Phase transitions and structures of organic ultra-thin films have been investigated from temperature dependence measurements of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) using both Langmuir-Blodgett (LB) films and a Mn-arachidate salt powder. DSC revealed that, unlike pure arachidic acid, the Mn-arachidate powder showed two-phase transitions, i.e., the main transition and a new transition or pretransition. XRD of the LB films confirmed the two-phase transitions, and elucidated three phases, namely, a lamellar phase with a certain tilt, a lamellar phase without tilt, and an ordered fluid phase with melted alkyl-chains. These findings indicate that the phase behavior plays a key role in the fabrication mechanics of LB films of transition metal-fatty acid salt, such as the temperature control during the monolayer formation and the annealing processes.
We have studied deposition of hydrogenated Si cluster ions, SinHx+ grown in an External Quadrupole Static attraction Ion Trap (EQSIT), on Si surfaces. The Si6H13+ and Si8H19+ ions, which have sp3 bonding networks, were grown stably in the EQSIT and subsequently deposited on the Si(111)-(7×7) surfaces with impact energy Ed = 6 and 12 ± 1 eV. The surface structures with the clusters were observed by Scanning Tunneling Microscopy (STM) and investigated in comparsion with the Si6H13+ and Si8H19+ structures calculated using the density functional theory. The STM observations indicated that the cluster ions adsorbed preferentially on the faulted half of the Si(111)-(7×7) unit cell. We observed that Si6H13+ is more resistant to fragmentation than Si8H19+ on impact to the surfaces. We consider that the difference is due to the structural difference of the clusters; Si6H13+ ions have a tightly connected ring structure while Si8H19+ ions have chain structures with several isomers.
Photochemical cleaning processes of atmospherically contaminated chromium surfaces have been examined by contact angles of water and by time-of-flight secondary ion mass spectroscopy. Exposure of the contaminated surfaces, where contact angles are uniform, to vacuum-ultraviolet radiation results in characteristic distribution of contact angles before all the portions of the plate surface become hydrophilic. The unclean region which has larger contact angle as compared to the averaged value on the plate shows larger intensity of carbon-containing fragments in the spectrum. In order to explain the apparent discrepancy in these results, a model is proposed in which alternate lateral and normal growth of atmospheric clusters occurs on the chromium surface.
We clarified the atomic and electronic structures of misfit dislocations generated at InAs/GaAs(110) heterointerface by first-principles calculations, and also investigated the behavior of the misfit dislocations during heteroepitaxies, using elastic continuum theory. Our first-principles calculations indicate that the dislocation core has asymmetric five-fold coordinated In atoms, which originate from the charge transfer at the heterointerface. In order to investigate the heteroepitaxial growth mode, we formulated the free energy of the heterointerface system. It was found that the formulation could describe the heteroepitaxial growth mode when some physical parameters were determined appropriately. These parameters are successfully determined by combining the first-principles calculations and elastic continuum theory via total energies of the system. As a result, we found that the formation energy of 90o misfit dislocation was 0.96 eV/Å, and also that the growth mode determined by our theory using these parameters reproduced the growth mode observed by STM studies.
Metallic microstructure inspection is essential in assuring long-life operation of steam power stations. In common chemical etching methods for microstructure observation, the etching conditions are not readily specifiable and delicate handling techniques are required. To overcome this difficulty a physical etching method is employed with micro-sputtering technique where an inner-magnet is provided with a portable evacuation system and a movable power supply. A specimen taken from the main Y-shaped steam pipe of a disassembled power plant was etched using this new apparatus and a replica of the pipe surface was observed by optical microscopy. The result of observation was as good as that obtained by the chemical etching performed under the most favorable condition.
Reaction products such as iron oxide and oxyhydroxide are formed on the surfaces of iron and steel by exposing them to air at room temperature for a long time. Microscopic formation processes and the local structure of the reaction products formed on the iron surface were investigated by using XPS, EXAFS and Mössbauer spectroscopy. Angle-resolved measurements of XPS spectra showed that an oxyhydroxide layer covers a native oxide layer formed on the iron surface. Imaging by micro XPS indicated that fine reaction products, which are oxyhydroxides, are heterogeneously formed on the iron surface by exposure to air for a long time. Experimental results by EXAFS and Mössbauer spectroscopy were also shown to discuss the local structure of the reaction products on the iron surface.
The beamline named ‘SORIS’ was constructed at Ritsumeikan SR Center for studying surface and interface structures by photoelectron spectroscopy (PES) and medium energy ion scattering (MEIS). The former provides the information about the electronic structures and the latter makes it possible to determine the atomic configurations of surfaces and interfaces. Two types of varied-space-plane gratings monochromate SR-light in the energy range from 5 up to 700 eV and photoelectrons are detected by a hemispherical energy analyzer with a radius of 139.7 mm. A new toroidal electrostatic analyzer designed and constructed for MEIS has achieved an excellent energy resolution of ΔE/E = 9×10−4 and thus allows a layer-by-layer analysis. Samples are prepared by molecular beam epitaxy with three Knudesn cells. In addition, clean surfaces can be oxidized by using an infrared heating system. The analyses are performed in situ without exposing samples to the air. As typical applications, we show the structural analysis of TiO2-terminated SrTiO3(001) surfaces and the initial oxidation process for the Si(111)-7×7 surface.
Atomistic deformation processes in twin boundaries of gold were demonstrated. Point contacts of gold were produced by the contact between nanometer tips using piezo-driving. The sliding occurs at twin boundaries inside the point contacts during subsequent compression and retraction. The migration of boundary planes, grain rotation and the variation in boundary planes were simultaneously observed. For typical twin boundaries, the relation between the sliding and migration was analyzed. The results were explained based on Coincidence-Site-Lattice and DSC theories.