Structure and magnetic property of (Ga,Cr)As films with different Cr contents

We report variations in structure and magnetic property of (Ga,Cr) As films with increasing Cr content x. Due to phase segregation, a tendency towards inhomogeneous distribution with increasing x is confirmed. Barkhausen-like magnetization and large remanent magnetic moment were also clearly observed in the samples with x<5.3%. However, spin-glass-like behaviors were observed in both dc and ac magnetic measurements, which might originate from the competition between magnetic nucleation and frustration of long ferromagnetic order in this inhomogeneous system. All the samples exhibit characteristics of variable-range hopping conductivity at temperature below 150 K. Typical magnetic circular dichroism structure was observed in the sample with x=7.9%.

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. (C) 2004 Elsevier B.V. All rights reserved.

The effect of a combined InAlAs and GaAs strained buffer layer on the structure and optical property of InAs quantum dots

The character of InAs quantum dots (QD) directly deposited on a combined InAlAs-GaAs (XML) strained buffer layer (SBL) has been investigated. This growth technique realizes high-density QD (5.88 x 10(10) cm(-2)) by changing the thickness of GaAs in InAlAs-GaAs SBL. The dependence of the density and the aspect ratio of QD on the GaAs thickness has been discussed in detail. The photoluminescence (PL) measurements demonstrate an obvious redshift with the increase of GaAs thickness. In addition, the deposition of InAs QDs grown on the combined InAlAs-GaAs SBL has an important effect of the QD properties. The ordered QD array can be observed from the sample deposited by atomic layer epitaxy, of which the PL peak shows an obvious redshift in comparison to the molecular beam epitaxy (MBE) QDs when the GaAs thicknesses are equal. (c) 2004 Elsevier B.V. All rights reserved.

Magnetic property and interface structure of Ta/NiO/NiFe/Ta

Ta/NiO/NiFe/Ta multilayers, utilizing Ta as buffer layer, were prepared by rf reactive and de magnetron sputtering. The exchange coupling field between NiO and NiFe reached a maximum value of 9.6x10(3) A/m at a NiO film thickness of 50 nm. The composition and chemical states at interface region of Ta/NiO/Ta were studied by using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there is an "intermixing layer" at the Ta/NiO land NiO/Ta) interface due to a thermodynamically favorable reaction 2Ta + 5NiO = 5Ni + Ta2O5. This interface reaction has a great effect on exchange coupling. The thickness of Ni+NiO estimated by XPS depth. profiles is about 8-10 nm.

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot. (C) 2004 Elsevier B.V. All rights reserved.

Microemulsion-mediated solvothermal synthesis and photoluminescent property of 3D flowerlike MnWO4 micro/nanocomposite structure

Novel three-dimensional (3D) flowerlike MnWO4 micro/nanocomposite structure has been successfully synthesized for the first time. The synthesized products were systematically studied by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) and photoluminescence (PL) spectra. It is found that both reaction time and temperature have significant effects on the morphology of the products.

Synthesis, structure and electrochemical property of calixarene potassium polyoxometalates

One inorganic-organic hybrid and two host-guest complexes were synthesized from calix[4] arene tetra acetic ether derivative( C60H80O12, L) and potassium polyoxometalates. The structures of the complexes were characterized with the elemental analysis, IR, TG-DTA and X-crystallographic. X-ray crystallographic studies reveal the formation of an ionic crystal, which contains a calix-cluster and calix-cluster-calix line array, and belongs to a typical inorganic-organic hybrid ( complex 1) or has a host-guest structure ( complex 2 and 3). The results of cyclic voltammograms at different scanning rates showed that the anode peak current of complex 1 was proportional to the square root of the scanning rate and the charge transfer process was controlled by pervasion. The anode peak current of complexes 2 and 3 was proportional to the scanning rate and the charge transfer process was controlled by the surface. The results suggest that there are consanguineous relationship between the anode reaction and the structure.

