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Mechanical strains and stresses are a major concern in the development of copper-based on-chip metallization. Synchrotron x-ray topography (SXRT), micro-Raman spectroscopy, finite element modeling (FEM), and atomic force microscopy (AFM) have been used to examine the strain fields imposed by electroless Cu metallization on the underlying Si. As expected, we have observed enhanced strain regions close to the metal line edges. These strain fields tend to zero at annealing temperatures approaching 200 °C, and thereafter the magnitudes of the strain fields at 300 °C and 400 °C are much higher, implying a return to a higher strain regime. Although the strain transition point is slightly different from the SXRT result, the FEM results confirm the existence of a zero-strain transition point as a function of thermal anneal. We have also examined the generated stress in Si as a function of Cu linewidth L. We have found that the stress σXX due to the electroless copper metallization is empirically related to the Cu linewidth in terms of an exponential distribution. For Cu linewidths less than 20 μm, the stress magnitudes increased with decreasing Cu linewidth due to the thermal stress in the absence of self-annealing, whereas the stress decreased with increasing linewidths in the range of 60–100 μm due to a relief of the thermal stress possibly via the self-annealing effect. This self-annealing phenomenon was observed using AFM. It is observed that the stresses in the Si shifted to a compressive state after annealing at 400 °C. [ABSTRACT FROM AUTHOR]

In this paper, low energy electron beam (5-20 keV, 0-500 μAs/cm2) induced damage on a GaN/InGaN/GaN near-surface quantum well structure is studied. Exposure to low energy electron beam is shown to significantly reduce the optical quality of the structure. It is also observed that reducing the electron beam energy causes larger PL intensity reduction. This can be explained by considering the beam penetration depth, which is shown to be smaller with lower e-beam energies. The damage is believed to be attributed to enhanced dislocation mobility upon low energy electron beam irradiation. However, further studies are needed to confirm the mechanism. These results should be taken into consideration in low energy electron beam related sample characterization and preparation. [ABSTRACT FROM AUTHOR]

Abstract: Volatile organic compounds (VOCs) emitted from vegetation to the atmosphere contribute to global climate change, but climate change factors also affect VOC emission from vegetation. Soil-grown Norway spruce seedlings were exposed to elevated ozone (1.4×ambient ozone concentration) and elevated temperature (ambient+1.3°C) alone and in combination as well as to ambient ozone and temperature treatments under open-field conditions. VOC emissions (mainly terpenoids), genes involved in early steps of plastidial monoterpene and isoprene synthesis, photosynthetic parameters and growth were measured. In July, when daytime elevated ozone concentrations had been over 40ppb, ozone doubled the total terpenoid emissions by increasing the emissions of many monoterpenes and sesquiterpenes. Elevated temperature changed the terpenoid profile by increasing the emissions of oxygenated monoterpenes, but did not influence total emissions. Terpenoid emission profiles also differed between elevated ozone alone and elevated ozone in combination with elevated temperature. In August, when daytime elevated ozone concentrations had been ca. 30ppb, significant treatment effects were not found. Ozone and temperature reduced the expression of DXS2B (1-deoxy-d-xylulose 5-phosphate synthase type II), and ozone that of DXR (1-deoxy-d-xylulose 5-phosphate reductoisomerase) in August. Elevated temperature reduced the stem diameter growth, net photosynthesis and stomatal conductance, but elevated ozone did not have effects on these parameters. Results suggest that elevated temperature may not modify the ozone responses, or vice versa, in terms of gas exchange, growth or total terpenoid emission rates of young Norway spruces in a near-future climate. However, observed changes in terpenoid emission profiles may be important in the future climate, as reactivity in the troposphere differs between individual terpenoids. [Copyright &y& Elsevier]

This paper examines the utilization of plasma-enhanced atomic layer deposition grown AlN in the fabrication of a high-k insulator layer on GaAs. It is shown that high-k GaAs MIS capacitors with an unpinned Fermi level can be fabricated utilizing a thin ex-situ deposited AlN passivation layer. The illumination and temperature induced changes in the inversion side capacitance, and the maximum band bending of 1.2 eV indicates that the MIS capacitor reaches inversion. Removal of surface oxide is not required in contrast to many common ex-situ approaches. [ABSTRACT FROM AUTHOR]

We have developed a gas-phase nanoparticle generator that produces stable and well-defined size distributions for TiO2. The online analyses of the gas-phase compounds and total number concentration of the generated particles as well as the off-line analysis of the filter samples confirmed the stability of the production. The major advantage of this reactor is that the test substance is directly in the aerosol phase, and thus no preprocessing is needed. This eliminates the physicochemical changes between bulk and administrated material during storing or processing. This system is easy to adjust to different experimental setups and precursors. As a result, wellcharacterized nanomaterials for inhalation exposure studies can be produced. At mass concentration of 30 mg/Nm³, the count mean diameter was 126 nm (geometric SD 1.6), mass mean diameter was 161 nm (2.0), mass median aerodynamic diameter was 125 nm, and the concentrations of harmful gas-phase by-products remained low. The produced powder consisted of crystals of anatase (77 vol%) and brookite (23 vol%), and its specific surface area was 69 m²/g. [ABSTRACT FROM AUTHOR]

Abstract: Ultrathin gallium nitride passivation layers grown in situ on near-surface quantum wells using metalorganic vapour-phase epitaxy (MOVPE) with dimethylhydrazine as nitrogen source are reported. Nitridation of GaAs using DMHy during the post-growth cool-down is also studied. The effect of passivation on the surface recombination rate of quantum well (QW) structures is characterized using low-temperature (10K) photoluminescence. Measured after growth, the GaN passivation is shown to enhance the PL intensity of the near-surface QWs approximately by a factor of 20. For samples stored in ambient air for 5 months, the enhancement is nearly . The results suggest that MOVPE-grown thin GaN layers are applicable to GaAs surface passivation. [Copyright &y& Elsevier]

Abstract: Superlattices of cubic gallium nitride (GaN) and gallium arsenide (GaAs) were grown on GaAs(100) substrates using metalorganic vapor phase epitaxy (MOVPE) with dimethylhydrazine (DMHy) as nitrogen source. Structures grown at low temperatures with varying layer thicknesses were characterized using high resolution X-ray diffraction and atomic force microscopy. Several growth modes of GaAs on GaN were observed: step-edge, layer-by-layer 2D, and 3D island growth. A two-temperature growth process was found to yield good crystal quality and atomically flat surfaces. The results suggest that MOVPE-grown thin GaN layers may be applicable to novel GaAs heterostructure devices. [Copyright &y& Elsevier]

Single strain-induced quantum dots are isolated for optical experiments by selective removal of the inducing InP islands from the sample surface. Unpolarized emission of single exciton, biexciton, and triexciton transitions are identified by power-dependent photoluminescence spectroscopy. Employing time-resolved experiments performed at different excitation powers, we find a pronounced shift of the rise and decay times of these different transitions as expected from cascaded single photon emissions. Good agreement is found for a rate equation model for a three step cascade. [ABSTRACT FROM AUTHOR]

The optical properties of the in situ epitaxial GaN and InP passivated InGaAs/GaAs near-surface quantum wells, which were fabricated by metal organic vapor phase epitaxy, are investigated. Low-temperature photoluminescence (PL), time-resolved photoluminescence, and photoreflectance are used to study the passivation effect. Both GaN and InP passivations are observed to significantly enhance the PL intensity and carrier lifetime and to reduce the surface electrical fields. Comparison of the methods shows that the epitaxial InP passivation is more effective. However, epitaxial GaN and nitridation methods are comparable with InP passivation. [ABSTRACT FROM AUTHOR]