Observation of cleaved GaAs (110) surfaces is performed by scanning tunneling microscopy in ultrahigh vacuum. Monoatomic steps and anomalously large corrugation regions of a few tens of square angstroms in the atomically flat terrace are observed. Since the number of the large corrugations corresponds to the number of the dopant within a few atomic layers, these corrugation regions are probably induced by the dopant. Voltage-dependent morphology, which originates from the local density of states of each constituent at the surface, is also discussed.
Silver tripolyphosphate films were formed on slightly cathodically polarized silver electrodes in aqueous solutions containing Ag+ and tripolyphosphate ions. The solutions were kept supersaturated with silver tripolyphosphate during the film formation. The potential of the silver electrode, on which the silver tripolyphosphate film was formed at a very low current density, showed a linear relationship to the tripolyphosphate ion concentration between 10-4 M and 10-1 M.
Chemical activity of fresh aluminum surfaces were investigated by a newly developed method. Pressure decrease owing to chemisorption of organic compounds were monitored by a quadrupole mass spectrometer. The adsorption activity of organic compounds increased as in an order of ethers<alcohols<carbonyl compounds. Benzene and 1-hexene which have ic-electrons exhibited no chemical activity to fresh aluminum surfaces. Hydrogen evolution due to decomposition of chemisorbed molecules was observed during scratching. The desorption rate increased linearly with adsorption rate excepted for water. A large amount of hydrogen was produced from adsorbed water molecules during scratching. Reactivity of ROR' type compounds on fresh aluminum surface was ranked as follows: ethers<alcohols<water.
Effects of high dose carbon implantation on the anodic dissolution behaviour of iron surface layers have been studied by multi-sweep cyclic voltammetry (CVM) in an acetate buffer solution of pH 5.0. Implantation of 12C+ was performed with doses of 2×1017-1×1018 ions/cm2 at an energy of 100keV, and at a nearly room temperature. XPS, XRD and laser Raman spectroscopy were used to analyze the composition and structure, before and after CVM measurements. High dose carbon implantation was extremely effective in suppression of the anodic dissolution of iron. The carbon depth profile showed a gaussian-like shape even at the highest dose, as predicted by the LSS theory, in which the carbon was combined with not only iron but also carbon itself. After CVM measurements, a glassy carbon film, including the graphite and disordered-graphite structures, was found on the surface. From the results, it is concluded that iron carbides and the carbon film formed by high dose carbon implantation and electrochemical treatment are effective in corrosion protection of iron surface layers.
Small-signal AC resistance and DC resistance of evaporated pure Al interconnection were measured under the DC current stress which envokes electromigration. AC resistance weakly depends on frequency and increases as the frequency is lowered. This is compared with the fluctuation phenomenon in thin metal films which has been observed in flicker noise studies. Time dependent resistance change can be analized by the model of nucleation and growth of the voids in a metal film. Observed drop and preceding oscillaion in resistance can be interpreted as the evidence of the condensation of void nuclei and their phase transition into a macroscopic void.
Recently two phenomena concerning the instability of Prototypes of Kilogram have been disclosed by gravimetric technique ; one is the change in the mass related to the ambient relative humidity and the other is the noticeable mass increase lasting about a year after cleaning. To elucidate these phenomena atomically, surface analyses such as FT-IR and XPS were made. For the former phenomenon, even under a vacuum of 10-2 Pa, the order of the -OH peak values for pure Al. Pt and Au was in agreement with that of weight gain of these metals. For the latter, it was clarified that about 50% organic carbon was removed during supersonic cleaning in solvents, and that the surfaces are covered once again in 6 hours. The mass changes by cleaning were estimated about 10 μg in the case of the Prototype.
Thermal decomposition of cycloparaffins (C5-C8) and normalparaflins (C5-C8) on a clean stepped Ni (755) surface was investigated by low-energy electron diffraction (LEED). Auger electron spec-troscopy (AES) and temperature programmed desorption (TPD). Hydrocarbons were exposed on the surface at 123 K, No ordered LEED pattern was observed for all hydrocarbons. These molecules decomposed completely on the surface and remained as surface carbon while heating up to 573 K. No other species than hydrogen and reactant hydrocarbons was observed during TPD measurement. The initial decomposition probabilities of hydrocarbons except cyclopentane depended solely on the desorption temperature of monolayer adsorption state of hydrocardons irrespective of the number of carbons or types of hydrocarbons, i. e., cyclo or normal.
Replicas for TEM observation are made with the films plasma-polymerized by a recently developed discharge glow method. The replicas allow visualization of the surface pressure-area curve, demonstrating numerous images of a monomolecular layer transferred from an aqueous subphase onto a glass plate at various surface pressures. The TEM technique is expected to assist preparation of the so-called Langmuir-Blodgett (LB) film without any extra structural defects on the electron microscopic scale. The method enables us to obtain some informations on normalizing the film properties for the practical use of them. We exemplify the normalization for a NO2-responsible monolayer of amphiphilic phthalocyanine with a smooth surface produced by a subphase-lowering technique developed previously.
Growth of tin oxide films on glass substrates from the solution of several organotin compounds, (C4H9)4Sn, (C4H9)3SnOOCCH3, (C4H9)2Sn(OOCCH3)2, (C4H9)3SnCl and (C4H9)2SnCl2, by spray pyrolysis has been found to be possible. Of these compounds, only the crystallinity of the tin oxide film grown from (C4H9)2SnCl2 was affected by annealing at 600°C after being prepared at 400°C. The texture coefficient of the tin oxide films determined from XRD profiles showed that preferred orientation of the films were different depending on the source compounds. The crystallite size of the tin oxide films was also discussed in terms of the growth parameters. Furthermore, it has been proved that the films grown from the Cl-free compounds were of smooth surfaces.
An experimental approach is presented for a quantitative determination of the mixing ratio of two different polymers having the same molecular chain. The method is based on the measurement of the relative intensities of C-H bond signals reflecting the electronic structure of valence band. Usefulness of this treatment is confirmed for the sample of polyethylene/polypropylene mixture.
Scanning tunneling microscopy has been used to investigate the site of domain boundary on Si (111) 7×7. Within a 0.4μm×0.4μm area, six domain boundaries are observed, and all of them are located at the terraces constricted by zig-zag steps. From the step configuration, the observed surface is defined as a vicinal (111) misoriented by 0.40°towards . Discussion is focused on the shape of the vicinal (111) surface and the effect of the domain boundary on the step configuration.
An advanced hot filament chemical vapor deposition method was developed to make it possible to control the substrate temperature regardless of other CVD parameters (e. g. filament temperature and filament-to-substrate distance). Independent and accurate control of the substrate temperature was achieved by resistive heating of the substrate with electric current through the substrate itself and also by noncontact optical monitoring of the substrate temperature. By employing this method, the growth rates of diamond films were measured as functions of the substrate temperature and the filament-to-substrate distance.
Rhodamine 6 G doped alumina film was prepared by sol-gel process. Triton X-100 or β-cyclodextrin was added to the doped film to improve its photo-properties. For the laser action by pumping with a N2 laser, Triton X-100 improved the emissibility and β-cyclodextrin prevented the photo-bleaching.