Interlayer Disorder Research Articles

Exciton polaritons and their one-dimensional localization in disordered quantum-well structures

A theory of the Anderson localization of light in randomly arranged ultrathin layers (quantum wells) uniform in lateral dimensions and possessing intrinsic optical resonances is put forward. To solve the multiple-scattering problem, a model of layers with a δ-function resonance dielectric polarization is proposed. The model is an electromagnetic counterpart of the electronic model of zero-radius potentials. Interlayer disorder is included under the assumption of a low average concentration of identical layers in order to calculate analytically the one-and two-photon characteristics of electromagnetic-radiation transport, in particular, the average energy density and the Anderson localization length of light. The analysis is carried out for a structure with randomly distributed quantum wells in which quasi-two-dimensional excitons of different quantum wells are in resonance while their wave functions do not overlap. It is shown that the average electromagnetic field propagates through this disordered structure in the form of polaritons but are produced in exciton reemission between quantum wells. The localization length of light in the polariton spectral region decreases substantially, because the scattering (reflection) of light by individual quantum wells grows near the excitonic resonance.

Localization transition in multilayered disordered systems

The Anderson delocalization-localization transition is studied in multilayered systems with randomly placed interlayer bonds of density $p$ and strength $t$. In the absence of diagonal disorder (W=0), following an appropriate perturbation expansion, we estimate the mean free paths in the main directions and verify by scaling of the conductance that the states remain extended for any finite $p$, despite the interlayer disorder. In the presence of additional diagonal disorder ($W > 0$) we obtain an Anderson transition with critical disorder $W_c$ and localization length exponent $\nu$ independently of the direction. The critical conductance distribution $P_{c}(g)$ varies, however, for the parallel and the perpendicular directions. The results are discussed in connection to disordered anisotropic materials.

ChemInform Abstract: Synthesis and Characterization of the Layered Vanadium Borophosphate (Imidazolium)3.8(H3O)1.2 [(VO)4(BO)2(PO4)5] ×0.3H2O.

The first layered vanadium borophosphate (imidazolium)3.8(H3O)1.2[(VO)4(BO)2(PO4)5].0.3H2O (1) has been synthesized hydrothermally and characterized by chemical analysis, infrared and Raman spectroscopy, and thermogravimetric and magnetic measurements. The compound crystallizes in the monoclinic space group C2/c, a = 9.4737 (5) A, b = 22.1444 (12) A, c = 17.2192 (13) A, beta = 105.936 (1) degrees, Z = 4. The structure contains a novel borophosphate secondary building unit, [B2P5O22], in which two BP2O10 trimers are linked by an additional PO4 tetrahedron. These units are connected by V(IV)2O8 dimers and V(IV)O5 square pyramids to form layers. The space between the layers is filled by disordered imidazolium and hydronium cations and water molecules that form a complex network of hydrogen bonds. A model for the interlayer disorder is proposed.

Synthesis and characterization of the layered vanadium borophosphate (imidazolium)3.8(H3O)1.2[(VO)4(BO)2(PO4)5].0.3H2O.

The first layered vanadium borophosphate (imidazolium)3.8(H3O)1.2[(VO)4(BO)2(PO4)5].0.3H2O (1) has been synthesized hydrothermally and characterized by chemical analysis, infrared and Raman spectroscopy, and thermogravimetric and magnetic measurements. The compound crystallizes in the monoclinic space group C2/c, a = 9.4737 (5) A, b = 22.1444 (12) A, c = 17.2192 (13) A, beta = 105.936 (1) degrees, Z = 4. The structure contains a novel borophosphate secondary building unit, [B2P5O22], in which two BP2O10 trimers are linked by an additional PO4 tetrahedron. These units are connected by V(IV)2O8 dimers and V(IV)O5 square pyramids to form layers. The space between the layers is filled by disordered imidazolium and hydronium cations and water molecules that form a complex network of hydrogen bonds. A model for the interlayer disorder is proposed.

Pseudogap effects on the c-axis charge dynamics in copper oxide materials

The c-axis charge dynamics of copper oxide materials in the underdoped and optimally doped regimes has been studied by considering the incoherent interlayer hopping. It is shown that the c-axis charge dynamics for the chain copper oxide materials is mainly governed by the scattering from the in-plane fluctuation, and the c-axis charge dynamics for the no-chain copper oxide materials is dominated by the scattering from the in-plane fluctuation incorporating with the interlayer disorder, which would be suppressed when the holon pseudogap opens at low temperatures and lower doping levels, leading to the crossovers to the semiconducting-like range in the c-axis resistivity and the temperature linear to the nonlinear range in the in-plane resistivity.

