Lead zirconate titanate (PZT) films deposited by a hydrothermal method

We present a hydrothermal method to deposit PZT films. It uses a single-step hydrothermal process and user-friendly precursors. Pb(Zr_0.52,Ti_0.48)O₃ polycrystalline films, 5–10 μm thick, were produced in an aqueous basic solution (4M KOH) on a titanium substrate in a closed autoclave at 180 °C. A time-depending study to see the evolution of the films' formation is described. Some actuation testing is also presented.     

An STM investigation of sulfur and alkoxide adsorption on Ni(100)

The effect of sulfur on alkoxide formation and decomposition on the Ni(100) surface has been investigated with STM and LEED. At low coverage sulfur adsorbs into a p(2 x 2) structure, in agreement with LEED measurements and previous STM results. With increasing sulfur coverage, the p(2 x 2) structure saturates the surface and scattered domains of c(2 x 2) appear. Further increases in sulfur coverage affect increases in c(2 x 2) domain sizes; the state of the sulfur-covered surface up to 0.43 ML is characterized by p(2 x 2) and c(2 x 2) domains. STM measurements of the evolution of the sulfur-covered surface with D(2)S(g) adsorption are suggestive of sulfur nucleation and growth at multiple sites on the surface. Alkoxide formation on these surfaces was studied following exposure to ROH (R = CH(3), CH(3)CH(2), CH(3)CH(2)CH(2), and C(6)H(5)). The alkoxy surface intermediates adsorbed in p(2 x 2)-S vacancies and, in the case of phenoxy, between hollow sites. Agreement between the methoxy coverage determined by XPS and the fraction of the surface covered with p(2 x 2)-S, as determined by STM, suggests that the p(2 x 2) vacancies are the sites of methoxy adsorption, and hence the active sites for selective poisoning.     

An investigation of the surface enhanced Raman scattering (SERS) from a new substrate of silver-modified silver electrode by magnetron sputtering

'Pure' silver nanoparticles on silver electrode were prepared by magnetron sputtering. The silver-modified silver electrode has good stability and the silver nanoparticles on silver electrode have homogeneous size distribution. Compared with the silver colloid modified silver electrode, there were no any extraneous component ions on the electrode, for the modified silver nanoparticles are prepared by magnetron sputtering. Synchronously, we obtained much higher quality SERS spectra of adenine molecules on the silver electrode modified by magnetron sputtering (SEMMS), and the study of the adsorption behavior of adenine on the silver-modified silver electrode by surface enhanced Raman scattering (SERS) indicated that the silver-modified silver electrode was highly efficient substrates for SERS investigation. From the rich information on the SEMMS obtained from high-quality potential-dependent SERS, we may deduce the adsorption behavior of adenine and the probable SERS mechanism in the process. The probable reasons are given.     

Quantitative aspects of the desorption of copper from the silicon (100) surface

The desorption of copper from copper contaminated Si(100) samples has been investigated by thermal desorption spectroscopy (TDS). The samples have been contaminated with aqueous CuSO(4)/EDTA solutions. The amount of copper deposited on the Si surface was in the monolayer region as determined by means of ratio-tracer experiments. The copper is adsorbed on the sample surface in two different states, which could be resolved by TDS. By means of STM and XPS measurements it was possible to assign these two desorption peaks to the desorption of copper from carbon deposits, which had already been present before the contamination process, and to the desorption of copper from the bare Si surface.     

Quantitative aspects of the desorption of copper from the silicon (100) surface

The desorption of copper from copper contaminated Si(100) samples has been investigated by thermal desorption spectroscopy (TDS). The samples have been contaminated with aqueous CuSO₄/EDTA solutions. The amount of copper deposited on the Si surface was in the monolayer region as determined by means of ratio-tracer experiments. The copper is adsorbed on the sample surface in two different states, which could be resolved by TDS. By means of STM and XPS measurements it was possible to assign these two desorption peaks to the desorption of copper from carbon deposits, which had already been present before the contamination process, and to the desorption of copper from the bare Si surface.     

