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The binding of various donor-acceptor pairs and acceptor-acceptor pairs and the resulting impact on the maximum charge carrier density are examined. For both donor-acceptor and acceptor-acceptor codoping, the binding is expected to lead to a reduced diffusion and a more abrupt junction formation.

A prism coupler is used for examining the polarization-dependent optical properties of slab waveguide films, which are composed on nanoparticles dispersed in a Si[O.sub.2] matrix. The optical spectra of the nanocomposite films are compared with those of cosputtered films and the optical anisotropy of the films are modeled and analyzed based on an effective medium theory with Maxwell-Garnett geometry and layer-by-layer photonic band-gap structures.

The effect of copper precipitation on the formation of denuded zone (DZ) in Czochralski silicon is examined by using scanning infrared microscopy (SIRM) and optical microscopy. The formation of DZ is affected by the copper precipitation mechanism, which is controlled by the annealing temperature and point defects.

The small signal gain measurements of optically excited terahertz Si:P and Si:Bi lasers are presented. It is found that the silicon lasers are optically excited with radiation from a free electron laser or a C[O.sub.2] laser.

The densities and viscosities of silicate melts depend strongly on pressure, in part because of potentially measurable structural rearrangements. In an attempt to further understand these changes and how they affect macroscopic properties, we have used [sup.27]Al MAS NMR to determine the coordination of the Al cations in a series of aluminosilicate glasses quenched from melts at pressures of 2 to 8 GPa, have measured the glass densities, and have applied an in-situ falling sphere method to measure melt viscosities at high pressure. Spectra from these four- and five-component glasses show increasing Al coordination with increasing pressure and with increasing average field strength of the modifier cation, as was previously reported for simpler compositions. These data also indicate that when multiple modifier cations are present (e.g., Ca and K), the Al coordination is lower than what would be expected from linear combinations of the appropriate aluminosilicate end-members. The viscosity of [Ca.sub.3][Al.sub.2][Si.sub.6][O.sub.18] melts, measured using a falling sphere method that combines multianvil techniques with synchrotron X-ray radiography, may reach a minimum at a pressure below 6 GPa. A quasi-thermodynamic approach using equilibrium constants for the reactions that generate high-coordinated Al suggests that this pressure may be related to a maximum in the concentration of five-coordinated Al. These results further support the concept that pressure-induced network structural transitions have direct implications for the macroscopic properties of high-pressure melts. Keywords: Calcium aluminosilicates, potassium aluminosilicates, aluminosilicate glasses and melts, glass properties, NMR spectroscopy, high-pressure studies, melt properties

Growth of [Si.sub.1?x][Ge.sub.x] nanodots on Si substrates is accomplished using single source gaseous precursors. It is found that on the nanodots they are relaxed and their compositions correlate with the molecular ratios in the precursors used in their fabrication.

Large-scale aligned silicon carbonitride (SiCN) nanotube arrays are synthesized by microwave-plasma-assisted chemical vapor deposition by using Si[H.sub.4], C[H.sub.4], and [N.sub.2] as precursors. With the increasing Si concentration, the SiCN nanotube has displayed favorable oxidation resistance, suggesting that SiCN nanotube is a promising candidate as stable field emitter.

The texturization of monocrystalline silicon wafers using sodium carbonate solution has been investigated. This etching process has been evaluated in terms of the surface morphology and the reflectance value. The results show that for low concentration of sodium carbonate the increase of texturing time decreases the reflectance value because of the change in morphology from hillocks to pyramidal; on the contrary for intermediate and high concentrations the increase of time has a detrimental effect on texturization because it increases both the pyramid sizes and their non-uniform distribution. However, a good cell performance could be obtained by etching at high concentrations and short times. Keywords: Monocrystalline silicon; Texturization; Reflectance; Sodium carbonate

The effects of growth parameters on deep levels in n-type 4H-SiC were investigated by deep level transient spectroscopy. It was seen that the formation of Z1/2 and EH6/7 centers were guided by the C/Si ratio and growth temperature rather than the growth rate.

In this work, we report on the determination of the optimum level of Si[O.sub.2] in [(CoCrPt).sub.1-x] [(Si[O.sub.2]).sub.x] perpendicular recording media. We have determined the optimum level via studies of magnetic viscosity which have been compared to recording properties. We find that the optimum level of Si[O.sub.2] is of the order of 10%. At this level, studies of the activation volume of reversal show that the grains become essentially exchange decoupled and that a further increase in the level of Si[O.sub.2] produces no further improvement in the decoupling. We also find that this level of Si[O.sub.2] corresponds to optimum recording performance and that increasing the level of Si[O.sub.2] further results in the production of a system with smaller grains where thermal loss is observed to increase dramatically. Index Terms--Activation volume, intergranular coupling, magnetic characterization, perpendicular recording media.

