Ultrathin stoichiometric PbTiO3 films, 10∼100nm thick, were deposited on (001)SrTiO3 and miscut (001)SrTiO3 substrates at 600°C by rf planar magnetron sputtering to understand the microstructure of initial film growth. The electron microscopy and X-ray diffraction analysis suggested the epitaxial growth of (001)PbTiO3/(001)SrTiO3 with three dimensional crystal orientation, however the PbTiO3 films still included crystal boundaries. Deposition on a miscut (001)SrTiO3 substrate under stoichiometric conditions reduced the crystal boundaries and provided continuous ultrathin films of single crystal PbTiO3.
A surface imaging technique using secondary electrons, scanning electron surface microscopy has been applied to investigate the transformation of (7×7) domain boundaries on Si(111) and the effect of domain boundaries on Ge solid phase epitaxy. Rearrangement of the domain boundaries takes place to form stabilized structures by annealing for several minutes at 8°C below the (7×7)-(1×1) transition temperature, Tc. The stabilized boundaries are those in the <110> directions which reflect the shape of the (7×7) unit. This is the result of minimizing the energy of the boundaries, which consist of (1×1) structure fluctuating with the size of (7×7) units at Tc-8°C. Ge deposited on the Si (111) surface at room temperature was observed to form islands initially at the domain boundaries and steps during solid phase epitaxy.
The surface compositions of Pb-Sn and Pb-Sn-Ag alloys were investigated by means of AES and SIMS measurements. The AES spectral intensities obtained under the simultaneous Ar ion sputtering during the analysis showed that the surface lead concentration depleted drastically, whereas it recovered quickly once the Ar ion bombardment was discontinued. The tin concentration, on the other hand, showed a completely opposite tendency to lead. It is shown that this phenomenon can be interpreted as the results of preferential sputtering and diffusion of the lead atoms. The results are also discussed with the Dynamic-SIMS data, which is proved to be consistent with those obtained by the AES measurement.
X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation were applied for the clarification of the surface oxidation behavior of chromium nitride films which were prepared by cathode arc ion plating method. The XPS analysis of the oxidized samples demonstrated that the presence of nitrogen-containing intermediates generated N1s XPS peaks at higher binding energies than that for nitrogen in chromium nitride. In the N K-edge XAS spectra of the oxidized samples, a sharp peak assigned to 1s-π* transition was observed at a higher energy than that for the N2p-Cr3d peak assigned to chromium nitride. The above results indicate that, with replacement of the nitrogen in chromium nitride by oxygen, the released nitrogen occupies the interstitial position in the chromium oxide matrix as molecular or atomic nitrogen. A part of the interstitial nitrogen in the chromium oxide matrix is evolved from the surface with further progress of oxidation. Oxynitride species, described as CrNxOy, are not likely formed during the course of the surface oxidation.
To take the first step toward sharing the X-ray photoelectron spectra obtained by using different types of instruments, characterization of the energy dependence of the intensity scale of the XPS apparatus with the double-pass CMA as an energy analyzer has been made. For the characterization of the apparatus two independent methods were utilized. One is to use the relation between a peak area intensity and a retarding ratio, and the other is to use the 'standard' Auger spectrum in the COMMON DATA PROCESSING SYSTEM as a reference spectrum. In each of the methods, the energy dependence of E-1.0, which corresponds to the calculated value from the principle, was obtained. Therefore, in order to get the energy dependence of the intensity scale of many different instruments, we propose to use the spectra obtained by the apparatus as the 'secondary-standard' XPS spectra in the COMMON DATA PROCESSING SYSTEM.
Initial stage growth and electronic structures of Al overlayer on a wide-terrace single-domain Si(001)2×1 surface has been studied by low-energy-electron-diffraction (LEED) and photoelectron spectroscopy. The sequences of 2D phases found by LEED for Al coverages ≤ 0.5 ML at RT and 300°C are interpreted on the basis of an order-disorder transition of arrays of one-dimensional Al-dimer chains. The detailed electronic structure of 2×2 phase formed at ∼0.5 ML has been studied by angle-resolved photoelectron spectroscopy (ARPES) using synchrotron radiation. The existence and dispersions of five different surface states are identified for the first time, one at binding energies a little less than 1 eV and the others between 1 and 2 eV. The origin of the surface states can be interpreted in terms of the Al-dimer structures on Si(001).
The DV-Xα-Cluster molecular orbital method has been applied to investigate the mechanism of NO adsorption and dissociation at the oxygen vacancy of LaCoO3 perovskite-type oxides. This study has been undertaken in order to design and develop the catalysts with high activities for the NOx direct decomposition. It is indicated by calculation that when NO is adsorbed at the oxygen vacancy of LaCoO3 catalyst, almost half of the 2π* band in the adsorbed NO is occupied with electrons, because of the electron back donation from the catalyst to the 2π* band of adsorbed NO. It is concluded that N-O bond becomes weak as NO adsorbs at the oxygen vacancy of LaCoO3 catalyst at the primary step of NO decomposition.
S(KL2, 3L2, 3) resonant Auger decay processes were studied for mono- and multi-layered CS2 on Cu(100). It has been found for the mono-layer that a spectator Auger peak shifts almost linearly with incident photon energy (hν) and that it merges into a normal Auger peak when hν is adjusted above the Sls absorption. In addition to the similar hν shift of the Auger peak, it has been observed for the multi-layer that the KL2, 3L2, 3 Auger structure is split into a spectator and anormal Auger peaks. The results obtained are explained in connection with the X-ray resonant Raman scattering and the core-hole screening by conduction electrons of the Cu substrate.
Co-Axial Impact Collision Ion Scattering Spectroscopy (CAICISS) was used to determine the change in elemental composition of the GaAs(001) surface at temperatures up to 420°C caused by low energy Ne ion bombardment at doses of up to 1017 atoms/cm2. The as-received GaAs surface was shown to be Garich consistent with the presence of a gallium based natural oxide at the surface. At temperatures of up to 320°C, sputtering the surface to a dose of ∼1016< atoms cm-2 resulted in a As/Ga surface composition ratio close to 1:1 indicative of sputter removal of the oxide layer. Annealing the as received wafer at 630°C in an attempt to remove the natural oxide layer was found to result in a near 100% Ga terminated surface, however, annealing the same sample after prior room temperature sputter removal of the natural oxide layer resulted in a slightly arsenic rich surface.
Molecular orientation of polydiacetylene monolayers formed at the air-water interface was examined by using fluorescent and polarizing microscopes. We found two different directions of polymerization versus the proper crystallization axis of the monolayer domain. We concluded that the relationship between polymerization and crystal growth is the significant factor for the formation of two different kinds of domains having right and left handed spirals.