Oxidation of the (100) face of crystalline silicon

The density functional theory was used to calculate the equilibrium structures of clusters serving as models of the sequence of reaction steps in the oxidation of the (100) face of crystalline silicon and their relative heat effects. The formation of all the intermediates on the (100) face proceeds without activation energy, suggesting the feasibility of avalanche-like formation of an SiO₂ film. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 4, pp. 257–261, July–August, 2007.     

Linear nanostructure formation of aldehydes by self-directed growth on hydrogen-terminated silicon(100)

The self-directed growth of organic molecules on silicon surfaces allows for the rapid, parallel production of hybrid organic-silicon nanostructures. In this work, the formation of benzaldehyde- and acetaldehyde-derived nanostructures on hydrogen-terminated H-Si(100)-2x1 surface is studied by scanning tunneling microscopy in ultrahigh vacuum and by quantum mechanical methods. The reaction is a radical-mediated process that binds the aldehydes, through a strong Si-O covalent bond, to the surface. The aldehyde nanostructures are generally composed of double lines of molecules. Two mechanisms that lead to double line growth are elucidated.     

Viscoelastic and dielectric behaviour of thin films made from siloxane-containing poly(oxadiazole-imide)s

Siloxane-containing poly(oxadiazole-imide)s were prepared by polycondensation reaction of two aromatic diamino-oxadiazoles with a dianhydride containing tetramethylsiloxane moiety. Free-standing flexible films having good mechanical properties were made therefrom. The polyimides exhibited high thermal stability with initial decomposition temperature being above 440 °C and glass transition in the range of 165-183 °C. The dielectric constant values, measured at room temperature and in the frequency domain of 1 Hz-1 MHz, are in the range of 2.69-2.90, being significantly lower in comparison with that of Kapton HN® film, whose dielectric constant values ranged from 3.13 to 3.24. The dielectric loss values are low, in the same range with those of Kapton HN®. The dielectric spectroscopy data corroborated with the dynamo-mechanical analysis ones showed distinct sub-glass transitions for these polymers: γ relaxations with activation energies of 44 and 45 kJ/mol, and a β relaxation with an activation energy of 107 kJ/mol. The dielectric properties are discussed in comparison with those of Kapton HN® film measured under the same conditions.     

Stimulus-responsiveness and drug release from porous silicon films ATRP-grafted with poly(N-isopropylacrylamide)

In this report, we employ surface-initiated atom transfer radical polymerization (SI-ATRP) to graft a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), of controlled thickness from porous silicon (pSi) films to produce a stimulus-responsive inorganic-organic composite material. The optical properties of this material are studied using interferometric reflectance spectroscopy (IRS) above and below the lower critical solution temperature (LCST) of the PNIPAM graft polymer with regard to variation of pore sizes and thickness of the pSi layer (using discrete samples and pSi gradients) and also the thickness of the PNIPAM coatings. Our investigations of the composite's thermal switching properties show that pore size, pSi layer thickness, and PNIPAM coating thickness critically influence the material's thermoresponsiveness. This composite material has considerable potential for a range of applications including temperature sensors and feedback controlled drug release. Indeed, we demonstrate that modulation of the temperature around the LCST significantly alters the rate of release of the fluorescent anticancer drug camptothecin from the pSi-PNIPAM composite films.     

Microwave frequency dielectric properties of poly(vinylidene fluoride) films

The frequency dependence of dielectric constant ?′, dielectric loss ?″, and dielectric anisotropy were determined for poly(vinylidene fluoride) (PVDF) in microwave frequencies from 4 to 13 GHz. The ?′ and ?″ for PVDF films decreased with increasing frequency. Both ?′ and ?″ were larger in the transverse direction than in the machine direction or draw direction, but the values at 12 GHz were smaller than those observed at 4.0 GHz. The angular dependence of ?″ at microwave frequency reflects the orientational distribution of molecules in the amorphous region. The orientation function was determined to be about 0.04 and 0.01 for uniaxially and biaxially stretched PVDF, respectively. © 1995 John Wiley & Sons, Inc.     

