No abstract

No abstract

ZnO film was prepared from 0.1moldm−3 zinc nitrate aqueous solution by the potentiostatic technique using a three-electrode system at 313–343K . The ZnO film was characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, measurements of interface pH and electrochemical quartz crystal microbalance (EQCM) during the electrodeposition were carried out to elucidate the deposition mechanism. It was disclosed that the deposition scheme at the initial stage is quite different depending on bath temperature. The change in deposition mechanism with temperature is closely related to the increased thermodynamic stability of ZnO at high temperature. Based on EQCM analysis, it was suggested that the precursor of ZnO is slowly transformed to ZnO at low temperature, but the formation of ZnO is extremely rapid at high temperature, i.e., ZnO directly deposits at high temperature. Auger analysis indicated that transition from the precursor to ZnO crystal started from the bottom to the surface when the amount of precursor became larger than a critical value depending on temperature.

Ag nanoparticle catalysts were prepared to replace the Pd/Sn catalysts for electroless Cu plating. Suspensions of Ag nanoparticles, of which the average diameter was 4.6 nm, were obtained instantaneously by mixing a AgNO3 solution and a Sn(II)–citrate complex solution at a nearly neutral pH. The composition and electron diffraction patterns of the nanoparticle as well as a high stability of the suspensions suggested that the nanoparticles have the core-shell structure composed of the metallic Ag core surrounded by the SnO2 shell. The adsorption of Ag nanoparticles onto the epoxy substrates was promoted by conditioning the substrate with alkyltrimethylammonium chloride (ATA) having an alkyl tail longer than C16. A small amount of Sn was also adsorbed. The promotion of the Ag nanoparticle adsorption can be accounted for by the large amount of adsorbed surfactant due to the hydrophobic interaction with the substrate. The positively charged ATA adsorbates acted as an electrostatic glue to adsorb the negatively charged Ag nanoparticles. Electroless Cu deposition was started at the epoxy substrates catalyzed with Ag nanoparticles.

In the chemical ZnO deposition on Pd-catalyzed glass from aqueous dimethylamineborane ͑DMAB͒ solutions, effects of counteranions ͑NO 3 − , Cl − , ClO 4 − , and SO 4 2− ͒ and dissolved oxygen ͑DO͒ on the hydrolysis behavior of Zn 2+ and the growth regime of ZnO were studied using sodium and zinc salt solutions bubbled with O 2 , air, or Ar gas. The interaction of the counteranions with H + and Pd as well as Zn 2+ was suggested as an important factor for the chemical ZnO deposition, and it was found that only NO 3 − can raise the pH of a DMAB solution without DO, affording the continuous ZnO growth. Dissolved oxygen accelerated the ZnO nucleation process on the Pd and had less influence comparable to NO 3 − on the subsequent growth on the ZnO surface. The ZnO films deposited from Zn͑NO 3 ͒ 2-DMAB solutions bubbled with O 2 , air, or Ar gas were characterized with an X-ray diffractometer, field emission scanning electron microscope, UV-visible spectrophotometer, and Hall coefficient analyzer. The Ar-bubbled solution gave superior ZnO films in terms of crystallinity, growth orientation, surface morphology, and electrical conductivity due to the relatively moderate crystal nucleation compared to in the presence of DO.