2009. "Molecular Depth Profiling of Sucrose Films: A Comparative Study of C₆₀n⁺ Ions and Traditional Cs⁺ and O₂⁺ Ions." Analytical Chemistry 81(20):8272-8279. doi:10.1021/ac900553z Abstract Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling of sucrose thin films were investigated using 10 keV C60+, 20 keV C602+, 30 keV C603+, 250 eV, 500 eV and 1000 eV Cs+ and O2+ as sputtering ions. With C60n+ ions, the molecular ion signal initially decreases, and reaches a steady-state that is about 38-51% of its original intensity, depending on the energy of the C60n+ ions. On the contrary, with Cs+ and O2+ sputtering, molecular ion signals decrease quickly to the noise level, even using low energy (250 eV) sputtering ions. In addition, the sucrose/Si interface by C60+ sputtering is much narrower than that of Cs+ and O2+ sputtering. To understand the mechanisms of sputtering-induced damage by these ions, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to characterize the bottoms of these sputter craters. XPS data show very little chemical change in the C60+ sputter crater, while considerable amorphous carbon was found in the O2+ and Cs+ sputter craters, indicating extensive decomposition of the sucrose molecules. AFM images show a very flat bottom in the C60+ sputter crater, while the Cs+ and O2+ sputter crater bottoms are significantly rougher than that of the C60+ sputter crater. Based on above data, we developed a simple model to explain different damage mechanisms during sputtering process.
2009. "Changes in the quaternary structure of amelogenin when adsorbed onto surfaces." Biopolymers 91(2):103-107. doi:10.1002/bip.21095 Abstract The amelogenin protein is involved in the formation of highly controlled and anisotropic hydroxyapatite crystals in tooth enamel. Amelogenin is unique in that it self assembles to form supramolecular quaternary structures called “nanospheres,” spherical aggregates of amelogenin monomers typically 20-60 nm in diameter. Although nanospheres have been observed in solution, the quaternary structure of amelogenin adsorbed onto surfaces is not well known. A better understanding of the surface structure is of great importance, however, because the function of amelogenin depends on it. We report studies of the adsorption of amelogenin onto self-assembled monolayers (SAMs) containing COOH and CH3 end group functionality as well as single crystal fluoroapatite (FAP), a biologically relevant surface. The supramolecular structures of the protein in solution as determined by dynamic light scattering (DLS) were compared with the supramolecular structures of the protein physisorbed onto surfaces as studied by atomic force microscopy (AFM). We found that although our solutions contained only nanospheres of narrow size distribution, smaller structures such as monomers and dimers were observed onto both hydrophilic and hydrophobic surfaces. This suggests that amelogenin can adsorb onto surfaces as small structures that peel away or “shed” from the nanospheres that are present in solution.
2009. "Adsorption of Amelogenin onto Self-Assembled and Fluoroapatite Surfaces." Journal of Physical Chemistry B 113(7):1833-1842. Abstract Abstract. The interactions of proteins at surfaces are of great importance to biomineralizaton processes and to the development and function of biomaterials. Amelogenin is a unique biomineralization protein because it self-assembles to form supramolecular structures called “nanospheres,” spherical aggregates of monomers that are 20-60 nm in diameter. Although the nanosphere quaternary structure has been observed in solution, the quaternary structure of amelogenin adsorbed onto surfaces is also of great interest because the surface structure is critical to its function. We report studies of the adsorption of the amelogenin onto self-assembled monolayers (SAMs) with COOH and CH3 end group functionality and single crystal fluoroapatite (FAP). Dynamic light scattering (DLS) experiments showed that the solutions contained nanospheres and aggregates of nanospheres. Protein adsorption onto the various substrates was evidenced by null ellipsometry, x-ray photoelectron spectroscopy (XPS), and external reflectance Fourier transform infrared spectroscopy (ERFTIR). Although only nanospheres were observed in solution, ellipsometry and atomic force microscopy (AFM) indicated that the protein adsorbates were much smaller structures than the original nanospheres, from monomers to small oligomers in size. Monomer adsorption was promoted onto the CH3 surfaces and small oligomer adsorption was promoted onto the COOH and FAP substrates. In some cases, remnants of the original nanospheres adsorbed as multilayers on top of the underlying subnanosphere layers. This work suggests that amelogenin can adsorb by the “shedding” or disassembling of substructures from the nanospheres onto substrates and indicates that amelogenin may have a range of possible quaternary structures depending on whether it is in solution or interacting with surfaces.
2009. "New Approaches for Characterizing Sensor and Other Modern Complex Materials." ECS Transactions 19(6):137-148. doi:10.1149/1.3118546 Abstract Advances in understanding of sensor and other modern complex materials are often enabled by new research tools. This paper highlights three capability development themes used to identify new research tools to be provided to users of the U. S. Department of Energy’s Environmental Molecular Sciences Laboratory. These capability development directions address the importance of dynamic measurements in realistic environments, the need for increased resolution in three dimensional analyses as well as the importance of linking theory and experiment. Capability development involves expanding the range of operation for a number of important techniques, developing and applying new capabilities, and advancing methods of data processing. Examples of current developments are provided including those related to magnetic resonance, x-ray diffraction, application of a focused beam capability to fuel cell aging, and near real time analysis of XPS spectra.
2008. "Stardust in Antarctic Micrometeorites." Meteoritics and Planetary Science 43(8):1287-1298. Abstract We report the discovery of presolar silicate, oxide (hibonite) and (possibly) SiC grains from four Antarctic micrometeorites. The oxygen isotopic compositions of the eighteen presolar silicate (and one oxide) grains found are consistent with those observed previously in primitive meteorites and interplanetary dust particles, and indicate origins in oxygen-rich red giant or asymptotic giant branch stars. Four grains with anomalous C isotopic compositions were also detected. 12C/13C as well as Si ratios are similar to those of mainstream SiC grains; the N isotopic composition of one grain is also consistent with a mainstream SiC classification. Presolar silicate grains were found in three of the seven AMMs studied, and are heterogeneously distributed within these micrometeorites. Fourteen of the 18 presolar silicate grains and 3 of the 4 C-anomalous grains were found within one AMM, T98G8. The presence of magnesiowüstite, which forms mainly through the decomposition of carbonates, in AMMs without presolar silicates, and its absence in the presolar silicate-bearing micrometeorites, suggests that parent body processes (specifically aqueous alteration) may determine the presence or absence of presolar silicates in Antarctic micrometeorites.