Density control of dodecamanganese clusters anchored on silicon(100)

A synthetic strategy to control the density of Mn12 clusters anchored on silicon(100) was investigated. Diluted monolayers suitable for Mn12 anchoring were prepared by Si-grafting mixtures of the methyl 10-undecylenoate precursor ligand with 1-decene spectator spacers. Different ratios of these mixtures were tested. The grafted surfaces were hydrolyzed to reveal the carboxylic groups available for the subsequent exchange with the [Mn12O12(OAc)16(H2O)4]4 H2O2 AcOH cluster. Modified surfaces were analyzed by attenuated total reflection (ATR)-FTIR spectroscopy, X-ray photoemission spectroscopy (XPS), and AFM imaging. Results of XPS and ATR-FTIR spectroscopy show that the surface mole ratio between grafted ester and decene is higher than in the source solution. The surface density of the Mn12 cluster is, in turn, strictly proportional to the ester mole fraction. Well-resolved and isolated clusters were observed by AFM, using a diluted ester/decene 1:1 solution.     

Stoichiometry-dependent chemical activity of supported MgO(100) films

Here, we show that the stoichiometry and, consequently, the chemical activity toward hydroxylation of MgO(100) films grown by reactive deposition on Ag(100) strongly depend on the O(2) partial pressure during film growth. Oxygen-deficient films undergo dramatic relative oxygen uptake either by exposure to a partial pressure of water vapor or by aging in vacuum for a sufficiently long time. Conversely, on stoichiometric monolayer MgO islands, photoemission analysis of the O 1s level and scanning tunneling microscopy images are consistent with the prediction that dissociative adsorption of water occurs only at the borders of the islands.     

Angle-resolved photoemission from oriented films of lead phthalocyanine on A Cu(100) surface

The orientation of large planar lead-phthalocyanine (Pb-PC) molecules relative to a Cu(100) single-crystal substrate was determined for thin films in a     

Photochemistry on ultrathin metal films: strongly enhanced cross sections for NO2 on Ag/Si(100)

The surface photochemistry of NO(2) on ultrathin Ag(111) films (5-60 nm) on Si(100) substrates has been studied. NO(2), forming N(2)O(4) on the surface, dissociates to release NO and NO(2) into the gas phase with translational energies exceeding the equivalent of the sample temperature. An increase of the photodesorption cross section is observed for 266 nm light when the film thickness is decreased below 30 nm despite the fact that the optical absorptivity decreases. For 4.4 nm film thickness this increase is about threefold. The data are consistent with a similar effect for 355 nm light. The reduced film thickness has no significant influence on the average translation energy of the desorbing molecules or the branching into the different channels. The increased photodesorption cross section is interpreted to result from photon absorption in the Si substrate producing electrons with no or little momenta parallel to the surface at energies where this is not allowed in Ag. It is suggested that these electrons penetrate through the Ag film despite the gap in the surface projected band structure.     

Coatings with thermally switchable surface energy produced from poly(ethylene oxide)-poly(dimethylsiloxane) block copolymer films

This work explores coatings with thermally switchable wetting behavior, based on block copolymers that possess both hydrophilic and hydrophobic segments. The amphiphilic block copolymers were synthesized by coupling allyl-ended poly(ethylene oxide) (PEO) and hydride-ended poly(dimethylsiloxane) (PDMS) oligomers via a Pt catalyst. One near-symmetric diblock possessed an order-disorder transition temperature (T_ODT) of 64 °C. When cooled through T_ODT in ambient air, the PDMS domains wet the film's surface, producing a hydrophobic coating with a water contact angle (CA) = 90°. However, when cooled in humidified air, hydrophilic PEO domains form at the surface, yielding CA = 30–40°. The coatings can be reversibly switched between the two states by reheating above T_ODT, in the appropriate environment, and then cooling, rapidly generating the desired room-temperature surface wettability. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 135–140     