The fabrication of doubly stacked layers of silicon nanocrystals (nc-Si) in amorphous silicon nitride ([alpha]-Si[N.sub.x]) dielectric by plasma enhanced chemical vapor deposition and subsequent high-temperature thermal annealing is presented. Capacitance-voltage (C-V) and current-voltage (I-V) measurements are used to study the charge trapping phenomena and the results have confirmed the memory effects of the nc-Si, which has displayed capacitance hysteresis and asymmetric current peaks, respectively.

Brackets on the melting temperature of [K.sub.2] C[O.sub.3] were experimentally determined at 1.86 [+ or -] 0.02 GPa (1,163-1,167[degrees]C), 2.79 [+ or -] 0.03 GPa (1,187-1,195 [degrees]C), and 3.16 [+ or -] 0.04 GPa (1,183-1,189[degrees]C) in a piston-cylinder apparatus. These new data, in combination with published experiments at low pressure (

In-situ X-ray absorption spectroscopy at the Fe K-edge was used to characterize the local structural environment of [Fe.sup.2+] and [Fe.sup.3+] in silicate melts at high temperature (up to 1050 [degrees]C) in comparison to their quenched glassy analog at room temperature. Measurements were performed on binary alkali-silicate compositions and on haplogranitic compositions, which were doped with about 5 wt% [Fe.sub.2][O.sub.3]. Changes in the structural environment of Fe were evaluated by analyzing both the pre-edge feature and the first maximum of the EXAFS of the spectra. In most cases, the spectra collected at high temperature differed from those of the quenched samples. At reducing conditions, the melts showed slightly higher amounts of low-coordinated [Fe.sup.2+] than their glassy counterparts. This finding is consistent with results of earlier studies (e.g., Jackson et al. 1993), but the observed change in speciation is smaller than reported by these authors. At oxidizing conditions, glasses and melts displayed a more heterogeneous behavior. The spectra of alkali-silicate compositions indicate higher amounts of low-coordinated [Fe.sup.3+] in the melt, whereas no significant difference between melt and glass was observed for [Fe.sup.3+] in haplogranitic compositions, even if the latter are peralkaline. The amount of non-bridging O atoms in the glass/melt system appears to play an important role particularly for [Fe.sup.3+]. However, more complex relationships between Fe and other structural components, especially Al, are possible. Keywords: XAS (XAFS, XANES), Fe K-edge, high-temperature studies, Fe in silicate melts, melt properties, glass properties

It is well known that Ca[Cl.sub.2] and Mg[Cl.sub.2] can been used for dust control and soil stabilization in many fields. However, solutions of Ca[Cl.sub.2] and Mg[Cl.sub.2] are slightly acidic and their application is often forbidden in the area where acid is restricted. Furthermore, in wet seasons, Ca[Cl.sub.2] and Mg[Cl.sub.2] can be partly leached away by water and result in other pollution. In order to solve such problems, CaO, MgO and sodium silicate were individually mixed to the chlorides to reduce their acidity in the investigation. Based on a large number of experiments, the principal results are as follows: CaO, MgO, and sodium silicate cannot only reduce effectively the acidity of the solutions but also decrease greatly the water absorption capacity of the chlorides. The more CaO, MgO, and sodium silicate are added, the less its water absorption rate of the chlorides will be. At the same time, CaO, MgO, and sodium silicate can react with the chlorides, some ions on the surface of soil and dust particles, water and C[O.sub.2] in atmosphere, and their formation products can also bind dust and soil effectively. The binding principles of dust and soil are also explained in detail in this paper. DOI: 10.1061/(ASCE)0899-1561 (2007) 19:1 (10) CE Database subject headings: Chlorides; Dust; Absorption; Soil stabilization.

This study investigates partitioning of elements between immiscible aluminosilicate and borosilicate liquids using three synthetic mixtures doped with 32 trace elements. In order to get a good spatial separation of immiscible liquids, we employed a high-temperature centrifuge. Experiments were performed at 1,050-1,150[degrees]C, 1 atm, in sealed Fe and Pt containers. Quenched products were analysed by electron microprobe and LA ICP-MS. Nernst partition coefficients (D's) between the Fe-rich and Si-rich aluminosilicate immiscible liquids are the highest for Zn (3.3) and Fe (2.6) and the lowest for Rb and K (0.4-0.5). The plots of D values against ionic potential Z/r in all the compositions show a convex upward trend, which is typical also for element partitioning between immiscible silicate and salt melts. The results bear upon the speciation and structural position of elements in multicomponent silicate liquids. The ferrobasalt-rhyolite liquid immiscibility is observed in evolved basaltic magmas, and may play an important role in large gabbroic intrusions, such as Skaergaard, and during the generation of unusual lavas, such as ferropicrites.

The synchrotron radiation (SR) phase radiography, optical and scanning electron microscopies (SEM) and color photoluminescence are used to study the interaction of micropipes (MPs) with foreign polytype inclusions in 4H-SiC bulk crystals grown on 6H-SiC substrates. A model of a polytype inclusion interactions with MPs near the free surface of a growing crystal is developed, which has helped in understanding the pore formation and expansion in SiC bulk crystals.