2008. "A New Mechanism for Ozonolysis of Unsaturated Organics on Solids: Phosphocholines on NaCl as A Model for Sea Salt particles." Physical Chemistry Chemical Physics. PCCP 10(4):528-541. doi:10.1039/b712715d Abstract The ozonolysis of an approximately one monolayer film of 1-oleoyl-2-palmitoyl-sn-glycero-3-phosphocholine (OPPC) on NaCl was followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) at 23 °C. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and AUGER electron spectroscopy were used as complementary analytical techniques. Ozone concentrations ranged from 1.7 1012 to 7.0 1013 molecules cm-3 (70 ppb to 2.5 ppm). Upon exposure to O3, there was a loss of C=C accompanied by the formation of a strong band at ~1110 cm-1 due to the formation of a stable secondary ozonide (1,3,4-trioxolane, SOZ). The yield of the SOZ was lower when the reaction was carried out in the presence of water vapor at concentrations corresponding to relative humidities between 2 and 25 %. The dependencies of the rate of SOZ formation on the concentrations of ozone and water vapor are consistent with the initial formation of a primary ozonide (1,2,3-trioxolane, POZ) that can react with O3 or H2O in competition with its thermal decomposition to a Criegee intermediate and aldehyde. This interpretation is also consistent with the measured dependence of the SOZ yield on the ozone concentration. Estimates were obtained for the rate constants for the POZ thermal decomposition and for its reactions with O3 and H2O, as well as for the initial reaction of O3 with OPPC. The SOZ decomposed upon photolysis at > 300 nm, generating aldehydes, carboxylic acids and anhydrides. These studies show that the primary ozonide has a sufficiently long lifetime when formed on a solid substrate that direct reactions with O3 and H2O can compete with its thermal decomposition. In dry polluted atmospheres, ozone-alkene reactions may lead in part to the formation of stable secondary ozonides whose chemistry, photochemistry and toxicity should be taken into account in models of such regions.
2008. "Spectroscopic Characterization of Extracellular Polymeric Substances from Escherichia coli and Serratia marcescens: Suppression using Sub-Inhibitory Concentrations of Bismuth Thiols." Biomacromolecules 9(11):3079-3089. doi:10.1021/bm800600p Abstract Free and capsular EPS produced by Escherichia coli and Serratia marcescens were characterized in detail using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Total EPS production decreased upon treatment with sub-inhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount expressed. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, anti-fouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structures in addition to total EPS secretion.
2007. "Nucleation and Growth of MOCVD Grown (Cr, Zn)O Films – Uniform Doping vs. Secondary Phase Formation." Journal of the Electrochemical Society 154(3):D134-D138. doi:10.1149/1.2424422 Abstract We report a detailed study of chromium solubility and secondary phase formation in MOCVD grown (Cr, Zn)O-based films on silicon (100). Simultaneous deposition of 0.15M Cr(TMHD) and 0.025M Zn(TMHD) based precursors in an oxidizing environment with a flow ratio of 1:10 resulted in secondary phase formation rather than uniform Cr doping. Based on several surface and micro-structural techniques, we have identified nano-crystalline ZnCr2O4 and disordered Cr2O3 as the secondary Cr-containing phases that nucleate. Analysis suggests that ZnCr2O4 crystallites are dispersed throughout the film and that disordered Cr2O3 layer may form at the interface. These results reveal a strong tendency for Cr to exist in octahedral, rather than tetrahedral coordination.
2007. "Metalorganic chemical vapor deposition of carbon-free ZnO using the bis(2,2,6,6 tetramethyl-3,5-heptanedionato)zinc precursor." Journal of Materials Research 22(5):1230-1234. doi:10.1557/JMR.2007.0146 Abstract We report the growth of c-axis oriented ZnO films on silicon (100) single crystal substrates by MOCVD. A relatively uninvestigated precursor, Zn(TMHD)2, was used in a cold-wall MOCVD reactor. XPS and RBS analysis yielded a zinc-to-oxygen atom percent ratio of 0.98 and 1.00 at the surface and in the overall film, respectively indicative of stoichometric ZnO. Due to the presence of carbon at the surface, the excess oxygen at the surface was in the form of C-O bonding. The c-axis orientation was confirmed by HRTEM and XRD. We look at these results from a viewpoint of an ongoing effort to ensure cleaner decompositions using Zn(TMHD)2.
2007. "Fabrication of SiO2 Microdisk Arrays for Optics and Light Trapping Experiments." Microelectronic Engineering 84(12):2799-2803. doi:10.1016/j.mee.2007.02.001 Abstract We present a simple silicon based microfabrication process that produces an array of SiO2 microdisks using UV lithography. High-resolution SEM images of these structures indicate a smooth outer microdisk cavity surface. Photoemission measurements were performed at different spots on the microdisk and compared with measurements inside the cavity. A silicon to oxygen atomic concentration ratio of 1:2 obtained during depth profiling confirms that the entire microdisk is made up of stoichometric SiO2. In contrast, the inner cavity is mostly silicon with native oxide on top. We discuss the usefulness of SiO2 microdisks in optics for light trapping experiments.
2006. "Substrate Changes Associated with the Chemistry of Self-Assembled Monolayers on Silicon." Langmuir 22(13):5617-5624. doi:10.1021/la060153l Abstract Alkylsiloxane self-assembled monolayers (SAMs) are used in the semi-conductor industry, and more recently as proxies for organics adsorbed on airborne mineral dust and on buildings and construction materials. A number of methods have been used for removing the SAM from the substrate after reaction or use, particularly plasmas or piranha (H2SO4:H2O2) solution. However, the impact of these cleaning methods on the chemistry of subsequently formed SAMs on the surface is not known. We report here AFM, XPS, Auger and FTIR studies of changes in the silicon substrate on repetitive deposition and removal of SAMs by these two methods. It is shown that a layer of silicon oxide is formed, and the surface becomes very irregular and roughened, particularly for the piranha treatment. This layer of silica impacts the structure of SAMs attached to it and can serve as a reservoir for trace gases that adsorb on it, potentially contributing to the subsequent reactions of the SAM. The implications for the use of such surfaces as a proxy for reactions of organics on airborne dust particles and on structures in the boundary layer are discussed.
