The curve synthesis method based on the non-linear least-squares fitting was applied to the quantitative analysis of Auger electron spectroscopy. The characteristics of the present method are that it pemits the automatical correction of energy deviation between reference and observed spectra and thus the fit becomes better than in the usual least-squares treatment. Examples using an alloy surface show that the present mehtod is useful even in the case that the conventional method of measurement of peak-to-peak values was unsuccessful. Furthermore, the development of a universal method for the analysis of Auger data was discussed.
The intensity oscillation of reflection high-energy electron diffraction was observed during the growth of AlxGa1-xAs accompanying the incorporation of As into an Al and Ga mixed layer on a GaAs substrate. The degree of oscillation depends on the Al fraction of the mixed layer and on the substrate temperature. Incorporation of As into Al on an AlAs surface was also investigated to compare with the case of As incorporation into the mixed layer on the GaAs substrate. It was found that mixing of Ga in the Al metal layer strongly lowered the low-temperature limit of the intensity oscillation and also increased the oscillation magnitude. This will be attributed to a large migration of Ga atoms rather than Al atoms.
Mn-ferrite films were obtained in atmosphere by the heat treatment of film samples which is prepared by evaporation from Fe-Mn-Bi source. There was tries to clarify its relation to microscopic structure and magnetic properties in terms of the formative process of Mn-ferrite thin films. The qualitative and quantitative analysis of Mn-ferrite was made measurements by X-ray diffractometer method and the chemical effect in the low energy Auger spectrum, respectively. The prepared films showed perpendicular magnetic anisotropy. The saturation magnetization (4πMs), remanent magnetization (4πMr⊥), coercive force (Hc⊥) and anisotropy field (Hk) were 4.4 (kG), 0.6 (kG), 350 (Oe), and 1.5 (kOe), respectively. The cause for the perpendicular anisotropy is attributed to the effects of the perpendicular configuration of column grains in the films and of induced magnetic annealing effect.
The effects of molecular beam flux and substrate temperature on the MBE growth rate of ZnSe are studied. It is found that, at relatively high substrate temperatures, the growth rate is influenced by the desorption and adsorption of Se and Zn atoms. The reduction of growth rate results from Se atom desorption, Zn atom desorption, and both Zn and Se atoms desorption at flux rations, JZn/JSe>1, <1, and ≅1, respectively. The activation energy values are 1.2eV for the desorption of Zn atoms and 0.86eV for the desorption of Se atoms. Three MBE growth models were applied to explain the present results. A model considering the desorption of Zn and Se atoms from precursor states is proposed in this paper and it can best explain the relationship between the growth rate and the substrate temperature or the flux ratio.
The effect of a low temperature plasma treatment on the surface properties of polymethylmethacrylate (PMMA) was investigated. The adhesion strength of MgF2 thin film deposited on the treated surfaces was studied in detail. PMMA substrates were treated in an rf (13.56MHz) plasma reactor, then MgF2 thin film was physically deposited on the treated PMMA substrates. The experiment was carried out for 4 types of source gases, O2, N2, Ar, and H2. The adhesion strength of MgF2 thin film was measured by means of a topple test. The adhesion strength increased significantly after a few minute plasma treatment, particularly with O2 source gas. The formation of oxgen containing groups on the treated PMMA surface was identified by XPS analysis. The decrease of the water contact angle (θ) on the treated surface was also observed, and the adhesion strength was proportional to cos θ. The additional treatment decreased the adhesion strength in spite of the increase in cos θ. It is identified by XPS analysis that a weak layer is formed just below the surface of additionally treated PMMA. This may be caused by the damage on the main chain of PMMA by UV radiation during the treatment.
The nondestructive depth profiling of molecular state of zinc phosphate coatings on iron has been made by using infrared photoacoustic spectroscopy. The advantages of this spectroscopy are : (1) the escape depth of photoacoustic signals can be varied with different measuring parameters; (2) highly light-scattering materials and powdered samples are also measurable, and (3) the sample surface area required for the measurements is relatively small. Distinctive five peaks in the photoacoustic spectrum are assigned to phosphate ions and the coordinated water molecules. The escape depth of signal is estimated as about 2.2 micrometers for this sample system but it is possible to make the escape depths longer by impinging primary beams modulated with lower frequencies. TO and LO splitting of phosphate ion vibration is observed with the thin coating layer. Coordinated water is deficient in the region adjacent to metal and substrate interface in comparison to the outer layer of the coatings. Chemical composition and structure at the interface are briefly discussed.
Electrical properties of SiC sintered with 0.34wt%6.89wt% boron nitride and 2.0wt% carbon in the temperature range of 1900°C2100°C for 30min in vacuum were investigated. Specimens containing 1.15wt% boron nitride (0.5t% boron) showed the most remarkable densification independent of the sintering temperature. The electrical conductivity of specimens containing 1.15wt% boron nitride was the lowest, and the value depended strongly on the frequency and measuring temperature. In order to explain the experimental results, a microstructure model, charge distribution model and energy band model were proposed. The electrical conduction mechanism was discussed based on these models.
Pb/Si (111) surface superstructures have been studied using reflection high energy electron diffraction (RHEED) and molecular beam deposition techniques. The dependences of Pb/Si (111) surface structures on the Pb coverage and on the substrate temperature were elucidated on the basis of the RHEED observation in the coverage range from 0ML to 2ML and in the temperature range from 30°C to 500°C. In addition, we have measured changes in the RHEED intensities during Pb deposition. The results of the RHEED intensity measurements show that the saturation coverage for √3×√3 (α) and √3×√3 (β) superstructures are 4/3ML and 1/3ML, respectively.
The early growth stages of GaAs films grown on GaP (100) substrates by MBE have been studied by Angle-Resolved XPS. From the results of quantitative analysis of the components of the GaAs/GaP surfaces, it was concluded that the GaAs films grew in the Stranski-Krastanov growth mode.
Co-Mn Conposite oxide films were formed on stainless steel electrodes by polarizing them slightly cathodically in a dilute aqueous solution containing Co2÷ and MnO4- ions. The solutions were supersaturated with sparingly soluble compounds, Co2O3 and MnO2, which were produced as a result of the redox reaction between Co2+ and MnO4- ions. Supersaturation was kept during the film formation. The [Mn] / [Co] ratio of the films varied with the concentrations of Co2+ and MnO4- ions in the solution, the elapsed time from solution preparation, and the electrode potential of stainless steel. This method is applicable to the film formation of sparingly soluble compounds on conductive materials.
Epitaxial layers of ZnTe were grown on (100) GaAs substrates by metalorganic chemical-vapour-deposition using dimethylzinc (DMZn) and dimethyltelluride (DMTe) as alkyl sources. The DMTe source was precracked because its high pyrolysis temperature is as high as 500°C. The grown layers have been characterized by using scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy and 4.2K PL techniques. It is shown that the photo-luminescence spectra of ZnTe epilayers depend upon (DMTe) / (DMZn) concentration ratio and upon the substrate temperature.
The weight change of WO3 electrodes and the response time of coloring reactions were measured as a function of the number of coloring-bleaching cycles. The results obtained by weight measurements in situ by using a liquid phase quartz crystal microbalance implied that the water incorporated into the WO3 films at the initial several cycles contributed to the aging effects of the coloring response.
In order to understand basic tribological processes of materials, it is important to characterize the surface structures and to measure the surface processes in situ. The importance of surface science in tribology is discussed by introducing the studies at the Surface Science Branch of NASA Lewis Research Center.