Formation Of Oxide Thin Films Research Articles

Effects of UV-irradiation on the formation of oxide thin films from chemically modified metal-alkoxides

The effects of UV-irradiation on the properties of ZrO2 and TiO2 gel films prepared from corresponding metal-butoxides modified with acetylacetone (AcAc) or benzoylacetone (BzAc) have been studied. It was found that the chelate bonds of β-diketones remaining in the gel films were dissociated by the UV-irradiation. The UV-irradiation also changed the properties of the gel films such as solubility; the solubility in acidic solutions was decreased for ZrO2 gel films modified with AcAc and TiO2 gel films modified with BzAc became insoluble in alcohol. Based on these findings, a new fine-patterning process has been established, which enables us to make fine-patterns of ZrO2 and TiO2 films on a variety of substrates.

Development of an Atomic Oxygen Source for Thin Oxide Film Formation

ABSTRACTAtomic oxygen promotes the oxidation of thin films. The authors developed a silent discharge type atomic oxygen source for thin oxide film formation. The atomic oxygen source consists of a quartz discharge tube and two cylindrical electrodes that are attached to the outside wall of the tube. The atomic oxygen concentration is estimated to be 3%.The atomic oxygen source was installed in an ICB (Ionized Cluster Beam) apparatus and applied to the formation of Er-Ba-Cu-0 thin films. By introducing the atomic oxygen during deposition, a film showing superconductivity at 81K was obtained when the substrate temperature was 570ºC. Also the substrate temperature to obtain a film showing superconductivity at 77K was estimated to be 50 °C lower than that for obtaining superconducting film formation in an atmosphere of 6% ozone. The atomic oxygen source was also applied to SrTiO3 thin film formation. Electrical properties of this film were examined and compared with those of films prepared in an atmosphere of 6% ozone. The dielectric constant of SrTiO3 film was improved from 60 to 180 by introducing atomic oxygen instead of 6% ozone. Therefore the atomic oxygen source was proven to be advantageous for thin oxide film formation.

酸化膜作成用小型イオン源の試作 （ＩＩ）

酸化膜作成用小型イオン源の試作 （ＩＩ）

偏光反射解析法による金属の不働態皮膜の観察

The ellipsometric investigation of passivation film on metal was demonstrated. The following topics were described.(1) The passive film on cobalt, to which the ellipsometry was applied for the study of its layered structure in combination with an electrochemical method.(2) The passive film on titanium, to which a multiple-angle-of-incidence “ex-situ” method was applied, combined with the conventional “in-situ” ellipsometry, for surveying the optical constants of titanium substrate as well as the passive film.(3) The thin oxide film formation during the dry corrosion of pure iron.(4) The spectroscopic measurement, from which the optical absorption coefficients of thin passive films on iron and titanium were estimated to be compared with the conventional absorption spectra of the oxides.(5) The recent application of the microscopic ellipsometry to a two-phase stainless steel, the results of which indicated that there was a significant scatter of the film thickness depending on the composition of grains.

酸化膜作成用小型イオン源の試作

酸化膜作成用小型イオン源の試作

Electrical characteristics of Cu-Cu2O diodes fabricated by anodic oxidation

The anodic oxidation of copper in a copper sulphate bath has been performed. From gravimetric measurements of the thickness of the cuprous oxide layer formed, it is observed that the growth law for anodic oxide thin film formation is a power law. The cuprous oxide diodes fabricated by the above technique have been studied using current-voltage and capacitance-voltage methods. From these it is inferred that the resulting device is characteristic of a metal-insulator-semiconductor (MIS) diode.

The identification and characterisation of mixed oxidation states at oxidised titanium surfaces by analysis of X-ray photoelectron spectra

The interaction of oxygen with titanium has been studied by X-ray photoelectron spectroscopy. Methods for analysing composite photoelectron spectra (curve fitting, deconvolution and spectral subtraction) are discussed and examined critically and the advantages of the ‘difference spectra’ approach highlighted. Evidence for variable oxidation states (suboxides) is obtained from an analysis of the Ti(2p) spectra observed during the formation of thin oxide films (ca. 10 A). Angular-dependent studies established that the lower oxidation states Ti2+ and Ti3+ were formed preferentially at the metal–oxide interface, whereas Ti4+ species were dominant at the oxide–gas interface. The distribution of the oxidation states within the thin oxide overlayer may be altered by thermally induced diffusion of Ti0 species from the metal substrate; the latter can occur at low temperature (ca. 200 K) for the thin oxide film regime investigated.