2006. "Bioassay Labels Based on Apoferritin Nanovehicles." Chembiochem 7(9):1315-1319. doi:10.1002/cbic.200600225 Abstract Here we report a nanoparticle label based on apoferritin nanovehicle loaded internally with markers for sensitive electrochemical DNA detection. The central cavity structure, the dissociation and reconstitute properties at different pHs of apoferritin provide a facile method to load and release markers. Hexacynoferrate(III) was used as model marker to load into the cavity of apoferritin protein cage. The loaded nanoparticle surface was functionalized with amino-modified DNA probe. Electrochemical DNA hybridization assay based on the hexacynoferrate loaded apoferritin nanovehicle could detect 23 atmol DNA targets in 50 ul sample solution. The concept could be readily extended to load other redox and fluorescence markers for bioassay applications. The new nanoparticle labels hold great promise for multi-target detection (in connection to nanoparticles loaded with different markers) and for enhancing the sensitivity of other bioassays.
2006. "Magnetic properties of epitaxial Co-doped anatase TiO2 thin films with excellent structural quality." Journal of Vacuum Science and Technology B--Microelectronics and Nanometer Structures 24(4):2012-2017. doi:10.1116/1.2216723 Abstract The heteroepitaxy of Co-doped anatase TiO2 on LaAlO3(001) has been refined with the goal of determining the relationship between structural quality and magnetic ordering. By significantly reducing the deposition rate and substrate temperature, well-ordered Co:TiO2 films with unprecedented crystalline quality were obtained by oxygen-plasma-assisted molecular beam epitaxy, as characterized by x-ray diffraction. These films exhibit uniform Co doping, with no evidence of Co segregation or secondary phases throughout the film depth or on the surface. Despite the improvement in crystalline quality and Co distribution, the films exhibit negligible ferromagnetism, with saturation moments of only ~0.1 B/Co. This loss of ferromagnetism is in stark contrast to faster-grown Co:TiO2 films, where a higher growth rate and substrate temperature typically result in lower crystalline quality, a highly non-uniform Co distribution, and average saturation moments of ~1.2 B/Co. The presence of ferromagnetism in faster-grown Co:TiO2 does not appear to arise from intrinsic point defects present in the bulk material, such as charge-compensating oxygen vacancies, but is instead attributed to the presence of extended structural defects.
2006. "Identification of Isotopically Primitive Interplanetary Dust Particles: A NanoSIMS Isotopic Imaging Study." Geochimica et Cosmochimica Acta 70(9):2371-2399. doi:10.1016/j.gca.2006.01.023 Abstract We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O,S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in 15N, including the largest 15N enrichments (~1300 ‰) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in 15N, leading to average bulk N isotopic compositions that are 15N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two 15N-rich hotspots have correlated 13C anomalies. CN–/C– ratios suggest that most of the 15N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the 17O and 18O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being “isotopically primitive” and consists of those IDPs that have anomalous bulk N isotopic compositions. These particles typically also contain numerous 15N-rich hotspots, occasional C isotopic anomalies, and abundant presolar silicate grains. In contrast, the other “isotopically normal” IDPs have normal bulk N isotopic compositions and, although some contain 15N-rich hotspots, none exhibit C isotopic anomalies and none contain presolar silicate or oxide grains. Thus, isotopically interesting IDPs can be identified and selected on the basis of their N isotopic compositions for further study. However, this distinction does not extend to H isotopic compositions. Although both H and N anomalies 2 are frequently attributed to the survival of molecular cloud material in IDPs and, thus, should be more common in IDPs with anomalous bulk N compositions, D anomalies are as common in normal IDPs as they are in those characterized as isotopically primitive, based on their N isotopes. This may be due to different effects of secondary processing on the isotopic systems involved.
2005. "Unusual aggregates from the oxidation of alkene self-assembled monolayers: a previously unrecognized mechanism for SAM ozonolysis?" Physical Chemistry Chemical Physics. PCCP 7:3605-3609. doi:10.1039/b508147e Abstract Airborne particles are important in climate, visibility, human health and atmospheric reactions. Organics associated with airborne particles are thought to be oxidized to polar, hygroscopic species with enhanced cloud-nucleating properties. We show that ozone oxidation of unsaturated organics on silica as a proxy for airborne dust leads to the formation of hydrophobic polymer balls which do not increase the uptake of water as previously assumed. We propose that atmospheric formation of hydrophobic polymers is generally controlled by the availability of water rather than acid, and hence is much more common in the lower atmosphere than previously recognized.
2005. "Formation of Epitaxial Oxide Nanodots on Oxide Substrate: Cu₂O on SrTiO₃(100)." Surface Science 589(1-3):120-128. Abstract X-ray photoelectron spectroscopy analysis during the oxygen plasma assisted molecular beam epitaxy, combined with atomic force microscopy, scanning Auger microscopy, and theoretical simulation studies have been used to evaluate the mechanism of single-phase Cu₂O nanodot formation on the SrTiO₃(100) surface. Formation of pure crystalline Cu₂O nanodots occurs rather in a narrow growth parameter window, outside which a coexistence of the multiple phases has been observed. Cuprous oxide nanodots on the SrTiO₃(100) substrate follow a growth mechanism which differs significantly from the growth modes observed for the majority of semiconductor quantum dots. Growth starts without wetting layer formation with appearance of well-ordered truncated square-based nanodots at submonolayer coverages. At the initial stages of growth, the nanodot size is only weakly changes with coverage and exponentially scales with temperature. After reaching a critical, temperature dependent dot density (~ 10¹³ cm-² for 760 K growth temperature), growth of mid-sized nanoclusters starts through coalescence, which is eventually followed by large dome-shaped cluster formation at higher coverages. The coexistence of the different types of the clusters at high coverages results in a multi-modal distribution of sizes and shapes.