Chromium K-edge X-ray absorption near-edge structure (XANES) spectra were recorded at room temperature for 27 CaO-MgO-[Al.sub.2][O.sub.3]-Si[O.sub.2] (CMAS) glass compositions quenched from melts equilibrated at various oxygen fugacities ([f.sub.[O.sub.2]]) at 1400 [degrees]C. Values of [Cr.sup.2+]+/ [summation]Cr were determined from the intensity of a shoulder on the main absorption edge, attributed to the 1s [right arrow] 4s transition, which is characteristic of [Cr.sup.2+] in these glasses. For each composition, [Cr.sup.2+]/[summation]Cr could be quantified as a function of [f.sub.[O.sub.2]], using a theoretical expression, from as few as three samples ([Cr.sup.2+]/[summation]Cr [approximately equal to] 0, 0.5, and 1). This allowed log K', or the reduction potential of the [Cr.sup.3+/2+] half-reaction, and hence the relative change in the ratio [[gamma].sup.melt.sub.[Cr.sup.3+][O.sub.0.15]]/ [[gamma].sup.melt.sub.[Cr.sup.2+] O], to be determined for each composition. At constant [f.sub.[O.sub.2]], log[[Cr.sup.2+]+/[Cr.sup.3+]] was found to decrease linearly with increasing optical basicity. The variation in log K' with composition is controlled by [[gamma].sup.melt.sub.[Cr.sup.3+][O.sub.0.15]], corresponding to the capacity of the melt to stabilize both the charge and the preferred solvation site of [Cr.sup.3+]. The method was then applied to spectra recorded in situ at 1400 [degrees]C for a synthetic mid-ocean ridge basalt (MORB) composition, allowing [Cr.sup.2+]+/[summation]Cr to be quantified in a Fe-bearing melt for the first time. [Cr.sup.2+]+/[summation]Cr was found to vary from ~0.45 at the nickel-nickel oxide (NNO) [f.sub.[O.sub.2]] buffer to ~0.90 at iron-wustite (IW). This indicates that [Cr.sup.2+] is likely to be the dominant oxidation state in terrestrial basaltic melts. Keywords: XANES spectroscopy, chromium oxidation states, silicate melts, MORB

Eight silicate unit vibrational modes were identified in a suite of PbO-Si[O.sub.2] glasses using micro-reflectance Fourier Transform infrared ([mu]R-FTIR) spectra that were transformed using the Kramers-Kronig relation. The transformed FTIR spectra, in the 800-1200 [cm.sup.-1] range, were deconvolved systematically into eight Voigt-shaped bands at centers that were predicted from the second derivative of the spectra. The area of the eight bands varied as a function of Si[O.sub.2] content, and these trends were combined with theoretical constraints to identify and assign the bands to seven provisional silicate units: Si[O.sup.4-.sub.4] (830 and 860 [cm.sup.-1]), [Si.sub.2][O.sup.6-.sub.7] (900 [cm.sup.-1]), [Si.sub.6][O.sup.12-.sub.18] (950 [cm.sup.-1]), [Si.sub.2[O.sup.4-.sub.6] (980 [cm.sup.-1]), [Si.sub.4][O.sup.6-.sub.11] (1010 [cm.sup.-1]), [Si.sub.2][O.sup.2-.sub.5] (1050 [cm.sup.-1]), and Si[O.sub.2] (1100 [cm.sup.-1]). The provisional units were then grouped according to their NBO/T values: NBO/T = 4 (Si[O.sup.4-.sub.4), NBO/T = 3 ([Si.sub.2][O.sup.6-.sub.7), NBO/T = 2 ([Si.sub.6][O.sup.12-.sub.18] and [Si.sub.2][O.sup.4-.sub.6), NBO/T = 1 ([Si.sub.4][O.sup.6-.sub.11] and [Si.sub.2][O.sup.2-.sub.5]) and NBO/T = 0 (Si[O.sub.2]). The derived quantities of each NBO/T unit compare favorably with nuclear magnetic resonance data for PbO-Si][O.sub.2] glasses reported in the literature. This new approach for determining glass structure is advantageous because it may be performed on small Fe-bearing samples with minimal preparation, and analyses are rapid and relatively inexpensive. Keywords: IR spectroscopy, glass structure, band fitting, PbO-Si[O.sub.2]

Reflectance versus incidence angle measurements have been performed from 5 to 152 nm on samples of SiC with a different C/Si ratio deposited with rf magnetron sputtering. The optical constants of the material at different wavelengths have been determined by using a curve-fitting technique of reflectance values versus incidence angle. Complementary measurements of the incident beam polarization, film thickness, surface roughness, and stoichiometry were performed to complete the analysis of the samples. OCIS codes: 240.0310, 310.0310, 310.6860, 160.4670.