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In the 1998-99 flight, BOOMERanG has produced maps of ∼4% of the sky at high Galactic latitudes, at frequencies of 90, 150, 240 and 410 GHz, with resolution ≳ 10'. The faint structure of the Cosmic Microwave Background at horizon and sub-horizon scales is evident in these maps. These maps compare well to the maps recently obtained at lower frequencies by the WMAP experiment. Here we compare the amplitude and morphology of the structures observed in the two sets of maps. We also outline the polarization sensitive version of BOOMERanG, which was flown early this year to measure the linear polarization of the microwave sky at 150, 240 and 350 GHz.
The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.
We show how estimates of parameters characterizing inflation-based theories of structure formation localized over the past year when large scale structure (LSS) information from galaxy and cluster surveys was combined with the rapidly developing cosmic microwave background (CMB) data, especially from the recent Boomerang and Maxima balloon experiments. All current CMB data plus a relatively weak prior probability on the Hubble constant, age and LSS points to little mean curvature (Ωtot = 1.08±0.06) and nearly scale invariant initial fluctuations (ns = 1.03±0.08), both predictions of (non-baroque) inflation theory. We emphasize the role that degeneracy among parameters in the Lpk = 212 ± 7 position of the (first acoustic) peak plays in defining the Ωtot range upon marginalization over other variables. Though the CDM density is in the expected range (Ωcdmh2 = 0.17 ± 0.02), the baryon density Ωbh2 = 0.030 ± 0.005 is somewhat above the independent 0.019 ± 0.002 nucleosynthesis estimates. CMB+LSS gives independent evidence for dark energy (ΩΛ = 0.66 ± 0.06) at the same level as from supernova (SN1) observations, with a phenomenological quintessence equation of state limited by SN1+CMB+LSS to wQ < −0.7 cf. the wQ=−1 cosmological constant case.
BOOMERanG has recently resolved structures on the last scattering surface at redshift ˜ 1100 with high signal to noise ratio. We review the technical advances which made this possible, and we focus on the current results for maps and power spectra, with special attention to the determination of the total mass-energy density in the Universe and of other cosmological parameters.
We present four wave mixing experiments on GaN. We find an intrinsic homogeneous broadening of the A-exciton of 1.67 meV. A pronounced beating with a period of 0.52 ps is observed at excitation energies between the A- and the B-exciton and corresponds to an energy splitting of 7.98 meV of A- and B-exciton.
Epitaxial layers of GaN on c-plane sapphire are analyzed by continuous-wave and time-resolved photoluminescence at 4K and by X-ray diffraction. Besides the well-known emissions from hexagonal GaN we observe luminescence bands at 3.279 and 3.15 to 3.21 eV which are identified as the transition of the donor bound exciton and the donor-acceptor pair recombination in cubic GaN, respectively. Measurements of the luminescence decay times are essential for the clarification of the emission processes. Due to the probing depth of about 200 nm in PL we find that the fraction of cubic phase typically decreases with layer thickness. In our best samples, however, we do not detect the cubic phase at all.
Defects introduced into single crystals of Al,Cu, and Fe by low temperature fast neutron irradiation were examined by diffuse scattering of X-rays. Structure and correlations of interstitials and vacancies were investigated after irradiation and during annealing. The primary defect structure is characterized by the correlation of defects in defect cascades. Size distributions for the arrangement of interstitials and vacancies were obtained. The evolution of the damage structure during recovery was followed and found to depend on the primary damage state. In Al we find large and dilute cascades with a mean radius of R-90Å, whereas in Cu small and dense cascades with R-20Å are produced. During recovery in Cu dislocation loops of interstitial and vacancy type are formed. In Al agglomeration of interstitials does not lead to loop formation. In Fe rather dilute cascades with R=60Å are observed. Here only small agglomerates of interstitials evolve during recovery in stages I and III.
The x-ray diffuse scattering from a single crystal of Cu3Au was measured in absolute units in a volume of reciprocal space. The measurement was made while the crystal was held at 703 K (approximately 35 K above the critical temperature for ordering) and the measured intensity was separated into components due to short range order (SRO) and strain. The Warren short range order parameters, pair interaction potentials and the first and second order static atomic displacements were obtained by Fourier inversion of these separated intensities. The relative interatomic pair potentials, out to the third shell, were found to be V2/V 1=-0.5 and V3/V 10 consistent with earlier determinations. The first order atomic pair displacements were found to be contrary to what has previously been assumed: Au-Au first neighbor pairs were found to have negative displacements on average and AuCu pairs positive displacements, compared to the average interatomic distance.
Microchemical and microstructural characterization, using established SEM and STEM techniques, has shown that most (>90% of the area) of the Bi-Sr-Ca-Cu-O thin films prepared by reactive magnetron sputtering on both NaCl and MgO substrates in the (100) orientation is the superconducting phase Bi2 Sr2 CaCu2 O8 (2212); with largely defect free single crystal grains oriented with the a-b conduction planes parallel to the substrate. The geometrical interconnectivity is high and the grain boundaries are clean and well ordered without any intermediate layers to limit the superconductivity. There were also small patches (>10%) in which the Bi- and Cu-rich phases, Bi2 SrCuO5 and CuO, had separated. The films had an onset Tc at 115K with zero resistance at 85K and a Jc of 105A/cm2 at liquid He temperature.
We present the results of Rietveld analysis on the neutron diffraction intensities of Er2Fe17, which crystallizes in the hexagonal Th2Ni17 phase. Of the reflection sets, h-k ≠ 3n, l = 2n+1 and l = 2n, the former fit better than the latter and are in general more intense. This suggests disordered transition-metal-substitution on the planes parallel to the c-axis resulting in stacking faults; ABABs... is the usual sequence of ordered transition-metalsubstitutions in the parent CaCu5 phase. Influence of such deformations on the interatomic distances inthe substitution zone and the consequent magnetic bonding and anisotropy is discussed.
