Junichi Katayama

Characterization of Boron‐Incorporated Zinc Oxide Film Chemically Prepared from an Aqueous Solution

Boron-incorporated ZnO film which had a wurtzite structure and showed optical bandgap energy of 3.3 eV was prepared chemically onto a nonconductive substrate by immersing the substrate in an aqueous solution containing a zinc nitrate and dimethylamineborane (DMAB) at 333 K. Effects of the incorporated boron on the structural, optical, and electrical characteristics of ZnO film were investigated using X-ray diffraction, evaluation of surface morphology with an atomic force microscope, measurements of optical transmission spectra, and Hall measurement. Small amounts of boron atoms, which originated from the DMAB, were incorporated into ZnO grain and gave the lattice expansion. A pore-free ZnO film with a smooth surface was obtained from the 0. 1 mol/L DMAB solution. The ZnO film showed optical transmission as high as 80% in the visible light region and resistivity of 3.6 × 10 2 Ω cm with carrier concentration of 1.7 × 10 16 cm -3 and mobility of 1.0 cm 2 V -1 s -1 . It was speculated that the incorporated boron atom acted as a donor in the ZnO film.

Effect of bath temperature on the electrodeposition mechanism of zinc oxide film from zinc nitrate solution

ZnO film was prepared from 0.1 mol dm -3 zinc nitrate aqueous solution by the potentiostatic technique using a three-electrode system at 313-343 K. 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 Catalyst for Electroless Cu Deposition and Promotion of Its Adsorption onto Epoxy Substrate

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 AgNO 3 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 SnO 2 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.

Effects of Counteranions and Dissolved Oxygen on Chemical ZnO Deposition from Aqueous Solutions

In the chemical ZnO deposition on Pd-catalyzed glass from aqueous dimethylamineborane (DMAB) solutions, effects of counteranions (NO - 3 , Cl - , ClO - 4 , and SO 2- 4 ) and dissolved oxygen (DO) 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 Zn(NO 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.

New Chemical Solution Process for Fabricating Copper Layer on Zinc Oxide Film

Fabrication of thin layer on a zinc oxide film was performed by a novel ambient temperature chemical solution process. The process consisted of two steps, introduction of ion into film by immersing in an aqueous copper(II) sulfate solution, and reduction of ion to metallic by immersing in an aqueous potassium borohydride solution. The resultant layer showed resistivity of . ©2000 The Electrochemical Society

Chemical Formation of Ohmic Cu Layer on Highly Resistive Cu2O

A metallic Cu layer was chemically formed on an electrodeposited Cu 2 O layer with high resistivity by a simple immersion in aqueous solutions containing either potassium borohydride or dimethylamineborane for several minutes. The structural and electrical characterizations were performed using a X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, four-point probe tester, and current-voltage measurements. A highly adhesive Cu layer was formed on the Cu 2 O under-layer by immersion in both solutions, and the thickness increased with increasing immersion time. The sheet resistance as low as 0.15 Ω and resistivity of 6.6 X 10 -6 Ω cm were obtained for the 0.44 μm thick Cu layer prepared by immersion for 300 s. The Cu layer also showed an ohmic behavior to the Cu 2 O layer.

Effects of P Content of Electroless Ni-P under Layer on Displacement Au Films

無電解Ni-Pめっき上置換Auめっき皮膜の構造とはんだ付け性に及ぼすP含有率の影響をESCA, EDS, SEMそしてメニスコグラフ法を用いて検討した。めっき直後の置換Auめっき皮膜は純Au層と金属状態のNiとAuが混在する層から成り, 良好なはんだ付け性を示した。しかし, 2時間の水蒸気処理を行うことによりAu/Ni-P皮膜上にNi (OH) 2層が形成され, はんだ付け性は著しく低下した。また, はんだ付け性低下の程度はNi-P皮膜のP含有率により異なり, Ni-9.1wt%P/Au皮膜はNi-2.7wt%P/Au皮膜に比べて良好な結果を示した。これは, Ni-P皮膜のP含有率が低下することにより形成されるNi (OH) 2層の厚さが増加するためである。