Structural Order/Disorder in the AlSr2YCu2O7Compound

From X-ray diffraction (XRD) data, AlSr2YCu2O7phase shows a tetragonal unit cell and space groupP4/mmm, with lattice parametersa=b=3.862(5) Å andc=11.095(5) Å. From selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) studies, a super structure with related parametersas=2at,bs=4at, andcs=2ctwas found, which is considered to be due to the existence of two types of symmetry-related zigzag AlO4chains along thea-direction. Simultaneously, some interlayer disordering occurs, which can be due to the disordered arrangement of these two AlO4chains along thec-axis.

Order/disorder of tetrahedral-chains in AlSr 2YCu 2O y and related oxide superconductors examined by HRTEM

Order-disorder structures in AlSr 2YCu 2O 7 (Al-1212), related to characteristic arrangements of AlO 4 tetrahedral chains, are examined by high-resolution transmission electron microscopy (HRTEM). Symmetry-related chains ( R- and L-) form intralayer ordering within each a-b plane, together with interlayer disordering along the c-direction. It is considered that the crystal has a micro-domain structure with two kinds of superstructures with c s=4c 0 and c s=2c 0

Structural Disorders in the Superconducting GaSr2Ca3Cu4Oy

Selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM) studies were performed on the new superconductor GaSr2Ca3Cu4Oy(Ga-1234),n= 4 member of the homologous series GaSr2Can−1CunO2n+3prepared under high pressure. Although it consists of rather irregular intergrowths of the blocks withn= 3, 4, and 5 [CuO2] layers, the average number of [CuO2] layers is close to 4. In addition, an intralayer ordering between two different types of [GaO4] tetrahedral chains along thebaxis, as well as an interlayer disordering of the chains along thecaxis, are also observed.

Microstructural characterization of GaSr 2Ca 2Cu 3O 9+δ, n = 3 member of the homologous series of superconductors GaSr 2Ca n−1 Cu nO 2 n+3

The microstructure of the n = 3 member of the homologous series of superconductors GaSr 2Ca n−1 Cu n O 2 n+3 prepared under high pressure (6 GPa) was investigated by means of selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The GaSr 2Ca 2Cu 3O 9+δ phase has an orthorhombic structure with a double periodicity along the b-axis, due to the intralayer ordering between two different types of GaO 4 chains. Also, interlayer disordering of the chains along the c-axis was observed.

Dose effects in Si FIB-mixing of short period AlGaAs/GaAs superlattices

ABSTRACTResults are presented on FIB mixing of an Al0.3Ga0.7As/GaAs superlattice with equal 3.5 nm barrier and well widths. Si++ was accelerated to 100 kV and implanted parallel to sample normal at doses ranging from 1013 to 1015/cm2. The level of inter-layer disordering was measured primarily by Auger depth profiling. The mixing effect of RTA-only increased roughly linearly with annealing time at both 950 and 1000°C, with the latter exhibiting a sharper slope. At either temperature, 90 s was sufficient to produce complete mixing within the accuracy of the measurement. An anneal of 10 s at 950°C, which was utilized in subsequent post-implantation annealing, resulted in ∼ 25% thermally-induced mixing, with a corresponding PL “blue shift” of 6 meV. The level of mixing by an ion dose of 1 × 1014/cm2 yielded a mixing parameter of 0.87, where 1.0 represents complete mixing. This is the lowest ion beam dose necessary for nearly complete mixing reported to date for either FIB or BB implantation. Doubling the dose to 2 × 1014/cm2 results in an increase in mixing by only 0.05 to 0.92. Larger doses produced a diminishing increase in mixing parameter.

Phase Transformation of Iron Vanadium Sulfides at High Temperatures

Abstract The phase relations of iron vanadium sulfides with the atomic Fe: V ratios 3 : 2 and 71 : 29 were examined by the high-temperature DTA and X-ray measurements. It was found that the structure of iron vanadium sulfide changes gradually from a less symmetric form to a highly symmetric form with the increase in temperature. Two types of phase transformations by vacancy order-disorder were observed at temperatures above 800 °C. One was due to the intralayer disordering of metal vacancies: V3S4-type→Cd(OH)2-type (type Ia) or V3S4-type+NiAs-type→Cd(OH)2-type (type Ib) at T1. The other was due to the entirely interlayer disordering of metal vacancies: Cd(OH)2-type→NiAs-type (type II) at T2 (T2>T1). The tentative phase diagram of iron vanadium sulfides with the atomic Fe: V ratio 3 : 2 was constructed on the basis of the DTA results.