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Medium range order in amorphous thin films of Ge2Se3, a phase change memory material, was examined using electron nanodiffraction fluctuation electron microscopy. Variance measurements showed that medium range order existed at 0.36 and 0.58 Å-1. The film was not at equilibrium and contained a few monoclinic nanocrystals with weak Bragg maxima at 0.33, 0.54, and 0.63 Å-1, which are related to the GeSe2 equilibrium phase at this composition. We also determined the variance for amorphous silicon (a-Si) and amorphous silica (a-SiO2) and those results agree with others in the literature. It is expected that the medium range order is related to nucleation of the crystallization reaction in Ge2Se3. [ABSTRACT FROM AUTHOR]

The relationships among the equivalent oxide thickness (EOT), nanochemistry, and nanostructure of atomic layer chemical-vapor-deposited (ALCVD) Hf–O-based films, with oxide and nitrided oxide interlayers on Si substrates, were studied using x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in annular dark-field imaging (ADF), and parallel electron energy-loss spectroscopy (PEELS), capacitance–voltage, and leakage-current–voltage measurements. The XPS (Hf 4f binding energy shift) studies indicated the formation of Hf–O–Si bonds in as-deposited amorphous films, the amount of which was influenced by the interlayer composition and annealing conditions. After post-deposition annealing in N2 and O2, the Hf–O layers were nanocrystalline. Although HRTEM images showed a structurally sharp interface between the Hf–O layer and the interlayer, angle-resolved XPS, ADF imaging, and PEELS in the STEM revealed a chemically diffused HfSiOx region in between. This interdiffusion was observed by the detection of Si (using Si L edge) and Hf (using Hf O2,3 edge) in the Hf–O layer and the interlayer. For an annealed Hf–O/interlayer stack, with an ALCVD target thickness of 4.0 nm for the Hf–O layer on 1.2 nm of nitrided chemical oxide, the experimentally measured EOT and leakage current (at -1 V) were 1.52 nm and ∼10-8 A/cm2. A three-layer (1.2 nm interlayer of nitrided chemical oxide/compositionally graded, 2 nm region of HfSiOx/2 nm HfO2 layer) capacitor model was used to determine the respective contributions to the measured EOT, and the dielectric permittivity of the interlayer was found to be 6.06. These studies clearly indicate that a total EOT of 1 nm and below is attainable in the Hf–N–O–Si/Si–N–O system. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A 4 nm layer of ZrO[sub x] (targeted x∼2) was deposited on an interracial layer (IL) of native oxide (SiO, t∼1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 300°C. Some as-deposited layers were subjected to a postdeposition, rapid thermal annealing at 700°C for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr-O/IL/Si stack. The as-deposited Zr-O layer was amorphous ZrO[sub 2]-rich Zr silicate containing about 15% by volume of embedded ZrO[sub 2] nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-ZrO[sub 2] (t-ZrO[sub 2]) and monoclinic-ZrO[sub 2] (m-ZrO[sub 2]) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocrystals, as well as crystalline regions with defects, probably gave rise to lattice strains and deformations. The interracial layer (IL) was partitioned into an upper SiO[sub 2]-rich Zr silicate and the lower SiO[sub x]. The latter was substoichiometric and the average oxidation state increased from Si[sup 0.86+] in SiO[sub 0.43] (as-deposited) to Si[sup 1.32+] in SiO[sub 0.66] (annealed). This high oxygen deficiency in SiO[sub x] was indicative of the low mobility of oxidizing specie in the Zr-O layer. The stacks were characterized for their dielectric properties in the Pt/{Zr-O/IL}/Si metal oxide-semiconductor capacitor (MOSCAP) configuration. The measured equivalent oxide thickness (EOT) was not consistent with the calculated EOT using a bilayer model of ZrO[sub 2] and SiO[sub 2], and the capacitance in accumulation (and therefore, EOT and k[sub Zr-O]) was frequency dispersive, trends well documented in... [ABSTRACT FROM AUTHOR]

Studies the core-shell electronic absorption edges from thin specimens of silicon by using electron-energy-loss spectroscopy in a transmission electron microscope. Way to determine the composition and electronic structure of small crystalline or amorphous regions; Discussion on the Born approximation; Elemental and chemical effects in the edges.

Provides information on a study that obtained single-scattering electron-energy-loss microspectra for the oxidation series of tetrahedrally bonded silicon compounds and amorphous SiO[sub2]. Methodology of the study; Results and discussion on the study.

Presents a study that analyzed the valence shell electronic excitations in silicon and its refractory compounds using electron energy loss microspectroscopy. Calculation of the band-band contributions to the loss absorption cross section of the samples; Examination of the valence shell electronic excitations in silicon carbide and silicon nitride; Evaluation of the valence shell electronic excitations in silicon oxide.