2005. "Co-doped Anatase TiO₂ Heteroepitaxy on Si(001)." Journal of Applied Physics 97(7):073511-073511-10. doi:10.1063/1.1868854 Abstract Pure anatase TiO₂ and CoxTi₁-x O₂ (0.01 < x < 0.04) epitaxial thin films were deposited by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE) on Si(001) for evaluation as a potential dilute magnetic semiconductor material suitable for Si-based spintronic devices. Epitaxial growth on Si(001) was facilitated by the deposition of ¼or ½ ML Sr metal on the clean Si(001) surface to form an oxidation resistant silicide layer, followed by deposition of a thin SrTiO₃ buffer layer. Using ½ ML Sr metal to form the silicide allowed the deposition of 10 ML SrTiO₃ without oxidation of the Si interface. Epitaxial anatase could be grown on this heterostructure, although use of the oxygen plasma during deposition resulted in significant SiO₂ formation. Pure anatase films consisted of epitaxial anatase surface particles on a continuous anatase film. For Co-doped films, Co segregation to surface particles of epitaxial anatase was observed by Auger electron spectroscopy and transmission electron microscopy (TEM); faceting of the particles was observed for low Co doping concentrations. Although no secondary phases containing Co were observed in Co-doped anatase films by x-ray diffraction or TEM, x-ray absorption near edge spectroscopy indicated Co was present in the films as a mixture of Co(0), Co(II), and Co(III). All samples were ferromagnetic at room temperature; for lower Co concentrations, the ferromagnetic remanence (9%) and coercive field (100 Oe) were similar to phase-pure Co:TiO₂ / LaAlO₃. However, the presence of Co(0) under strongly oxidizing growth conditions known to oxidize the Si interface implies that under no deposition conditions can Co metal be eliminated while simultaneously protecting the Si interface from oxidation.
2005. "Simple Method for Estimating and Comparing of X-Ray Damage Rates." Journal of Vacuum Science and Technology A--Vacuum, Surfaces and Films 23(6):1740-1744. doi:10.1116/1.2073387 Abstract This note describes an approach for estimating and comparing rates or thresholds for x-ray induced specimen damage during surface analysis. The method uses a common reference material to compare x-ray damage rates reported in the literature and in publications to the rates of damage that may occur on a specific instrument. Although the method makes several assumptions that are only partially valid, results from a few damage data-sets appear acceptably consistent when comparing estimates to a time for 10% damage or signal change.
2005. "Electrochemical Corrosion Behavior of Low Carbon I-Beam Steels In Simulated Yucca Mountain Repository Environment." Corrosion 61(4):381-391. Abstract The electrochemical corrosion behavior of low carbon steel was examined in a simulated Yucca Mountain (YM) ground water by varying the electrolyte concentration and temperature under aerated and deaerated conditions. The results show that in deaerated conditions, the corrosion rate is low in the order of 0.6 to 4.5mpy, between 25 to 85oC, respectively. However, in aerated conditions the measured rates were expectedly very high, in the order of 3-55mpy in the above mentioned temperature levels. The rates initially increased up to 45oC, and a decreasing trend was observed with further increase in temperature from 65 to 85oC. The maximum corrosion rate was occurred at 45oC (54.5mpy). The low corrosion rates observed in all deaerated conditions, and in aerated solutions at higher temperatures were due to the preferential adsorption of Mg-species on the steel surface, as identified by XPS analyses. The results also indicate possible localized corrosion behavior of carbon steel in aerated conditions up to 45oC.
2004. "Dissolution and Growth of (10(1) over-bar4) Calcite in Flowing Water: Estimation of Back Reaction Rates via Kinetic Monte Carlo Simulations." Journal of Crystal Growth 262(1-4):503-518. Abstract Although calcite is an important mineral for many processes, there ae been relatively few simulations of it's growth and dissolution behavior. Such simulations are complicated by the multitude of defect types and by the asymmetry of the crystal. The present work combined a kinetic Monte Carlo (KMC) technique with the Kossel crystal (100) simple cubic concept and the Blasius boundary layer model to simulate the simultaneous growth and dissoution of the (1014)calcite cleavage surface in flowing water. The objective was to determine the activation energies of the back reaction (growth) from those of the forward reaction (dissolution) by obtaining agreement with cleavage-step morphologies and step dissolution velocities previously measured using an atomic force microscope (AFM). Blasius boundary layer conditions for the flowing fluid defined a model that treated the solid, the dissolution/growth interface, and the fluid kinetics. Microscopic reversibility and the laws of large numbers gave an expression for the back reaction activation energies in terms of the forward reaction energies and the entropy of mixing, a quantity estimated from the concentration of desorbates in a very small fluid layer adjacent to the interface. The KMC simulations produced cleavage-step morphologies that were in qualitive agreement with observations from AFM. The kinetics were dominated by diffusion events on the solid/fluid interface and in the fluid, as expected. The relative magniyudes of the desorption and adsorption activation energies were consistent with experimental data, entropic arguments, and crystal roughening theories. Quantitive agrrement with measured step velocities was best when the boundary layer parameters were given physically reasonable values, indicating that the model is self consistent.
2004. "Lateral Ordering of Microfabricated SiO₂ Nanotips." Electrochemical and Solid-State Letters 7(1):C7-C9. Abstract Micro -fabricated SiO₂ nano - tips are potentially useful as scanning tips in near field optical microscopy and sensor related functions. We report a process in which the rounding nature of isotropic etching is effectively used to micro -fabricate laterally ordered SiO₂ nano -tips. Combination of excessive isotropic wet etching of thermally grown SiO₂ with anisotropic etching of n type silicon along <100> planes leads to the formation of nano -tips with sharpness ~ 15 nm. Uniform periodic array of nano -tips form due to coalescence of excessively etched SiO₂ resulting in nano -tips length the separation between the original photolithographic features. Finally, the overall process of nano -tip formation is discussed by considering the roles of rapid isotropic etching of SiO₂ in buffered oxide etch solution, anisotropic etching of Si <100> in KOH solution, and slow SiO₂ etching in KOH solution.
