Materials Literature
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Capacitance relaxation in Ba0.8Sr0.2TiO3 thin film structures has been investigated. Slow decrease of the capacitance after a bias voltage switching on is explained by suppressing the film dielectric permittivity by the field of a p-n junction originated as a result of the oxygen vacancy migration in the bias field. A…
Multilayers of anisotropically nanostructured silicon (Si) have been fabricated and studied by polarization-resolved reflection measurements. Alternating layers having different refractive indices exhibit additionally a strong in-plane anisotropy of their refractive index (birefringence). Therefore, a stack of layers,…
Face-centered tetragonal (fct) η-phase manganese nitride films have been grown on magnesium oxide (001) substrates by molecular-beam epitaxy. For growth conditions described here, reflection high energy electron diffraction and neutron scattering show primarily two types of domains rotated by 90° to each other with th…
The optical studies of SiO2 mesoporous materials with hierarchical tubules-within-tubule structure have been investigated by photoluminescence and Fourier-transform infrared transmittance (FTIR). Our results suggest that the radiative intensity can be strongly enhanced by annealing the samples in N2 environment. From…
We present theoretical evidence that the paramagnetic ${E}^{\ensuremath{'}}$ defect centers in amorphous silicon dioxide ( $a\ensuremath{-}{\mathrm{SiO}}_{2}$) do not have the same microscopic structures as those well-defined in the corresponding crystalline counterparts such as $\ensuremath{\alpha}\ensuremath{-}\math…
Truly stable metastable states are an artifact of the mean-field approximation or the zero-temperature limit. If such appealing concepts in glass theory as configurational entropy are to have a meaning beyond these approximations, one needs to cast them in a form involving states with finite lifetimes. Starting from e…
Thin-film Y3−xAl5O12:Tbx3+ (YAG:Tb) phosphor derived from a sol-gel chemistry is analyzed by x-ray diffraction, scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL). The metal alkoxides organic precursors were chosen as the starting materials to form the sol-gel. This liquid sol-gel was sp…
Low-resistance and nonalloyed ohmic contacts to epitaxially grown n-ZnO were formed by exposing n-ZnO to an inductively coupled hydrogen and an argon plasma. Using Ti/Au, the specific contact resistivity of the ohmic contact was drastically decreased from 7.3×10−3 to 4.3×10−5 Ω cm2 by hydrogen plasma treatment. The ph…
The low-temperature magnetic and transport properties of La2/3Sr1/3MnO3 nanoparticles have been investigated. It is found that a surface spin-glass behavior exists in La2/3Sr1/3MnO3 nanoparticles, which undergo a magnetic transition to a frozen state below 45 K. The low-temperature surface spin-glass behavior exists e…
Commercial systems for precise placement of pre-preg composite tows are enabling technology that allows fabrication of advanced composite structures in which the tows may be precisely laid down along curvilinear paths within a given ply. For laminates with curvilinear tow paths, the fiber orientation angle varies cont…
Portnoi and Galbraith recently proposed a beautiful and intriguing relationship defining the critical screening lengths associated with the apparition of new bound states for the two-dimensional statically screened Coulomb potential. Not only does semiclassical quantum theory show that this relationship is unfortunate…
The origin of ferromagnetism in semimagnetic III-V materials is discussed. The indirect exchange interaction caused by virtual electron excitations from magnetic impurity acceptor levels to the valence band can explain ferromagnetism in GaAs(Mn) in both degenerate and nondegenerate samples. Formation of ferromagnetic…
Recent experiments show that supercooled liquids around the glass transition temperature are ``dynamically heterogeneous'' [H. Sillescu, J. Non-Cryst. Solids 243, 81 (1999)]. Such heterogeneity is expected from the random first order transition theory of the glass transition. Using a microscopic approach based on this…
A phase-field model for predicting the coherent microstructure evolution in constrained thin films is developed. It employs an analytical elastic solution derived for a constrained film with arbitrary eigenstrain distributions. The domain structure evolution during a cubic→tetragonal proper ferroelectric phase transit…
Andreev reflection at a $\mathrm{Pb}/{\mathrm{CrO}}_{2}$ point contact has been used to determine the spin polarization of single-crystal ${\mathrm{CrO}}_{2}$ films made by chemical vapor deposition. The spin polarization is found to be $0.96\ifmmode\pm\else\textpm\fi{}0.01$, which confirms that ${\mathrm{CrO}}_{2}$ i…
Interaction of TM-polarized waves with a subwavelength thick metallic slit has been analyzed. A Fabry-Pérot-like behavior is reported. The resonance peaks, however, have very low magnitude and a systematic shift towards longer wavelengths is observed. The slit being narrow, this shift can be interpreted as the result…
Combinatorial laser molecular-beam epitaxy method was employed to fabricate epitaxial ZnO thin films doped with all the 3d transition metal (TM) ions in a high throughput fashion. The solubility behavior of TM ions was discussed from the viewpoints of the ionic radius and valence state. The magneto-optical responses c…
The effect of an imposed shear flow on the stability of directionally solidifying binary alloys is investigated. It is shown that without the imposed shear flow the system is dominated by stationary boundary-layer-mode convection, a convection of salt-finger type confined to the solute boundary layer above the melt/mu…
Convective flow of molten gallium is studied in a small-aspect-ratio rectangular, differentially heated enclosure. The three-dimensional nature of the steady flow is clearly demonstrated by quantitative comparison between experimental temperature measurements, which give an indication of the strength of the convective…
We have carried out a detailed study of the chemical bonding for two room-temperature stable platinum silicide phases, tetragonal alpha-Pt_2Si and orthorhombic PtSi. An analysis of the valence electronic charge density reveals surprising evidence of covalent three-center bonds in both silicide phases, as well as two-d…