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Lattice-matched Al1−xInxN / GaN heterostructures with InN mole fraction (x) of 0.18 have attracted considerable interest for use in GaN-based optoelectronic devices. Because the light emission efficiency (η emission ) of Al1−xInxN alloys is far less than that of InxGa1−xN, understanding its causes is essential. For this purpose, room-temperature photoluminescence lifetime (τ PL RT ), which almost represents the nonradiative recombination lifetime that limits the internal quantum efficiency in low η emission semiconductors, of c-plane Al1−xInxN epilayers nearly and modestly lattice-matched to GaN (0.11 ≤ x ≤ 0.21) was examined. For the epilayers grown on low threading dislocation density (TDD) GaN substrates (≪ 10 7 c m − 2 ), τ PL RT principally decreased with increasing x, indicating a progressive increase in the concentration of nonradiative recombination centers (NRCs), N NRC . One of the probable causes is the growth temperature (T g ) reduction that is indispensable to incorporate more In, because in insufficient T g regime higher T g is preferred for enhancing the surface migration of adatoms to decrease the concentrations of vacancies that compose NRCs. The Al1−xInxN epilayers of the same x but grown on high TDD (> --> 10 8 c m − 2 ) GaN-on-sapphire templates exhibited shorter τ PL RT . Because the diffusion length of minority carriers was nearly zero in the Al1−xInxN epilayers, the shorter τ PL RT indicates higher bulk N NRC in high TDD epilayers. The Al1−xInxN epilayers of considerably rough surface morphologies exhibited spatially inhomogeneous τ PL RT , implying that excited carriers recombined everywhere at InN-rich to InN-poor portions, where N NRC were likely lower to higher, respectively, than the average due to the deviations in the surface stoichiometry at various non-c-plane surfaces at a given T g . [ABSTRACT FROM AUTHOR]

We have investigated the electronic structure of silver chalcogenides Ag2X (X = S, Se, Te) and their solid solutions using hard x-ray photoemission spectroscopy in combination with density functional theory calculations using generalized gradient approximation (GGA). By including the corrections for on-site Coulomb interactions (GGA + U), we successfully reproduced the valence band photoemission spectra, which consist mainly of the Ag 4d band, by calculation. The estimated values for U = 4–6 eV are slightly high for Ag 4d electrons but are consistent with those used in previously reported structural studies. On the other hand, the magnitude of the energy gap is virtually independent of U. These results suggest the strong correlation between Ag 4d electrons in Ag2X compounds to have surprisingly little impact on their electron transport properties. [ABSTRACT FROM AUTHOR]

We have investigated the electronic structure of a potential thermoelectric material, higher manganese silicide, and its solid solutions with supersaturated Re by means of hard x-ray photoemission spectroscopy. The unusual Re substitution dependence of thermoelectric properties in the higher manganese silicide, reducing the electrical resistivity without altering the Seebeck coefficient, can be explained in terms of the variation of the density of states at the Fermi level and its energy derivative. Such an electronic structure variation contributes to an improvement in the thermoelectric performance in combination with the suppressed thermal conductivity. [ABSTRACT FROM AUTHOR]

In0.12Ga0.88N/GaN multiple quantum wells were studied using optical spectroscopy.

Research was conducted to examine the possibility of application of transition metal oxides to transparent conductors. Electronic and optical spectroscopies were used to estimate the electronic structure of AMoO3 with perovskite structure. Results provide evidence of the possibility of application in transparent conductors for the ultraviolet region since no intense peaks were detected in the energy region between the two absorption bands.

Research was conducted to examine the pseudomorphic Ga(sub 1-x)In(sub x)N/GaN single heterostructures in the composition range 0

The microscopic structure and magnetic properties of Mn-Al multilayered films are investigated.Mn and Al layers are alternately deposited on an MgO(100) single-crystal substrate at a temperature of 300 degrees centigrade. The films' microstructureand magnetic properties are then measured using high-resolution transmission electron microscopy and vibrating sample magnetometry, respectively. Results show the presence of highly magnetic regions near the Mn-Al interfaces.