Examines the band structure of hexagonal boron nitride using an ab initio linear combination of pseudoatomic-orbitals method. Method of calculation; Information on the X-ray emission spectra of the hexagonal boron nitride; Conclusions.

Presents a study which examined the application of a semiempirical self-consistent-field band calculation to near-edge fine-structure analysis of core-shell electronic absorption edges. Methods; Results; Discussion.

Deals with a study which evaluated various approximations in the calculations of electron energy-loss cross section and x-ray absorption coefficient of the silicon L[sub2,3] edge. Information on electron energy-loss spectroscopy; Methodology of the study; Results and discussion.

The nanostructure and magnetic properties of electrodeposited Co40Fe60 alloy films containing varying amounts of oxygen were investigated using transmission electron microscopy (TEM) and diffraction, secondary ion mass spectroscopy (SIMS), and superconducting quantum interference device (SQUID) measurements. Oxygen content in the CoFe deposit was controlled by electrolyte composition. Films were deposited on Si {100} substrates with thin Cu/Ti seed layer. Electron energy loss and x-ray spectroscopies showed that the low oxygen films contained intragranular FeO particles and that the high oxygen films contained Fe2O3 along grain boundaries. The films with oxide present at the grain boundary had increased coercivity and reduced saturation magnetization relative to the lower oxygen content films with intragranular oxide. The differences in magnetic properties between low oxygen and high oxygen concentration films were attributed to stronger mobile domain wall interactions with the grain boundary oxide layers relative to interactions with the intragranular oxide particles in the low oxygen specimens. [ABSTRACT FROM AUTHOR]

Storage of CO2 through mineral sequestration using olivine has been shown to produce environmentally benign carbonates. However, due to the formation of a rate-limiting reaction product layer, the rate of reaction is insufficient for large-scale applications. We report the results of altering the reactant solution composition and the resultant reaction mechanism to enhance the reaction rate. The products were analyzed for total carbon content with thermal decomposition analysis, product phase compositions with Debye-Scherrer X-ray powder diffraction (XRD), surface morphology with scanning electron microscopy (SEM), and composition with energy dispersive X-ray spectroscopy (EDXS). Carbon analysis showed that an increase in bicarbonate ion activity increased the olivine to carbonate conversion rate. The fastest conversion rate, 63% conversion in one hour, occurred in a solution of 5.5 M KHCO3. Additionally, SEM confirmed that when the bicarbonate ion activity was increased, magnesium carbonate product particles significantly increased in both number density and size and the rate passivating-reaction layer exfoliation was augmented. [ABSTRACT FROM AUTHOR]

Environmental transmission electron microscopy has been used to probe the mechanisms that govern Mg(OH)2 dehydroxylation and rehydroxylation processes at the near-atomic level. Dehydroxylation and rehydroxylation rates for these in-situ observations were controlled by regulating the water vapour pressure over the sample. Generally, the dehydroxylation proceeded via the nucleation and growth of an oxide lamella, resulting in the formation of oxide and/or oxyhydroxide regions within the reaction matrix. Competition between rapid-nucleation-slow-growth and slow-nucleation-rapid-growth mechanisms can dramatically impact the nanostructure formed during dehydroxylation. Steps, both parallel and perpendicular to the {0001} planes, were observed to form during dehydroxylation. The nanocrystalline MgO formed was highly reactive and readily rehydroxylated with increasing water vapour pressure. Rehydroxylation proceeded via the nucleation and growth of Mg(OH)2 crystals in the heavily dehydroxylated matrix. The partial edge dislocations formed (both parallel and perpendicular to {O001}brucite;) as the result of Mg(OH)2 nanocrystal intergrowth and anneal out with time, resulting in the formation of relatively large single crystals of Mg(OH)2. Such high mobility of Mg-containing species during rehydroxylation can be directly associated with the high chemical reactivity observed during rehydroxylation, which can facilitate key reaction processes, such as CO2 mineral sequestration. [ABSTRACT FROM AUTHOR]

Co36-40Fe64-60 films were electrodeposited on Cu/Si substrates from electrolytes containing variable amounts of Fe3+, to control the film's oxygen content. The films were body centered cubic with grain sizes of 10 to 20 nm. Analytical electron microscopy was used to determine oxygen distributions and bonding states in the films. Intergranular trivalent Fe2O3 was distributed along grain boundaries in the films with highest oxygen content. A lower volume fraction of intragranular FeO particles were observed in low oxygen content films. Intergranular Fe3+ oxide increased the coercivity and magnetoresistance and reduced the mass saturation magnetization relative to the low oxygen content films. [ABSTRACT FROM AUTHOR]