Oxygen-deficient Species Research Articles

Methods for Direct Deposition of Copper on Glass Substrates

The properties of glass make it an attractive substrate material in a number of applications such as interposers, RF modules and opto-electronics. Smooth surfaces and low dielectric constant have been shown to reduce transmission loss in high frequency applications and improve the Q factor when used as an inductor substrate. Transparency, electrical insulation, low cost, freedom of shape, and potential for roll to roll or large area panel processing also can be beneficial. Shortcomings such as low thermal conductivity and difficulty in via formation are continually improving, therefore development of the metallization technology is also important. As economy is a major incentive for developing glass packaging technology, high cost fabrication techniques hinder the potential for application. To contribute to glass processing development, recent advances in research of methods for copper deposition directly on glass substrate are discussed where copper seed layers are deposited followed by electrolytic copper plating, then a thermal treatment. Two methods of copper seed layer deposition were investigated. One is by an electroless plating technique developed for deposition on a nanometer scale thick solution processed TiO2 layer formed on the glass surface. The electroless seed layer deposition method utilizes a Pd amino acid complex bearing a cationic moiety that is selectively adsorbed into TiO2 layer material for catalyst deposition. The other seed layer deposition method investigated was by a high power, low vacuum sputtering technique in combination with optimized plasma treatment of the glass surfaces. Because high vacuum is not necessary, expensive vacuum equipment is not required and chamber evacuation is rapid. After plating, thermal treatments caused a reaction at the glass-copper interface which chemically bonded the glass and copper resulting in high adhesion while maintaining smooth interfaces. The methods are illustrated in the attached scheme. In the electroless plating method, TiO2 + Cu reacted to form Ti2O3/Cu2O at the interface after thermal treatment and form SiO2 + Cu, SiO/Cu2O in the sputtering case. The formation of oxygen deficient species in both cases was found to manifest with the adhesion of Cu plating to the glass substrate. However, in the sputtering method with higher thermal treatment temperatures, Cu diffusion into the glass surface was observed with a further increase in adhesion. When the sputtered samples were heated above 500°C, the mode of delamination in peel strength tests changed from interface delamination to destruction of the glass surface layer where glass was observed on the delaminated copper layer. In the electroless plating case, even when adhesion strength was close to 1.5 kN/m, delamination always occurred at the TiO2-Cu interface. Both seed layer deposition methods present pros, cons, and unique characteristics that will be discussed in detail. The TiO2 and electroless seed layer can be deposited by economic solution processing and be applied to large area. Alternatively, the low vacuum sputter method consumes very little time compared to electroless plating methods and at less energy and economic cost compared to conventional sputtering. After the thermal treatment, both methods resulted in 20 mm thick copper deposits with 90° peel strength of over 1 kN/m for aluminoborosilicate glass. Using the electroless plating technique ca. 1 kN/m for quartz glass and ca. 0.5 kN/m for alumina and alumina nitride ceramics was attained. Compatibility with subtractive and semi-additive patterning methods were illustrated, and environmental endurance evaluations performed. The electroless plating process is currently in the evaluation stage for application in industrial scale manufacture. Figure 1

Origin of passivation in hole-selective transition metal oxides for crystalline silicon heterojunction solar cells

Abstract

Ethanol Vapour Sensing Property of Nitrogen Doped ZnO Fabricated by Spray Pyrolysis

In this paper, gas sensing property of a nitrogen doped ZnO was studied. nanofilms of pure and nitrogen-doped ZnO (0.1, 0.2 and 0.3 normality) were prepared on glass substrate by spray pyrolysis technique. These films were fired at 450°C for two hours in air atmosphere. nanobehavior of the films was confirmed by XRD and SEM analysis. Gas sensing behavior of the films was tested in static gas sensing system. Films were exposed to different gases as LPG.NH3, NO2, Ethanol vapour and CO2 at different ppm concentrations and different operating temperatures. Pure ZnO films showed poor sensing behavior. At 150°C, films of N-doped ZnO (0.3 normality) showed good sensing for Ethanol vapours. The gas sensitivity was determined as 86.8% for 200 ppm of Ethanol vapours. When compared with pure ZnO, the nitrogen doped ZnO films possessed more oxygen deficient species. Due to this crystal defects arising from nitrogen doping, the improvement in gas sensing property of ZnO may be argued. Keywords: Spray pyrolysis; ZnO; N; XRD; SEM; LPG