2004. "Initial Stages of Oxide Nanodot Heteroepitaxial Growth: Cu2O on SrTiO3(100)." Applied Physics Letters 85(19):4481-4483. Abstract The growth mechanism in a heteroepitaxy of oxide nanodots is investigated by combination of the x-ray photoelectron spectroscopy (XPS), atomic force microscopy and theoretical modeling. In contrast to the majority of semiconductor systems, in the studied metal oxide system of Cu2O – SrTiO3(100) the growth process starts without wetting layer formation with appearance of small ( ~ 10 nm) square-based planar Cu2O nanodots. Continued deposition leads mainly to increase of the nanodot density, practically, without change of their size. Only after reaching some critical density (~ 1013 cm-2 for 760 K growth temperature), growth of scattered, significantly larger islands starts through the coalescence of small nanodots. XPS analysis suggests that the interface between small nanodots and substrate is abrupt with only weak Cu – O(SrTiO3) interaction.
2004. "Growth and Properties of molecular beam epitaxially grown ferromagnetic Fe-doped TiO2 rutile films on TiO2." Applied Physics Letters 84(18):3531-3533. Abstract We have grown epitaxial Fe-doped TiO₂ rutile films on rutile TiO₂(110) substrates, and have explored the resulting compositional, structural, morphological and magnetic properties. Clusters of mixed TiO₂ rutile and Fe₃O₄ form on the surface of a continuous rutile epitaxial film during growth. Room temperature ferromagnetism is observed, and is associated with the formation of secondary phase Fe₃O₄ rather than a true diluted magnetic oxide semiconductor.
2004. "X-ray Photoelectron Spectroscopic Analyses of Corrosion Products Formed on Rock Bolt Carbon Steel in Chloride Media with Bicarbonate and Silicate Ions." Corrosion Science 46(11):2629-2649. Abstract The passivation behavior of Yucca Mountain Repository rock bolt carbon steel in deaerated 3.5% NaCl solution containing SiO₂_₃ and HCO_₃ ions was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopic methods. Polarization results indicate that combinations of silicate and bicarbonate anions decrease the passive current density and raise the pitting potential. XPS results indicate the enrichment of silica at passive potentials and the formation of mixed FeCO₃ and silica film at lower potentials. This change in film composition was responsible for the changes in corrosion rate at lower and higher potentials. XPS results also support the thermodynamic data with regard to the occurrence of second oxidation peak observed in the polarization curves to be due to the oxidation of FeCO₃ to Fe2O₃
2003. "Beam Effects During AES and XPS Analysis." Chapter 9 in Surface Analysis by Auger and X-ray Photoelectron Spectroscopy. IM Publications, Chichester, United Kingdom. Abstract It is important to realize that any surface analysis method may alter the specimen in some way. Alterations that complicate the ability to collect the desired information are usually considered damage. Damage (like beauty) is in the eye of the beholder. In some cases, analysis-induced changes to a sample will have little or no impact on the information sought. In other cases, similar changes will be totally unacceptable and considered information-destroying damage. The analyst must therefore be able to recognize damage in all its various forms, understand its origins, and be able to compensate for, or limit, its effects on the analysis.
2003. "Appendix F: Comparing Beam Damage Rates Using Susceptibility Tables." In Surface Analysis by Auger and X-ray Photoelectron Spectroscopy, ed. D. Briggs and J.T. Grant, pp. 845-856. SurfaceSpectra Ltd. & IM Publications, Manchester, United Kingdom. Abstract Many research groups have observed electron and x-ray damage on a variety of materials. It is, of course, highly desirable to take advantage of the considerable experience gained by others in observing the presence of damage. Ideally, damage processes and rates would be determined for the samples of interest on the instrument in which measurements are to be made. However, in many cases such measurements are not possible and many important speciments are one of a kind. Several compilations of damage rates are available in the literature 1,2, or from Companies 3. In most cases the data from these potentially useful data sets are not likely to directly relate to the damage rates that might be observed for other instruments. There are two related reasons for this. First there is over an order of magnitude difference between x-ray damage rates observed on instruments in current use, as reported by Yoshihara and Tanaka.4 In addition, many new instruments have higher x-ray fluxes than many older instruments. The damage rates observed in the Pacific Northwest National Laboratory (PNNL) PHI Quantum 2000, are in the lower 1/3 of the instruments reported in Reference 4 but are approximately 5 times faster than those reported by Beamson and Briggs1 in 1992 for the Scienta 300 system.
2003. "Investigation of Copper(I) Oxide Quantum Dots by Near-Edge X-ray Absorption Fine Structure Spectroscopy." Chemistry of Materials 20(15):3939-3946. Abstract Copper oxide quantum dots (CuOQD) were grown in various thicknesses on different SrTiO₃(001) surfaces and were investigated by near edge x-ray absorption fine structure (NEXAFS) spectroscopy. The experimental growth conditions for the CuOQD were optimized to obtain Cu₂O as the major phase. The CuOQD grown on clean SrTiO₃(001) surfaces at 825 K or higher with p(O₂) of 9.0x10-7 Torr or above contain mostly CuO contrasting to CuOQD grown at 800 K with p(O₂) of ~7.0x10-7 Torr that contain primarily Cu₂O. Furthermore, it is established that there is a strong interaction between the SrTiO₃(001) surface and the first few monolayers of the CuOQD, which induces the formation of Cu(II). However, this interaction is mitigated with increasing thickness of CuOQD resulting in the exclusive formation of Cu₂O in the topmost layers. The influence of the SrTiO₃(001) substrate on the formation of CuOQD can be reduced by modifying the substrate surface using chemical treatment and/or energetic Au₂⁺ ion-beam irradiation, since the substrate effect results from the reaction between the substrate oxygen and the copper atoms from the CuOQD. Examination of the photochemical properties of these CuOQD shows that prolonged soft x-ray irradiation under vacuum reduces Cu(II), which is present as a minor impurity in the CuOQD.
