission electron microscope.

Magnetic properties and structural separation of [La.sub.0.7][([Ca.sub.1-y][Sr.sub.y]).sub.0.3] Mn[O.sub.3] thin films were investigated. The results reveal that the films with 0.3

Synthesis of monocrystal aluminum nitride nanowires was carried out at low temperature through direct reaction of Al[Cl.sub.3] with Na[N.sub.3] in a non-solvent system at low temperatures. The nanowires show long straight-wire morphology and are pure monocrystal hexagonal or face center structure having relatively narrow emission peak.

A combination of scanning electron microscopy (SEM), atomic force microscopy (AFM) and various other techniques is employed to study the structural, magnetic and electrical properties of large La-Sr-Mn-O single crystals grown by the floating zone technique. The analysis of the correlation between the structural defects and properties of such crystals show that unlike the electrical properties, the magnetic ordering of the domains is strongly affected by the amount of defects present in the crystals.

The effective medium theory is employed to reduce the two-dimensional photonic crystals to an effective one-dimensional model, which is then used to predict the dispersion in the long and short wavelength limits. The analysis of the electromagnetic fields propagating in photonic crystals shows complete agreement between the theoretical and experimental results, which can then be used for further studies and developments.

The study presents a theoretical, as well as an experimental analysis of the water-steel phononic crystals with triangular and honeycomb lattices, which consist of various complete band gaps and deaf bands in them. The results of the analysis demonstrate that the symmetry reduction leads to the opening of the first complete band gaps for the honeycomb lattices, which is not found in the triangular ones.

A two-color (ultraviolet and near-infrared), femtosecond, pump-probe spectroscopic technique were used to observe time-resolved intervalley transitions of electrons between the conduction band [Gamma] and L valley in GaN single crystals. It was found that the threshold for the [Gamma] L transition appears at the energy of 4.51 [plusminus] 0.05 eV and the electron scattering time from the [Gamma] to L valley is comparable to the 170 fs width of our pump pulses, while the return process f electrons from L to [Gamma] is measurably slower.

The near infrared emission is characterized at 1.84 [micro]m of thulium ions in KGd[(W[O.sub.4]).sub.2] (KGW) single crystals codoped with [Yb.sup.3+] and [Tm.sup.3+] ions by pumping at 940 nm. The reciprocity method is used to calculate the 1.84 [micro]m emission cross section from the absorption cross section.

The electro-optic response of the defect mode switching in the one-dimensional (1D) photonic crystals (PC) with the nematic liquid crystals (NLC) defect layer is analyzed by considering the molecular director distributions in the defect layer. The calculated defect mode switching has displayed a response in the order of microseconds, despite using the reorientation of NLC.

X-ray diffraction (XRD), high resolution electron microscopy (HREM) and electron holography are used to investigate the structure and the remanent state of individual [alpha]-Fe nanoparticles encapsulated in carbon nanotubes (CNTs). The results have shown that the saturated magnetization of the [alpha]-Fe nanorod with a CNT outer shell is close to that of bulk pure [alpha]-Fe, indicating that the core-shell nanostructure prevented the surface oxidation that has degraded the magnetic properties of nanostructured [alpha]-Fe.

Epitaxial silver tantalate niobate, Ag([Ta.sub.0.5][Nb.sub.0.5])[O.sub.3] (ATN), thin films on (001)SrRu[O.sub.3]/(001)LaAl[O.sub.3] substrates are deposited by a chemical solution deposition method. The crystal structure and dielectric properties of (00l) epitaxial ATN films on (001)SrRu[O.sub.3]/(001)LaAl[O.sub.3] (SRO/LAO) substrates are examined.

Various studies are conducted to study and understand the coupling properties of the localized surface modes, which are induced between two identical truncated triangular photonic crystals, composed of air holes in a dielectric background. The results from the finite-difference time-domain simulation demonstrate that the localized mode with even parity act as a good-guided mode.

The study focuses on the steady-state emission properties of infiltrated flurophores, which are also highly affected by a well-designed passband in the stop band of self-assembled colloidal photonic crystal superlattces. The results obtained from the analysis are extremely useful, as they lead to the development of all-optical integrated circuits because of its ability of lowering the threshold for lasing by spectrally narrowing the emission of fluorophores.