DFT Studies and Experiments on Biocatalytic Centers: Structure, Vibrations, and Core Excitations of the K[VO(O2)Hheida] Complex

Geometric and electronic properties of the K[VO(O2)Hheida] complex, which serves as a functional model for vanadium haloperoxidase enzymes, as well as of the molecular ions (VO(O2)Hheida)− and (VO(O)Hheida)− are evaluated using density-functional theory (DFT). Theoretical results of equilibrium structures, vibrational excitations, oxygen 1s core ionization and excitation are compared with measured data. The theoretical equilibrium structure of the K[VO(O2)Hheida] complex agrees quite well with the corresponding molecular structure in crystalline K[VO(O2)Hheida]·2(H2O) and differs only a little from that of the (VO(O2)Hheida)− ion. The potassium appears in the K[VO(O2)Hheida] complex as a positive K+ species binding only electrostatically with no orbital hybridization to the (VO(O2)Hheida)− part, which is also obvious from the respective orbital analyses and densities-of-states. The vibrational modes of peroxo and vanadyl oxygen in K[VO(O2)Hheida] are strongly coupled, and the calculated excitation energies can explain details of the experimental infrared and Raman spectra. The theoretical O 1s core ionization potentials (IP) vary between the different oxygen species and are consistent with results from X-ray photoemission (XPS). Theoretical O 1s core excitation spectra are confirmed by results from O K-edge NEXAFS measurements for crystalline K[VO(O2)Hheida]·2(H2O) under oxygen and helium pressure. The difference between the two experimental spectra can be explained by the presence of oxygen-deficient species based on the theoretical findings for the (VO(O)Hheida)− species.

Gas-sensing property of a nitrogen-doped zinc oxide fabricated by combustion synthesis

Among the various factors affecting the gas-sensing performance of ZnO, crystal defects have attracted less attention. In this letter, the gas-sensing property of a nitrogen doped ZnO powder was studied in detail in comparison with a nitrogen-free two-dimensional porous ZnO flake, which has been reported to possess a unique morphology favoring the gas-sensing performance. The nitrogen doped ZnO powders, which are several hundred nanometers in size, were fabricated in a flash by a solution combustion approach. The N/Zn atomic ratio was determined to be 0.04 by an elemental analysis. When compared with the nitrogen-free porous ZnO flakes, the nitrogen doped ZnO particles possessed more oxygen deficient species within the matrix of ZnO, and in turn exhibited a significantly improved gas-sensing property for detecting ethanol and acetone. The crystal defects arising from the nitrogen doping are thus argued to be more effective to improve the gas-sensing property of ZnO when compared with other efforts to control the particle size, surface area and the particulate morphology.

Kinetic study of NO reduction on carbon-supported chromium catalysts

Direct reduction of NO on carbon supported chromium catalyst and in the presence of reducing agent, such as C3H6 and CO, has been studied. For the direct NO reduction on the catalyst, a kinetic study has been carried out considering that adsorption of NO takes place on an activated chromium site. This activated chromium site, an oxygen deficient chromium catalysts, is generated by the reaction between a chromium site and an unstable carbon site, obtained by decomposition of carbon–oxygen complexes. The following step was the dissociative chemisorption of adsorbed NO by a neighboring carbon site. The rate determining step for the direct NO reduction is the formation of CO2, associated to the chromium catalyst regeneration. In the presence of a reducing agent, the proposed mechanism considers the chemisorption of C3H6 or CO on the chromium site, followed by the activation (reduction) of this site to obtain an oxygen-deficient species, which interacts with NO in gas phase, when propylene is used as reducing agent. The presence of CO favors other reaction pathway for the regeneration of the chromium catalyst, increasing the activity. Both models represent reasonably well the experimental data. XPS and thermodynamic results support the validity of the models proposed.