The magnetic properties of layered oxysulfide Sr2Cu2(Co,Cu)O2S2 with the (Co,Cu)O2 planes are examined. Long time decay is observed at 10 and 75 K and the divergence between zero-field cooled and field cooled magnetizations is observed below 80 K.

The temperature dependence of the magnetization reversal in a series of four TbFeCo films prepared under different sputtering pressures and with different underlayer properties is examined. The activation volumes for films increased with the increasing temperature and declined with the increase in sputtering pressure while the increase in argon sputtering resulted in a change in the magnetic anisotropy direction from perpendicular to in-plane.

A noninteraction particle model is used analyze the magnetic characteristics of single-crystal cobalt films aligned on the c-axis. These films, which exhibit a perpendicular magnetization component, reveal an in-plane anisotropy. The cobalt films are epitaxially grown on rigid underlayers.

Fabrication of a V3Si multifilamentary superconductor comprising a high overall Jc is possible through a process involving modified bronze. Overall Jc has 10 times the value of conventional V3Si wire values. The values are 1 times 10 to the 18th power A/square meter at 12.5 T and 1.3 times 10 to the 9th power A/square meter at 5T. Orthonucleic constants may also influence the Tm3+ ion, which is already influenced by a tetragonal crystal field.

The influence of layer thickness on the magnetic characteristics of Mn/Al multilayered structures was investigated to elucidate the relationships between magnetic properties and film structure. The results showed that the Mn lattice spacing vertical to the substrate decreased when the Mn layer thickness was increased or when the Al layer was decreased. Changes in the Mn lattice spacing controlled saturation magnetization and magnetic anisotropy.

We have studied the magnetic properties of layered oxysulfide Sr[sub 2]Cu[sub 2](Co,Cu)O[sub 2]S[sub 2] with the (Co,Cu)O[sub 2] planes. Magnetic susceptibility shows a broad maximum indicative of two-dimensional antiferromagnetic nature above 140 K. Below 80 K, the divergence between zero-field cooled and field cooled magnetizations is seen; long time decay is observed at 10 and 75 K, while it is not observed at 45 K. These feature is discussed from the viewpoint of the strongly and frustrated spin system which is different from the traditional spin glass. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the correlation between the structure and the magnetic properties of manganese-aluminum multilayered films. Experimental details; Results and discussion; Conclusions.

Deals with a study which investigated improvements in high-field superconducting performance of V[sub3]Ga by a two-stage reaction process. Preparation of the V[sub3]Ga specimens; Findings.

A silicide material with a good n-type thermoelectric property has been discovered. This silicide possesses a composition of Mn3-xCrxSi4Al2 (0 ≤ x ≤ 0.7) and hexagonal CrSi2 structure. The a- and c-cell parameters decrease with increasing the amount of Cr substitution. The absolute values of Seebeck coefficient and electrical resistivity increase by Cr substitution up to 573 K because of reduction of carrier density. The dimensionless thermoelectric figure of merit ZT reaches 0.21 at 773 K for a non Cr substituted sample at the Mn site and 0.30 at 573 K for a Cr substituted one with x = 0.3. Since oxide passive layer is formed around the surface, electrical resistivity measured at 873 K is constant for 2 days in air, which indicates good oxidation resistance in air of this material. The Mn3-xCrxSi4Al2 is a promising n-type material with a good oxidation resistance in the middle temperature range. A thermoelectric module consisting of 64 pairs of legs has been fabricated using MnSi1.7 and non Cr substituted Mn3Si4Al2 devices as p- and n-type legs, respectively. Output power reaches 9.4 W, which corresponds to 2.3 kW/m2 of power density against surface area of the substrate, for a heat source temperature of 873 K in air. [ABSTRACT FROM AUTHOR]

Discusses the reduction of cell size in hybrid bubble memory devices. Composition of the minor loops in hybrid devices; Problem posed by ion implantation in hybrid devices; Method for operating bias field adjustment.