Various experiments are conducted to observe the characterization of guided resonances in two-dimensional photonic crystal slabs. The analysis indicates that phase spectra exhibit the signatures of guided resonance, the spectrum of which can be changed to change the incident angle of the input beam.

A new atomic structure-based model is developed for high-temperature lattice conductivity for compact, as well as cage-bridge crystals, which is used to estimate and measure the Gruneisen parameter and the lattice thermal conductivity of the crystals. The results give a detailed study of the structural metrics of the crystals with low, as well as high lattice conductivity and hence can be used as a guide for designing of new materials with desired lattice conductivity.

A model that allows composites containing constituents that undergo phase transitions when they are dynamically loaded is developed. The effect of local microstructure on the macroscopic stress-strain and thermodynamic response of the SiC-Ti composite is investigated for different orientations of loads relative to the fiber axes.

High quality films of vanadium oxide (V[O.sub.2]) are processed by pulsed laser deposition, which were grown epitaxially on (0001) sapphire substrate through domain matching epitaxy, involving the match of integral multiples of lattice planes between the film of monoclinic structure and the sapphire substrate. These high quality epitaxial films exhibit a sharp transition, a large resistivity or optical reflectivity amplitude and a very small hysteresis, similar to bulk single crystals of V[O.sub.2].

The X-ray diffraction measurements on Mn[Ga.sub.2][Se.sub.4] compound are made as a function of pressure up to 25 GPa. The results have shown that near 3 GPa there is a symmetry change from an ordered tetragonal to a disordered tetragonal pseudocubic structure.

The dependence of structural and magnetic properties of MnAs epilayers on GaAs(111)B is investigated with respect to specific growth parameters. The influence of selected growth parameters on the surface morphology, the quality of the crystalline structure, and the magnetic properties of MnAs is analyzed.

The effective biaxial modulus of ideally (hkl)-fiber-textured films is studied for the cases where the constituent grains are of hexagonal, tetragonal, and orthorhombic crystal symmetries. The coincidences of the Voigt and Reuss averages of M are explained in terms of the symmetry of the constituent grain about the fiber axis and the results have indicated that the Voigt-Reuss-Hill average is a good theoretical estimation.

An investigation on the crystal structure and thermoelectric properties of type-I clathrate compounds in the Ba-Ga-Ge system is conducted as a function of Ga content. The absolute values of electrical resistivity and Seebeck coefficient increase, while that of lattice thermal conductivity decreases with the increase in the Ga content.

A theory of three-dimensional (3D) magnonic crystal is developed and applied to explain the existence of the spin-wave frequency gap, recently revealed by neutron scattering experiments. A confrontation of the theory with experimental results proves that certain manganites could be regarded as 3D magnonic crystals existing in the nanoscale in nature.

A study is conducted to show that the films grown on MgO (100) substrate remain fully coherent up to much greater thickness than predicted by the FKR model (70 nm) from the strain relaxation studies of epitaxial Fe3O4 thin films grown on MgO (100) substrates. The observed strain relaxation behavior is attributed to the differences in the crystal structure symmetry between MgO and Fe3O4.

The domain inversion in RuO2:LiNbO3 crystal wafer by the digital holographic interferometry is quantitatively studied. The crystal wafer is placed into one arm of a Mach-Zehnder-type interferometer to record a series of holograms. An unexpected phase contrast adjacent to the domain wall is measured and the influence of the external voltage on it is studied.

Study is presented to find out the dependence of the dielectric response of the material on the crystal microstructure, that is, on the size of the domains, providing information, which can contribute to the understanding of the origin of the very high dielectric permittivity in perovskite materials. Several dielectric functions and their variation with the frequency and/or the temperature are analyzed.

A detailed study of the structure and magnetic properties of V/Co versus Co/V bilayers grown on MgO(001) substrates with cubic and hexagonal Co crystal structures is presented. Co is found to adopt fcc structure when grown on MgO(001), while it adopts hcp structure when grown on V(001).

The orientation of crystals of the giant magnetostrictive compound Terfenol-D solidified in a static magnetic field is investigated. Experimental results show that on the condition of slow cooling in the presence of a static magnetic field, free crystal nuclei of these materials in high temperature melt are easily be induced and aligned with their easy magnetic axes along the field at the beginning of the solidification.