Cluster generation under pulsed laser ablation of zinc oxide

Neutral and cationic Zn n O m clusters of various stoichiometry have been produced by nanosecond laser ablation of ZnO in vacuum and investigated by time-of-flight mass spectrometry. Particular attention was paid to the effect of laser wavelength (in the range from near-IR to UV) on cluster composition. Under 193-nm laser ablation, the charged clusters are essentially substoichiometric with $\mathrm{Zn}_{n}\mathrm{O}_{n-1}^{+}$ and $\mathrm{Zn}_{n}\mathrm{O}_{n-3}^{+}$ being the most abundant series. Both sub- and stoichiometric cationic clusters are generated in abundance at 532- and 1064-nm ablation whose composition depends on the cluster size. The reactivity of small stoichiometric $\mathrm{Zn}_{n}\mathrm{O}_{n}^{+}$ clusters (n<11) toward hydrogen is found to be high, while oxygen-deficient species are less reactive. The neutral plume particles are mainly stoichiometric with Zn4O4 tetramer being a magic cluster. It is suggested that the Zn4O4 loss is the dominant fragmentation channel of large zinc oxide clusters upon electron impact. Plume expansion conditions under ZnO ablation with visible and IR laser pulses are shown to be favorable for stoichiometric cluster formation.

Oxidation of CO by Aluminum Oxide Cluster Ions in the Gas Phase

Small aluminum oxide cluster cations and anions, produced by laser vaporization, were investigated regarding their reactivity toward CO and N2O employing guided-ion-beam mass spectrometry. Clusters with the same stoichiometry as bulk alumina, Al2O3, exhibited atomic oxygen transfer products when reacted with CO, suggesting the formation of CO2. Anionic clusters were less reactive than cations but showed higher selectivity towards the transfer of only a single oxygen atom. Cationic clusters, in contrast, exhibited additional products corresponding to the sequential transfer of two oxygen atoms and the loss of an aluminum atom. To determine if these stoichiometric clusters could be generated from oxygen-deficient species, clusters having a stoichiometry with one less oxygen atom than bulk alumina, Al2O2, were reacted with N2O. Cationic clusters were found to be selectively oxidized to Al2O3(+), while anionic clusters added both one and two oxygen atoms forming Al2O3(-) and Al2O4(-). The oxygen-rich Al2O4(-) cluster exhibited comparable reactivity to Al2O3(-) when reacted with CO.

Chemical State and Refractive Index of Mg-Ion-Implanted Silica Glass

The chemical state of implanted Mg atoms has been studied in 2.48 ×1017 Mg+ ions cm-2-implanted silica glass by X-ray photoelectron spectroscopy. It was found that Mg atoms were coordinated with oxygen atoms, irrespective of the heat treatment at 900°C in an argon gas atmosphere. Mg ion implantation caused oxygen deficient species (SiOx) and increased the refractive index by about 5%. The oxygen deficient species and the refractive index change were stable against the heat treatment.

Reduction of the Phosphododecamolybdate Ion by Phosphonium Ylides and Phosphanes

The reaction of phosphonium ylides with [PMo12O40]3− consists of successive single electron transfers leading to the formation of the 1e- and 2e-reduced polyoxomolybdates [PMo12O40]4− and [PMo12O40]5−. The ylide is converted into the corresponding phosphonium cation via a radical-cation intermediate. The reaction of phosphanes follows the same pathway but subsequent reactions with residual water produce protons which induce the disproportionation of [PMo12O40]4−. Authentic samples of heteropoly blues in different protonation states have been obtained from the reaction of phenyllithium with [PMo12O40]3− and subsequent protonation with triflic acid. On the basis of electrochemical and spectroscopic data, the reaction product of [PMo12O40]3− with triphenylphosphane, which has been previously described as the oxygen-deficient species [PMo12O39]3−, is reformulated as [H2PMo12O40]3−.