In situ growth of epitaxial cerium tungstate (100) thin films

The deposition of ceria on a preoxidized W(110) crystal at 870 K has been studied in situ by photoelectron spectroscopy and low-energy electron diffraction. Formation of an epitaxial layer of crystalline cerium tungstate Ce(6)WO(12)(100), with the metals in the Ce(3+) and W(6+) chemical states, has been observed. The interface between the tungsten substrate and the tungstate film consists of WO suboxide. At thicknesses above 0.89 nm, cerium dioxide grows on the surface of Ce(6)WO(12), favoured by the limited diffusion of tungsten from the substrate.     

Removal of strontium from an aqueous solution using co-precipitation followed by microfiltration (CPMF)

This study characterized the removal of strontium from an aqueous solution via co-precipitation followed by microfiltration (CPMF) on a lab-scale. Sodium carbonate was used as the precipitating agent. Ferric chloride was added to a settler at a dosage of 20 mg/L to improve strontium removal, and it was added to a membrane separator at a dosage of 10 mg/L to reduce membrane fouling. The concentration of strontium in the raw water used in this study was about 5 mg/L. In two intermittent tests, where dosages of sodium carbonate were 2000 mg/L and 1000 mg/L, the mean decontamination factors (DFs) were 237 and 158 and the mean concentration factors (CFs) were 288 and 462, respectively. Although the mean DF value was lower when the sodium carbonate dosage was 1000 mg/L instead of 2000 mg/L, the rate at which the specific flux (SF) of the membrane declined decreased as the amount of the effluent treated increased. The problem of strontium release at the beginning of the operation was controlled by a continuous test in which the dosage of sodium carbonate still was 1000 mg/L and the other parameters were the same as in the other tests. The results showed that the mean DF and CF were 157 and 480, respectively.     

Adsorption of transition metal atoms on the NiO(100) surface and on NiO/Ag(100) thin films

We have studied the adsorption of Au, Pd, and Pt atoms on the NiO(100) surface and on NiO/Ag(100) thin films using plane wave DFT+U calculations. The scope of this work is to compare the adsorption properties of NiO, a reducible transition metal oxide, with those of MgO, a simple binary oxide with the same crystal structure and similar lattice parameter. At the same time, we are interested in the adsorption characteristics of NiO ultra-thin films (three atomic layers) deposited on Ag(100) single crystals. Also in this case the scope is to compare NiO/Ag(100) with the corresponding MgO/Ag(100) films which show unusual properties for the case of Au adsorption. The results show that the transition metal atoms bind in a similar way on NiO(100) and NiO/Ag(100) films, with Pt, Pd, and Au forming bonds of decreasing strength in this order. No charging effects occur for Au adsorbed on NiO/Ag(100) films, at variance with MgO/Ag(100). The reasons are analyzed in terms of work function of the metal/oxide interface. Possible ways to modify this property by growing alternate layers of MgO and NiO are discussed.     

Sr掺杂对CaO(100)表面吸附甲醇影响的分子模拟

借助分子模拟手段,研究了锶掺杂对氧化钙表面甲醇吸附行为的影响。构建了甲醇在CaO(100)和CaO(100)-Sr表面吸附的模型,计算了甲醇在氧化钙表面的吸附能和解离活化能,分析了甲醇在氧化钙表面成键的态密度以及锶掺杂前后甲醇在氧化钙表面电荷布局和差分电荷密度,评估了锶掺杂量对氧化钙表面甲醇吸附性能的影响。结果表明,锶掺杂能够显著强化氧化钙对甲醇的吸附性能,降低甲醇的解离活化能,且吸附性能随锶掺杂量的增加而增强;甲醇在氧化钙表面吸附时活化,锶掺杂后活化程度增加。