The scanning tunneling microscope (STM) was invented less than five years ago by G. Binnig and H. Rohrer. In 1986 they were honored with the Nobel prize in physics, together with E. Ruska who invented the transmission electron microscope in 1933. The principles of the STM and the construction of the instruments are described by dividing them into several key technologies: (i) vibration isolation; (ii) course and fine positionings and scannings; (iii) thermal drift, hysteresis, and creep of piezoactuaters; (iv) metal probes; and (v) electronic control circuits. Surface structures recently observed by the STM on metals, semiconductors, etc. are reviewed. The future development of the STM is mentioned very briefly.
Linear-chain organic molecules, calcium stearate and cadmium arachirate, were deposited on pre-evaporated epitaxial films of aluminum in vacuo. The two-layered films of metal and organic were analyzed by transmission electron microscopy and electron diffraction. The molecules lay along the <110> direction of Al (001) surface at a low temperature of substrate, while at a high temperature they stood and took the axis relationship that <110> organic direction becomes parallel to <110>Al. The growth mechanism of MO structure is to be discussed.
Problems in traditional derivation process of Thomson-Freundlich equation are discussed, and modified equations for spherical particle systems are given as follows, RT ln (pr/p∞)=(3Vεs/r) and RT ln (Xr/X∞)=(3Vεi/r) Where, p: vapour pressure, X: solubility expressed in mole fraction of the material in the solution, r: particle radius, V: molar volume, εs: surface free energy of the particle and εi: interface free energy between solution and the particle. The subscripts r and ∞ attached to p and X mean those values being in equilibrium with r=r and r=∞. The molar surface or interface free energy can be used instead of (3 Vεs/r) and (3 Vεi/r) for a crystalline particle having its own stable crystal habit.
The oxygen sorptive and catalytic properties of Mn-based perovskite-type oxides were investigated and compared with those of Co-based oxides. La1-xSrxMnO3 could be classified in two groups according to both the profiles of TPD chromatograms of oxygen and the defect structure. The first group (x=0 and 0.2) showed a large desorption peak centered at ca. 700°C (high-temperature peak). It was proposed that in these systems cation vacancies associated with the formation of Mn4+ were incorporated into the crystal lattice to mitigate the static Jahn-Teller distortion of Mn3+ at low temperatures and that on heating the vacancies were eliminated while giving rise to the oxygen desorption. On the other hand, the second group (x=0.4-1.0) were almost stoichiometric and it showed a small and plateau-like oxygen desorption peak below 500°C (low-temperature peak). The catalytic activities of La1-xSrxMnO3 were found to increase with increasing x and to reach a maximum at x=0.8. This trend coincided with that of the amounts of oxygen desorbed in the region of low-temperature peak. It is inferred that La1-xSrxCoO3 catalyzes oxidation reactions by “intrafacial” mechanism, in which oxygen vacancies in the bulk play an important role, while La1-xSrxMnO3 does by “suprafacial” mechanism, in which surface oxygen plays dominant roles. In La1-xSrxMn1-yCoyO3, the amounts of desorbed oxygen increased monotonously with increasing y while the catalytic activity reached a maximum at a value of y.
Cu or α-Cu-Zn dendrites which show the shape of pentamerous flower exhibiting fivefold symmetry are grown by zinc reduction of CuBr at 600°C or thereabouts. Since the morphology of dendrites reflects the symmetry of the growth axis, the growth axis is considered to be a fivefold rotation axis. The size of large dendrites reaches 120 μm. Such a large metallic crystal exhibiting fivefold symmetry in the morphology has not been observed.
After a brief explanation of bulk amorphous semiconductors, the surfaces of hydrogenated amorphous silicon films a-Si: H are to be discussed. In a-Si: H, surfaces are usually covered by atomic hydrogens bonded to Si. Therefore oxidization is much slower when compared with crystalline silicon. The surface states and adsobates that induce the space change region are about 0.3 to 0.5 μm. The effects of adsobates such as H2O, NH3, (CH3)2O, O2 and Se are to be discussed.
The membrane potential distributions and the dynamic changes of two day old bean roots under gravistimulation were shown by glass-micro electrode techniques. The electrodes held by three dimensional hydraulic micro-drives were strictly inserted into elongating cortical cells. Membrane potentials, root inclinations and the position of the cortical cells were measured simultaneously. Gravistimulus electrogenic components were distribute in the elongating region and these electric distributions were reconstituted within 30sec of the gravistimulation changes. The reconstitution was more rapid than the hormonal translations.