Synthesis, crystal structure, and thermal property of a novel supramolecular assembly: (NH42810424)(CHNO) O-[H(V)O(]2H)4(10)28(2), constructed from decavanadate and caffeine

A novel 3D supramolecular assembly constructed from decavanadate and caffeine building blocks, (NH4)(2)(C8H10N4O2)(4)[H4V10O28].2H(2)O (1), has been synthesized in aqueous solution and characterized by elemental analysis, IR, H-1 NMR, V-51 NMR, TG-DTA, and single crystal X-Ray diffraction. The compound 1 crystallizes in monoclinic system, space group P2(1)/n, a = 15.801(1) Angstrom, b = 12.914(1) Angstrom, c = 15.913(2) Angstrom, beta = 113.55degrees, V = 2976.4 (5) Angstrom(3), Z = 2, R = 0.0498 with 6818 reflections. Water molecules, ammonium ions, and caffeine act as "cement" linking the polyanions into 1D chain along the c-axis by hydrogen bonding. In compound 1, extensive hydrogen-bond contacts and strong pi-pi interactions lead to an ordered 3D supramolecular framework. TG-DTA curves indicate that the weight loss of the complex can be divided into three stages.

Synthesis, crystal structure, and photoluminescent property of a novel heterobimetallic Zn(II)-Ag(I) cyano-bridged coordination polymer incorporating,a pentameric unit [Ag(CN)(2-)](5) assembled by argentophilic interaction

A new photoluminescent heterobimetallic Zn(II)-Ag(I) cyano-bridged coordination polymer, [Ag5Zn2(tren)(2)(CN)(9)] (tren = tris(2-aminoethyl)amine) (1), has been synthesized and structurally characterized. It features rare linear pentameric unit of dicyanoargentate(I) ions assembled by d(10)-d(10) interaction as building blocks. Solid state emission spectrum of I shows strong ultraviolet luminescence with emission peak in the range of 376 nm.

Synthesis, characterization, crystal structure and magnetic property of asymmetrical double Schiff base heterotrinuclear complex: Cu(II)-Co(II)-Cu(II)

An asymmetrical double Schiff-base Cu(II) mononuclear complex, HCuLp (H(3)Lp is N-3-carboxylsalicylidene-N'-5-chlorosalicylaldehyde-1,3-diaminopropane) and a heterometal trinuclear complex with double molecular structure (CuLp)(2)Co center dot 5H(2)O have been synthesized and characterized by means of elemental analyses, IR and electronic spectra. The crystal structure of the heterotrinucler complex was determined by X-ray analysis. Each asymmetric unit within the unit cell of the complex contains two heterotrinuclear neutral molecules (a) [CuLpCoCuLp], (b) [(CuLpH(2)O) CoCuLp] and four uncoordinated water molecules. In the two neutral molecules, the central Co2+ ions are located at the site of O-6 with a distorted octahedral geometry, one terminal Cu2+ ion (Cu(3)) at the square-pyramidal environment of N2O3, and the other three at the square planar coordination geometry with N2O2 donor atoms. Magnetic properties of the heterotrinucler complex have been determined in the temperature range 5-300 K, indicating that the interaction between the central Co2+ ion and the outer Co2+ ions is antiferromagnetic.

Selection for variables in quantitative structure-activity/property relationship studies - Comparison between methods of orthogonal descriptors and leaps-and-bounds regression analysis

In this paper, the comparison of orthogonal descriptors and Leaps-and-Bounds regression analysis is performed. The results obtained by using orthogonal descriptors are better than that obtained by using Leaps-and-Bounds regression for the data set of nitrobenzenes used in this study. Leaps-and-Bounds regression can be used effectively for selection of variables in quantitative structure-activity/property relationship(QSAR/QSPR) studies. Consequently, orthogonalisation of descriptors is also a good method for variable selection for studies on QSAR/QSPR.

Morphology, structure, and rheological property of linear low-density polyethylene grafted with acrylic acid

The chain structure, spherulite morphology, and theological property of LL-DPE-g-AA were studied by using electronspray mass spectroscopy, C-13-NMR, and rheometer. Experimental evidence proved that AA monomers grafted onto the LLDPE backbone formed multiunit AA branch chains. It was found that AA branch chains could hinder movement of the LLDPE main chain during crystallization. Spherulites of LLDPE became more anomalous because of the presence of AA branch chains. Rheological behavior showed that AA branch chains could act as an inner plasticizer at the temperature range of 170-200 degreesC, which made LLDPE-g-AA easy to further process. (C) 2001 John Wiley & Sons, Inc.