2003. "Heteroepitaxial Growth of a Manganese Carbonate secondary Nano-Phase on the (101_4) Surface of Calcite in Solution." Surface Science 524(1-3):63-77. Abstract Heteroepitaxy of a manganese carbonate phase with nanometer dimensions on the (101_4) surface of calcite (CaCO₃) using an AFM has been observed in solution during dissolution of calcite when the ion activity product of Mn₂⁺ and CO₃₂- nears the solubility limit of MnCO₃. Growth-rate observations at different Mn concentrations, coupled with XPS and EPR measurements, suggest that the resulting phase is Mn₀․₅Ca₀․₅CO₃. These islands, while growing many microns in length along the [22_1] direction, have a uniform width in the range of 120-240 nm and a uniform height of approximately 2.7 nm, corresponding to nine atomic layers. The islands cease growing when they encounter step edges and have been observed to dissolve when undercut by a growing etch pit.
2003. "Electron Beam Damage in Poly(Vinyl Chloride) and Poly(Acrylonitrile) as Observed by Auger Electron Spectroscopy." Surface Science Spectra 10:67-79. Abstract AES spectra of spun-cast films of poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) were collected over a period of time to determine specimen damage during exposure to a 10kV electron beam. For the PVC, loss of chlorine was observed over a period of 203 minutes to the extent that the final chlorine concentration was only 20% of its original value. PAN exhibited a loss in nitrogen content over a period of 120 minutes, but the rate of damage to the polymer was significantly less than PVC. Figure 1 shows the atomic concentration in the PVC film as a function of dose (time). It takes a dose of approximately 7.0x10-5 Ccm-5 for the chlorine concentration to fall from its original value by 10% (one definition of critical dose). Figure 2 shows a similar drop in nitrogen concentration in the PAN film as a function of dose. For this polymer, it takes a dose of 1.3x10-3 Ccm-2 for the nitrogen concentration to fall by 10%.
2003. "Beam damage of poly(vinyl chloride) [PVC] as observed by x-ray photoelectron spectroscopy at 143 K, 303 K and 373 K." Surface Science Spectra 10:101-116. Abstract X-ray beam damage is often observed during surface analysis of beam sensitive materials as indicated in the introduction to this issue and in a wide variety of references. While damage occurs in a wide range of materials, those that are most susceptible to damage are materials that contain low energy covalent bonds such as polymers or other organic materials. Even amongst the relatively easily damaged polymers, there is a wide range of damage rates. The data reported in this submission was collected in the interest of comparing the rates of damage produced by x-ray and electron irradiation of different materials. The focus of this submission is x-ray damage of bulk poly(vinyl chloride) PVC since it is a readily available material. The temperature of the sample holder was controlled during irradiation of the PVC in order to determine the extent to which localized sample heating affects the rate of damage. PVC degrades by photoionization, resulting in the production of HCl through H and Cl bond cleavage. Bulk PVC has previously been the focus of an x-ray damage study involving many laboratories throughout the world. For comparison to the bulk PVC data, damage rates for thin films of poly(2-chloroethyl methacrylate) (PCEMA) are also reported for the same three temperatures. Measurements of several relatively common materials on one instrument can provide a data base that allows damage rates on one instrument to be linked or compared to other damage data in the literature.3 , , , In addition to the PCEMA films and bulk PVC, other data collected at the same x-ray parameters include thin films of PVC (for which damage rates are essentially identical to the bulk material) and of poly(acrylonitrile) PAN which is more stable that either PCEMA or PVC. An additional set of PVC data for a different instrument is also included in the volume. X-ray beams used for XPS produce less damage in materials than electrons used for AES analysis. This is due to both the weaker interaction between x-rays and materials (relative to electrons) and the deeper penetration of x-rays into the material producing a lower damage density. Although the rates of damage for x-rays and electrons differ, many of the processes are similar. Both electron and x-ray damage has been collected for PVC and PAN as reported in this volume of SSS8,9,12 and summarized in the introduction. The overall damage rates for PVC and PAN differ by an order of magnitude, but the ratios of the electron and x-ray damage rates for these two materials are nearly the same.1,7
2003. "Beam damage of poly(2-chloroethyl methylacrylate) [PCEMA] films as observed by x-ray photoelectron spectroscopy at 143 K, 303 K, and 373 K." Surface Science Spectra 10:80-100. Abstract X-ray beam damage is often observed during surface analysis of beam sensitive materials as indicated in the introduction to this issue and in a wide variety of references. While damage occurs in a wide range of materials, those that are most susceptible to damage are materials that contain low energy covalent bonds such as polymers or other organic materials. Even amongst the relatively easily damaged polymers, there is a wide range of damage rates. The focus of this submission is on poly(2-chloroethyl methylacrylate) [PCEMA] films. In order to determine the extent to which localized sample heating could influence damage rates the temperature of the substrate holding the PECMA was controlled during irradiation. PCEMA presumably degrades primarily by photo-ionization, resulting in the production of HCl through H and Cl bond cleavage. PCEMA has been recommended as a polymer for use as a reference for evaluating x-ray damage. PCEMA has been shown to be more sensitive to degradation than PVC which has also been used as a damage sensitive material useful for comparison of damage rates. Measurements of several relatively common materials on one instrument can provide a data base that allows damage rates on one instrument to be linked or compared to other damage data in the literature.3,4,5, Therefore for purposes of comparison, damage rates for bulk PVC at the same three different temperatures used for the PCEMA data have been collected and are also presented in this volume. Other data collected at the same x-ray parameters include thin films of PVC (for which damage rates are essentially identical to the bulk material) and of poly(acrylonitrile) PAN which is more stable that either PCEMA or PVC.
2003. "Clusters and Magnetism in Epitaxial Co-doped TiO₂ Anatase." Applied Physics Letters 82(8):1257-1259. Abstract We show that under certain conditions, highly Co-enriched Ti0₂ anatase clusters nucleate on epitaxial Ti0₂ anatase grown on LaA₁O₃(001) by oxygen plasma assisted molecular beam epitaxy. In the most extreme cases, virtually all incident Co segregates to the clusters, yielding a nanoscale ferromagnitic phase that is not ferromagnetic in homogeneous films of the same Co concentration. The nucleation of this phase simultaneous with continuous epitaxial film growth must be carefully monitored in order to avoid drawing false conclusions about the film structure
2003. "Introduction to Surface Science Spectra Data on Electron and X-ray Damage: Sample Degradation during XPS and AES Measurements." Surface Science Spectra 10(1-4):47-56. Abstract The types of damage to sample surfaces that can occur during X-ray or electron irradiation used during Auger electron spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) are summarized. The material and instrumental dependence of the rate and nature of damage formation or sample degradation are highlighted. Particular note is made of an enhanced susceptibility of thin films to damage. A simple method to enable comparison of published damage rates to what may be observed in a specific system is described and discussed in relation to data included in this journal volume. Strategies for detecting and minimizing damage are presented.