Low Temperature Surface Cleaning of Silicon and Its Application to Silicon MBE

A low temperature thermal cleaning method for Si molecular beam epitaxy (MBE) is proposed. This method consists of wet chemical treatment to eliminate carbon contaminants on Si substrates, thin oxide film formation to protect the clean Si surface from contamination during processing before MBE growth, and desorption of the thin oxide film under UHV. The passivative oxide can be removed at temperatures below 800°C. It is confirmed that Si epitaxial growth can take place on substrates cleaned by this method and that high quality Si layers with dislocations of fewer than 100/cm2 and high mobility comparable to good bulk materials are formed. Surface cleanliness, the nature of thin passivative oxide films, and cleaning processes are also studied by using such surface analytic methods as Auger electron spectroscopy, reflection high energy electron diffraction, and x‐ray photoelectron spectroscopy.

Passivation kinetics of zircalloy-4 electrode in mineral acids under potentiodynamic conditions

The E/ I response of a zircalloy-4 electrode in mineral acids is examined at room temperature under potentiodynamic conditions. On electrodes that have been mechanically polished and cathodically polarized, growth of the oxide phase, ZrO 2, follows the formalism of the Cabrera-Mott model of high field assisted formation of thin oxide films. It is possible to propose a reaction model based on the potentiodynamic experimental parameters, in which the rate determining step is attributed to ionic transfer at the metal-oxide interface.

Formation of Thin Oxide Films at Platinum Anodes in Alkaline Solutions: III . pH Dependence

The kinetics of growth of thin anodic oxide films at platinum electrodes is studied in alkaline solutions of different pH. At all pH's, kinetics above 1.0Vvs. RHE follow the formalism of the high field assisted formation and migration of ions through an oxide film, i.e., , where c is a constant independent of pH, and is the thickness of the film, modified by the thickness of the inner Helmholtz layer, expressed as charge density. is pH dependent; it decreases 60 mV as pH increases one unit. However, the exchange current density, , decreases by one order of magnitude as pH decreases one unit. The dependence of on pH is unexpected for the high field model of growth with either a process at the metal/ oxide film interface, or a process within the oxide phase as the rate‐determining step. It can be explained only if a process at the oxide film/solution interface is rate determining. It is shown that in acid solution, too, this process is rate determining and not a process at the metal/oxide film interface as previously concluded. The observed difference in the activation energies for the growth in acid (25 kcal/mol) and alkaline (18.5 kcal/mol) solutions, which previously could not be accounted for, is due to different species reacting in the rate‐determining step. In acid and neutral solutions, and in alkaline solutions, OH− are the reacting species in the rate‐determining step.

Anodic oxide films at nickel electrodes in alkaline solutions—I. Kinetics of growth of the β-Ni(OH) 2 phase

The growth kinetics of thin anodic oxide films at nickel electrodes are examined in 0.1 N KOH solutions at room temperature under potentiodynamic and galvanostatic conditions. At electrodes that have been mechanically polished and cathodically reduced, growth of the lower oxidation state phase, β-Ni(OH) 2, follows, under both experimental conditions, the formalism of the Cabrera—Mott model of high field assisted formation of thin oxide films. At 10 −3 Acm −2, the field within the oxide phase is 8.5 × 10 6 V/cm. The field decreases 1.3 × 10 6 V/cm for each ten-fold decrease of current density. The potential at which β-Ni(OH) 2 begins to grow, V 0 = −0.39 V vs she, is identified as the reversible potential of the phase. It is, however, 270 mV positive than the reversible potential listed in literature for Ni(OH) 2 formation in solutions of the same pH. It is suggested that the observed reversible potential refers to the β-Ni(OH) 2 phase. The exchange current density for the oxide film growth is 2.3 × 10 −10 Acm −2. Comparison of the kinetics at Pt and Ni electrodes indicates that the activation energy for the growth of the β-Ni(OH) 2 phase is 21 kcal/mole.

An investigation of anodic film formation on electrodeposited ruthenium by potential sweep techniques

Potential sweep techniques were used to investigate the anodic behaviour of reduced ruthenium surfaces, prepared by electrodeposition on gold-plated substrates, as a function of sweep rate, temperature and pH. The most important factor appeared to be pH as this strongly influenced the oxide layer thickness and both the number and location of the peaks on the voltammogram. The formation of thin oxide films on ruthenium at intermediate pH values (3.5–9.5) is attributed to the growth of a compact amorphous film with significant metal-oxygen-metal bridging in the structure. Heavier oxide growth in strong acid is attributed to protonation of the oxide lattice resulting in the formation of a more porous anodic film. Thicker oxide growth in strong base is attributed to the growth of a higher (+6) oxide under these conditions. The effects of both sweep rate and temperature on anodic behaviour in strong acid are attributed to activation-controlled rearrangement of the oxide film.