In this investigation, we report on detailed microstructural characteristics of LPCVD WSi 2 films deposited on doped/undoped polysilicon and subjected to boron and phosphorus implantation and implant activation at temperatures up to 1100° C. The polysilicon films were doped with phosphorus using a POC13 source to obtain a sheet resistance of ∼ 25 Ω/ and the films were coated with about 300nm of Si rich (Si:W atomic ratio 2.6) LPCVD WSi2. The microstructures of as-deposited and high temperature annealed polycide films were studied in detail using TEM. The electrical sheet resistances were measured using four-point probes. The initial polysilicon doping level, silicide annealing conditions, subsequent implant into the polycide, and implant activation all had profound effects on the microstructural characteristics of both the silicide and polysilicon.
The microstructural and compositional changes produced in the near surface region of single crystals of α-A12O3 by ion-implantation with iron have been investigated by a number of complementary techniques, including Rutherford backscattering spectroscopy (RBS), conversion-electron Mdssbauer spectroscopy (CEMS), analytical electron microscopy (AEM), and scanning transmission electron microscopy (STEM). Iron precipitates, 1 to 3 nm in diameter, have been identified in as-implanted material at depths corresponding to the peak in the deposited iron concentration profile. The same techniques have been used to monitor the redistribution of iron and the corresponding changes in valence state during post-implantation annealing. Electron microscopy has been used to correlate RSB and CEMS results with the microstructural development.
We present high resolution transmission electron microscopy results of Pbl-xEuxTe alloys that show evidence for a compositional instability for x ≈ 0.5 when the alloys are grown on BaF2 substrates. The Pbl-xEuxTe solid solution becomes stable at room temperature if a buffer layer of PbTe is grown on the BaF2 substrate prior to thegrowth of the Pb1-xEuxTe layer. The stabilization ofthe Pb1-xEuxTe solid solution is the result of the additional energy term due to the strain between the Pbl-xEuxTe film and the PbTe buffer layer. The estimated critical temperatures for decomposition of the Pb1-xEuxTe alloys with and without the PbTe buffer layer are ≈0 K and.≈ 366 K, respectively in accord with our1 experimental observations. We also present models for the structure of the decomposed phaseand use them to obtain simulated images using computing methods. The simulated images are compared with those obtained experimentally.
A Transmission Electron Microscopy study of the defect microstructure in Silicon On Sapphire before and after Rapid Thermal Annealing is presented. The annealed material is shown to contain a much lower density of twins and threading dislocations. Comparison with the asgrown microstructure enables possible explanations to be proposed for these observations in terms of the removal of barriers to the introduction and movement of dislocations in response to misfit and thermal expansion strains. A regular array of misfit dislocations is observed in the interface of annealed material. These have non-rational line directions and are consistent with complete misfit accommodation.
The influence of Cu or Pd contamination on the integrity of thin SiO2 layers was studied on (100) and (111) Si substrates. Wafers were contaminated intentionally on their backsides and indiffusion of the impurities was carried out at 1200° C or 900°C by rapid thermal annealing. Both, electrical tests and cross-sectional transmission electron microscopy were applied to investigate the failure mechanisms of the oxide. Curich silicide particles as well as Pd-Si precipitates were observed at the SiO2 interface. They result in cracking and bending of the oxide film or reducing the oxide thickness. These oxide failures could be explained by a precipitation process which is associated with the emission of Si self-interstitials.
X-ray diffraction line profiles have been described in an earlier work published by the authors as a convolution of three functions: particle size broadening, and two types of non-uniform strain broadening. The strain coefficients used in this approach are simply related to the strain coefficients obtained by Krivoglaz et.al, using a theory based upon correlated dislocations. This connection enables us to determine the dislocation density and the ratio of the correlation range to the mean particle size. Results for cold worked fcc and bcc materials as well as highly imperfect sputtered films of Mo are considered. Dislocations are highly correlated in cold worked metals, whereas correlation is much lower in sputtered films deposited at low temperatures. In each case, the dislocation density is high. An analysis of wear debris consisting of cubic Zirconia gave the highest dislocation density and correlation. The close similarity between the early work on cold work filings and wear debris provides insights on wear mechanisms.
High spatial resolution characterization of quantum wells has been performed by monochromatic cathodoluminescence imaging and by large angle convergent beam electron diffraction. The satellite lines to sublattice reflections which have been interpreted previously in terms of kinematical diffraction theory are here explored in detail by dynamical diffraction theory.
A laser method for non-destructively mapping the distribution of aluminum-hole centers, Al-h, in quartz has been developed utilizing an aluminum-hole A3 absorption band nearly coincident with the He-Ne 632.8 nm wavelength. Al-h distribution for quartz sample with varying aluminum concentration compared with coloration and the dose dependence of competing aluminum compensation mechanisms Al-h and Al-OH is determined. From a comparison with electron spin resonance(ESR) results an approximate absorption coefficientcalibration of 0.1 cm-1/ppm Al-h is found.
The geometric and electronic structure of metal adsorbates on cleaved GaAs(l10) surfaces is studied with the scanning tunneling microscope. For the metals Sb and Bi, an ordered monolayer is formed, although in the case of Bi a series of misfit dislocations appear in the overlayer. In the case of Au, individual atoms are observed on the surface, forming clusters at higher metal coverage. Spectroscopic measurements reveal the presence of a state within the GaAs band gap. This state is observed near individual metal adsorbates (for Au and Sb), and near the edge of metal terraces (for Sb and Bi). The observed state is responsible for determining the position of the Fermi-level at the surface.