2002. "Interfacial Chemistry and the Performance of Bromine-etched CdZnTe Radiation Detector Devices." IEEE Transactions on Nuclear Science 49(4):2005-2009. Abstract The interfacial chemistry and composition of Pt electrodes sputter deposited on bromine-etched CdZnTe surfaces was studied by XPS, SIMS, AES, NRA and RBS. The interfacial composition of a functioning and a non-functioning CdZnTe detector shows significant differences. The degree of cation out-diffusion into the Pt overlayer and the in-diffusion of Pt into the CdZnTe correlate with the degree of oxidation found at the metal-semiconductor interface. Practically all the oxide present at the interface was found to be TeO₂. The results suggest that the inter-diffusion of the atoms and associated charges contribute to stoichiometric variations at the metal-semiconductor interface and influence the electrical performance of the devices.
2002. "Evidence for Localization of Reaction Upon Reduction of Carbon Tetrachloride by Granular Iron." Langmuir 18(20):7688-7693. Abstract The distribution of reaction sites on iron particles exposed to water containing carbon tetrachloride has been examined by measuring the locations of reaction products. The uniformity or localization of reaction sites has implications for understanding and modeling the reduction of environmental contaminants by iron in ground water systems. Granular iron surfaces similar to those being used for environmental remediation applications were studied using surfaces analysis techniques to develop an understanding of the physical and chemical structure of the surface and oxide films. Scanning Auger microscopy and imaging time-of-flight secondary ion mass spectrometry revealed that granular iron exposed to carbon tetrachloride-saturated water exhibits chloride-enriched regions occurred at pits rather than on th passive oxide film on the metal. Understanding the nature of the local solute reduction sites will play an important role in modeling the kinetics of reaction at passive iron oxide films in environmental systems.
2002. "Epitaxial Growth and Properties of MBE Grown Ferromagnetic Co-doped TiO₂ Anatase Films on SrTiO₃(001) and LaAlO₃(001)." Thin Solid Films 418(2):197-210. Abstract We have investigated the heteroepitaxial growth and materials properties of pure and Co-doped TiO₂ anatase on SrTiO₃(001) and LaAlO₃(001), grown by oxygen plasma assisted molecular beam epitaxy. This material is a promising new diluted magnetic semiconductor that shows large magnetization and a Curie temperature well above room temperature. We have found that epitaxial films with the highest crystalline quality and most uniform distribution of Co result when a rather slow growth rate (~0.01 nm/sec) is used over a substrate temperature range of 550 degrees Celcius to 600 degrees celcius. These conditions result in layer-by-layer growth of single-crystal films, and a very low density of extremely small nanocrystalline inclusions. In contrast, growth at a higher rate (~0.04 nm/sec) leads to extensive formation of secondary phase rutile nanocrystals to which Co diffuses and segregates. The rutile nanocrystals nucleate on the evolving anatase film surface in such a way that lattice strain between the two phases is minimized. Co appears to substitute for Ti in the lattice and exhibits a ⁺² formal oxidation state. Both pure and Co-doped films are typically n-type semiconductors despite the lack of intentional n-type doping, although a wide range of conductivities is observed.
2002. "Use and Limitations of Electron Flood Gun Control of Surface Potential During XPS: Two Non-homogeneous Sample Types." Surface and Interface Analysis 33:781-790. Abstract The ability of charge compensation methods to control the surface potentials for two types of non-homogenous samples is examined. Results demonstrate that two newer types of charge compensation systems have improved performance in relation to some previous flood gun methods and reaffirm the concept that a primary objective of charge compensation is to find conditions for which the surface potential of the specimen is as uniform as possible. However, experiments involving both flood gun use and specimen grounding, demonstrate that peak broadening and shifting can occur when two (or more) potentials are present in the region of analysis. Finally, the ability of interface charge to shift specimen potentials and measured binding energies demonstrates fundamental limitations to the absolute accuracy of binding energy measurements, but also remind us that charging phenomena can be used to obtain important information about the sample.
2001. "Scanning Auger Microscopy Studies of an Ancient Bronze." Journal of Vacuum Science and Technology A--Vacuum, Surfaces and Films 19(4 PT 1):1126-1133. Abstract We have conducted a scanning Auger microscopy (SAM) analysis on a Syrian bronze of the early I millennium BC. The objective was to derive a picture of modifications of the object's surface composition, induced by chemical attack by the ambient. Understanding degradation of ancient materials dating from a well-defined historical context provides information about long-term corrosion phenomena that is not possible from laboratory data. Such information is also useful for restoration and conservation efforts. While corrosion processes in the bulk are understood, this is not true for localized intergranular and transgranular surface corrosion in these materials. This requires information about local chemical composition and movement of ionic species that has not generally been available, and we find AES useful in accomplishing this task. SAM images of Cu, Sn and O, ~ 100-nm spatial resolution, and Auger point spectra show that Sn acts as a barrier against O2 attack, as it entirely traps this gas into a SnO2-like oxide, thus minimizing copper oxidation. Sub-micron spectromicroscopic evidence is given that S-induced corrosion occurs mainly via chemical attack along grain boundaries, where Sn has a low abundance and copper sulfides are detected. Lateral segregation of Sn and Cu domains is imaged with a spatial resolution of 15 nm. This result marks the best spatial resolution any analytical method has yet achieved in highlighting lateral chemical heterogeneities of ancient bronzes. Although archaeomaterials lie outside the mainstream applications of Auger techniques, this study provides convincing evidence that SAM can greatly advance our understanding of these materials.