Formation of Thin Oxide Films of Silicon by Gas Plasma

Formation of Thin Oxide Films of Silicon by Gas Plasma

A method of formation of thin oxide films on silicon in a microwave magnetoactive oxygen plasma

A method of formation of thin oxide films on silicon in a microwave magnetoactive oxygen plasma

Closure to “Discussion of ‘The Kinetics of Thin Oxide Film Formation on Iron Using Proton‐Impact‐Excited X‐Ray Analysis’ [P. B. Needham, Jr., H. W. Leavenworth, Jr., and T. J. Driscoll (pp. 778–783 Vol. 120, No. 6)

not Available.

Discussion of “The Kinetics of Thin Oxide Film Formation on Iron Using Proton‐Impact‐Excited X‐Ray Analysis” [P. B. Needham, Jr., H. W. Leavenworth, Jr., and T. J. Driscoll (pp. 778–783 Vol. 120, No. 6)

not Available.

The formation of thin oxide films on metals

It is shown that one may not expect simple rate laws between the limiting case (i) of transport of ions across a thin oxide film by virtue of an electrical field due to electrical charges of opposite sign at the metal/oxide and the oxide/gas interface and the limiting case (ii) of diffusion of ions and electrons across a thick oxide layer in accord with classical diffusion equations.

Oxygen adsorption, reconstruction, and thin oxide film formation on clean metal surfaces: Ni, Fe, W and Mo

A kinetic investigation is reported of the interaction of molecular oxygen with nickel, iron, tungsten and molybdenum films deposited in ultra-high vacua, covering the pressure range 10 −9 to 10 −3 torr, and temperatures between 77 and 373°K. On each of the metals and under all conditions examined the sticking probability s for oxygen on the clean surface was found to be very close to unity (> 0.99). The sticking probability-coverage profile for nickel shows a minimum at one quarter of a monolayer, which is more pronounced at higher temperatures, and is associated with a phase change of the adsorbate: up to this coverage oxygen is non-dissociatively bound on the surface. Adsorption on the high-coverage phase proceeds with a higher value of s, whence the minimum in the s-profile. At a monolayer coverage s drops to < 10 −4 before a slow process sets in, involving a further substantial uptake of oxygen: the rate of this process is independent of temperature in the range 195 to 290°K, and proportional to the pressure. On iron, only a monolayer uptake is obtained at temperatures < 190° K, but at room temperature the equivalent of 3 monolayers are sorbed when s has fallen to 10 −4. Five distinguishable and reproducible stages are noted in the s-profile, the discontinuities being associated with phase changes in the surface layer. The final stage of the process has an activation energy of 20 ± 5 kcal mole , and the rate is proportional to the pressure ( P < 10 −4 torr). Four stages are noted in the adsorption of oxygen on tungsten and molybdenum films; the final stage on tungsten has an activation energy of 5 kcal mole , and the rate is again proportional to the pressure ( P < 10 −3 torr). About 2 monolayers are taken up at room temperature before s falls to 10 −7. Desorption spectra are obtained to characterise low adsorption heat states on these films. In all cases the populations in these y states are low by comparison with, for example, those found for nitrogen on tungsten 24,25 or titanium 21).

The oxidation of iron-carbon alloys at low temperatures

The formation of thin oxide films (<1000 A) on polished iron-carbon alloys in the temperature range of 200–350°C and in 100 Torr of dry oxygen was investigated. A combination of vacuum microbalance and transmission electron microscopy techniques were employed to characterize the oxidation process kinetically and morphologically, respectively. The initial oxide formation on the iron-carbon alloys obeyed a two-stage logarithmic kinetic mechanism with activation energies of 0.26 eV and 0.32 eV for the first and second stage, respectively. These kinetics and activation energies are in agreement with the two-stage logarithmic kinetic theory developed by Uhlig, assuming electron transfer as the rate-controlling mechanism. Logarithmic kinetics were followed by parabolic kinetics with an activation energy of 1.08 eV, indicating cationic grain boundary diffusion as the rate controlling mechanism. The oxide formed over the iron-carbon alloys at 300°C was primarily due to the oxidation of the ferrite phase, but a thin protective oxide film (~ 150 A) was formed on the carbide phase. At later stages, a lateral growth of the oxide crystallites formed over the ferrite phase resulted in a gradual coverage of the carbide phase. This lateral growth was the major effect of the second phase on the oxidation of two-phase iron-carbon alloys. A systematic study of the effect of the phase boundary length on the oxidation of iron-carbon alloys was quantitatively evaluated.

金属表面における薄いアノード酸化皮膜成長過程の速度論的研究方法に対する寄与―ニッケル不働態皮膜成長の速度論

金属表面における薄いアノード酸化皮膜成長過程の速度論的研究方法に対する寄与―ニッケル不働態皮膜成長の速度論