Relaxor-type ferroelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) films, 2-3 mum in thickness, with a PbTiO3 content (x) ranging from 0 to 1 were grown on [(100).sub.c]SrRuO3 ll (100)SrTiO3 substrates at 650 degree Celsius by metal-organic chemical vapor deposition. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase, with increasing x.

Polycrystalline BiM[n.sub.2][O.sub.5] and B[i.sub.0.9]C[e.sub0.1]M[n.sub.2][O.sub.5] are prepared by a solid-state reaction. A crystalline structure study shows that all x-ray diffraction patterns could be indexed successfully in an orthorhombic phase.

High density, almost impurity-free and defect-free barium titanate (BaTiO3) fine particles with various sizes from 20 to 1000nm are prepared by the two-step thermal decomposition of barium titanyl oxalate and postheating treatment. The results suggest that the phase transition behavior of the BaTiO3 nanoparticles is quite different from that of the BaTiO3 single crystals.

Chromium dioxide (CrO2) is synthesized by direct combustion process between Cr and O2 in a diamond anvil cell at 14 GPa using laser heating. It is concluded that X-ray diffraction and Raman spectroscopy studies evidenced a structural phase transition in CrO2 from rutile-type to CaCl2-type at about 17GPa.

Polarized Raman scattering and infrared reflectivity measurements are used to investigate the crystal structure of Czochralski-grown NaLaF4 single crystals. It is concluded that the analysis of the symmetries of the observed optical phonon modes, beside piezoelectric resonance spectra, allowed to identify the P6 group as the correct one presented by this material at room temperature.

A method to simplify simulation techniques for determining liquid-crystal director orientation in geometrics is presented with sharply defined edges and for surfaces with strong anchoring without preferred direction. It is shown analytically that close to such edges, the liquid crystal can be described by just a few parameters.

Experimental procedures for evaluating the compositional homogeneity of LiNbO3 single crystals were developed using the ultrasonic material characterization system and the true congruent composition was determined. Also provided were absolute relationships among V(sub LSAW) chemical composition and acoustical physical constants.

An analysis is presented of the optical properties of photonic woodpile structures. Large superprism phenomena inside polymeric woodpile structures having a refractive index of less than n=1.6 is demonstrated.

PbS nanocrystals are synthesized by annealing a sulfur-implanted Pb-containing silicate glass. This method improves control over nucleation and growth and it is demonstrated by the impact on the PbS nanocrystal photoluminescence (PL) properties of progressively replacing CaO by ZnO in a S-implanted Pb glass.

Mg(sub x)Zn(sub 1-x)O layers with different crystal structures due to different Mg contents are grown on a MgO/Al2O3(0001) template. The results images demonstrate that the epitaxial orientation of Mg(sub x)Zn(sub 1-x)O films with less than or equal to 0.65 on the MgO buffer layer initially is along [111] cubic direction and then changed to [0001] wurtzite direction.

A study is carried out on the crystal structure and dielectric properties of (1-x)Pb(Yb1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3 (PYN(1-x)PSNx) (O less than or equal to x less than or equal to 0.60) solid solution. Details of its pseudobinary phase diagram are determined.

The grating translation technique (GTT), which employs a momentary shift of light fringes during holographic recording, is a powerful tool for characterization of nonlinear materials. The introduction of a frequency detunes between the light beams and modifies strongly the nonlinear response.

The optical properties of lithium niobate single crystals are quantitatively calculated at different temperatures. The present work shows a clear relation among the crystal structure, optical properties, and temperature in lithium niobate single crystals.

The effective properties associated with the propagation of electromagnetic waves in photonic crystals (PCs) are analyzed for one-dimensional photonic crystals to illustrate the difference in those properties between infinitely extended and finite size photonic crystals. The results clearly demonstrate the importance of the two end faces on the effective properties of a finite size PC, which can be quite different from those deduced for an infinitely extended PC.

The materials with large magneto-optical (MO) Kerr rotation are of interest for development of recording media. The structure-dependent electronic effects on the magnetic and magneto-optical (MO) properties of equiatomic CoPt alloy with L1(sub 0), L1(sub 1), and randomly disordered structures in ab initio band-structure calculations are reported.

Results demonstrate that there is no distortion of the lattice or the groups in the Yb-doped yttrium orthovanadate (YYV) crystals as revealed by Raman spectral analysis. Data further point out that YYV crystals serve as crystal field for measuring dopant ion species with lasers.