2001. "Microscopic Effects of Carbonate, Manganese, and Strontium ions on Calcite Dissolution." Geochimica et Cosmochimica Acta 65 (3):369-379. Abstract Aqueous dissolution of the (1014) surface of calcite was observed at pH near 9 using an atomic force microscope equipped with a fluid cell. The influence of carbonate, Sr, and Mn ion concentrations were observed. Carbonste ions were shown to have a step-specific effect on calcite dissolution. At ow levels (5 mu-M) of carbonate, the retreat rate of the more structually open [441]+steps was than the retreat rate of the structurally confined [441]-steps, leading to anisotropic dissolution. Increasing the carbonate level to 200 mu-M decreased the rate of retreat of both steps, but the [411]+step was slowed to a much greater extent making the dissolution nearly isotropic. At high levels (800 mu-M) of carbonate, the rate of retreat of the [441]+step was slower than that of the [441]-step making dissolution anisotropic in the opposite sense to that observed at low levels of carbonate. This decrease in step velocity at high carbonate levels was attributed to a corresponding increase in the reaction (i.e., precipitation) as the solution approached saturation with respect to calcite, and thus is related to the rate of incorporation of calcium cations into the structure. In addition to changing the rate, this back reaction also altered the shape of etch pits formed by dissolution. Strontium cations were also shown to have a step-specific effect on calcite dissolution similar to that of carbonate, suggesting that strontium is preferentially incorporated into the [441]-step to a greater extent than strontium. When the solution exceeded saturation with respect to rhodochrosite, calcite dissolution was nearly isotropic. These results suggest that the small manganese ion (r = 83 pm), is readily incorporated into both [441]+ and [441]-steps, in contrast to the larger Ca (r = 100 pm) and Sr (r = 131 pm) cations, which are preferentially incorporated into the [441]+step.
2000. "Electron Beam Induced Damage of NaNO3 Single Crystals: An Energy, Temperature, and Quantum State Resolved Study." Journal of Physical Chemistry B 104(7):1563-1571. Abstract Electron-beam induced damage of NaNO3 single crystal is examined using laser resonance enhanced multiphoton ionization detection of the neutral desorption products, post irradiation temperature programmed desorption (TPD), secondary electron emission microscopy (SEEM) and Auger electron spectroscopy (AES). The damage initially involves destruction of the nitrate group and production of O (3PJ) and NO (2II) fragments with non-thermal energy distributions. Specifically, the O (3PJ) J-state distribution measured at 100 eV incident electron energy is 5 : 1.5 : 0.25 for J = 2 : 1 :0, the NO (2II) vibrational state distribution is 1 : 0.56 : 0.35 : 0.40 : 0.23 for v = 0 :2 : 2 : 3 : 4, and the NO (2II 1/2,3/2) rotational distribution has a high population of the upper (2II 3/2) spin-orbit component. Thermalized NO, O2 and NO2 are also produced and released, though the latter is a minor product. Yields of thermalized NO and O2 exhibit similar temperature dependencies with activation energies of 0.010 +- 0.004 and 0.1 +- 0.03 eV. These values are close to well-known activation energies of NO2 creation in the NaNO3 crystals. We suggest that the formation and desorption of thermalized molecular products involve NO2 defect states and unimolecular dissociation of NO3 which is activated by lattice phonons and vibrons. A significant amount of O2 gas is also released in post-irradiation thermal cycling from 110-440 K with peaks at ~260 and ~340 K. We associate the post-irradiation TPD of O2 with reactions involving O atoms released during thermal decompositions of {NO2 ...O} and ONOO. The SEEM image shows damage features and the AES spectra indicate that the irradiated region is depleted in both nitrogen and oxygen relative to Na. The elemental composition shows Na2O as a final product of the NaNO3 radiation decomposition. The ESD cross section using 100 eV electrons is at least ~10 -16cm2.
2000. "Effects of Precursors and Substrate Materials on Microstructure, Dielectric Properties and Step Coverage of (Ba,Sr)TiO3 Films Grown by Metalorganic Chemical Vapor Deposition ." Journal of Applied Physics 87(1):124-132. Abstract (Ba,Sr)TiO3 (BST) thin films have been grown on planar Ir/Si and Pt/Si substrates and on 3D Ir electrodes by metalorganic chemical vapor deposition (MOCVD) using two kinds of Beta diketonate-based BST precursors. Film growth was studied as a function of film thickness, composition, and substrate temperature. Growth rate was monitored by in-situ by a variety of techniques including x-ray photoelectron spectroscopy, Auger electron microscopy, atomic force microscopy, transmission and scanning electron microscopy, x-ray diffraction, and impedance analyzer. The results reveal that the two sets of BST precursors, albeit slightly different, show quite different reactvities that strongly affect the step coverage on the 3D structure. However, different reactivities have no apparent effect on the microstructure, surface morphology, and dielectric properties of the stoichiometric BST films. These properties strongly depend on the film composition, substrate material and growth temperature. in general, the BST films grown on Pt exhibit better crystalline quality, surface smoothness, and dielectric properties compared to those grown on Ir under the optimal growth conditions.
2000. "Effects of precursors and substrate materials on microstructure dielectric properties, and step coverage of (Ba, Sr)TiO3 films grown by metalorganic chemical vapor deposition." Journal of Applied Physics 87(1):124-132. Abstract (Ba,Sr)TiO3 (BST) thin films have been grown on planar Ir/Si and Pt/Si substrates and on three-dimensional (3D) Ir electrodes by metalorganic chemical vapor deposition using two kinds of bata-diketonate-based BST precursors. Film growth was studied as a function of film thickness, composition, and substrate temperature. Growth rate was monitored by in situ spectroscopic ellipsometry. The BST films were characterized ex situ by a variety of techniques including x-ray photoelectron spectroscopy, Auger electron microscopy, atomic force microscopy, transmission and scanning electron microscopy, x-ray diffraction, and impedance analyzer. The results reveal that the two sets of BST precursors, albeit slightly different, show quite different reactivities that strongly affect the step coverage on the 3D structure. However, different reactivities have no apparent effect on the microstructure, surface morphology, and dielectric properties of the stoichiometric BST films. These properties strongly depend on the film composition, substrate material, and growth temperature. In general, the BST films grown on Pt exhibit better crystalline quality, surface smoothness, and dielectric compared to those grown on Ir under the optimal growth conditions.