X-ray reflectometry (XRR) is one of the most powerful techniques to evaluate structures of thin and multilayered film materials. In Japan, certified reference materials of thin film and superlattice have been developed using a SI traceable XRR. In order to realize XRR with SI traceability, establishing an angle calibration system for the goniometer and accurate uncertainty evalutation method were essential. Reflectance correction method using an X-ray tracing technique has been developed in order to reduce uncertainty caused by surface flatness of specimens. Although XRR profiles obtained from the same specimen with different surface flatnesses did not agree, they agreed very well by using reflectance correction. The agreement of fitting results after reflectance correction was comparable to a repeatability of XRR.
Stress evolution during initial stage of Ge nanodot formation on Si(111)-7×7 has been investigated by using simultaneous measurements of the substrate curvature and the surface morphology. In the beginning of the first bilayer growth of Ge on Si(111)-7×7, a strong compressive film stress is observed, indicating a formation of a two-dimensional wetting layer. When the layer thickness approaches the critical one for three-dimensional nanodot nucleation, a clear bend in the stress curve is observed, corresponding to a partial relaxation of the lattice planes on the surface of the nanodots. Moreover, a stress transition has been also found to exist in the very early stage of the nanodot formation, which is concurrent with the trench formation around the three-dimensional nanodots.
We have previously reported that low-degradation XPS depth profiling of a polymer was effectively observed using C60 ion beam sputtering. However, the suitable sputtering condition for C60 ion beam has not been studied in detail yet. In this paper, we would like to discuss the influence of C60 ion beam angle of incidence upon XPS depth profiling for organic polymers. The results obtained are: (1) Relative sputtering yield for SiO2 was increased with the angle of incidence, (2) Carbon residue in the sputtered Si substrate is decreased with the higher angle of incidence (3) Degradation of atomic concentration (C and O concentration) and chemical states for both carbon and oxygen in polyethylene-terephthalate remained relatively intact by using a grazing angle of 75 degree. In conclusion, the higher angle of incidence seems to be better for the XPS depth profiling using C60 ion beam.
We have characterized the adsorption properties of protein molecules on carbon nanotube surfaces by infrared vibration spectroscopy. We observed the vibration modes of protein molecules from the avidin-adsorbed CNTs. Density of the adsorbed avidin molecules was higher on acid-treated CNTs than on non-treated ones. These results indicate that CNTs are suitable materials for an adsorbent of bio-molecules, and are promising for high-sensitivity bio-sensors and removers of toxic proteins.
Tribochemical activation of gold surface is reviewed. When the surface layers such as metal oxides and organic contaminants removed mechanically, nascent surfaces which have defects and dangling bonds are formed. Gold surface was activated by friction in a vacuum chamber, and chemisorption and surface reactions of organic compounds were monitored with a quadrupole mass spectrometer. Gold becomes to be active by mechanical contacts. Compounds such as olefins, aromatics and organic sulfides chemisorbed more easily than polar compounds such as carboxylic acids on the nascent gold surface. Olefins and benzene chemisorbed on nascent gold surface followed by hydrogen evolution as a dehydrogenation product of olefins. The formation rate of hydrogen was proportional to sliding velocity that is formation rate of nascent surface. Hydrogenation of the olefins also observed on nascent gold surface. The dehydrogenation and hydrogenation occurred on nascent gold surface even at room temperature. Surface defects formed by mechanical contacts may act as an active site for the reaction.
The self-spreading behavior of lipid bilayer was investigated using hydrophilic substrates with and without periodic array of metal nano-gaps. The self-spreading dynamics of the substrate without the architectures in electrolyte solution was quantitatively explained by the extended DLVO theory considering the van der Waals, electrostatic double layer, and hydration energies. Present findings suggest a possibility of controling the self-spreading dynamics by tuning the electrolyte concentration or substrate charge density. Furthermore, we demonstrated that the self-spreading dynamics was significantly affected due to the presence of nano-gaps. In addition to the change in the self-spreading dynamics, distribution of dye-labelled molecule doped in the self-spreading bilayer has also been changed. Both were strongly dependent on the gap width, i.e., narrower gap led to more pronounced effect on both the molecular distribution and the spreading dynamics. These phenomena have been attributable to the local compression induced during passing through the nano-gap.
The relation between the adsorption structure and the work function of succinic acid (HOOC-CH2-CH2-COOH) on Cu(110) surface, has been investigated as a function of the surface temperature using reflection absorption infrared spectroscopy, low energy electron diffraction, He atom scattering, temperature programmed desorption and Kelvin probe. From 350 to 450 K, succinic acid adsorbed as monosuccinate (HOOC-CH2-CH2-COO-) form. As the temperature increases, each monosuccinate make a dimer structure. From 450 K, monosuccinate changes to bisuccinate (-OOC-CH2-CH2-COO-) form. Bisuccinate structure is stable until 600 K and then desorption and dissociation occurred. The work function increased by adsorption due to ionization of molecules, and decreased with increasing the temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 K to 600 K the work function was constant, because of competition between desorption and change in the dipole moment of molecules, and then it reached the value of clean surface. It was experimentally clarified that the work function was affected by the difference in the state of conformation of molecules adsorbed.
Recently we have found that phase modulation atomic force microscopy (PM-AFM) has higher force sensitivity than amplitude modulation AFM (AM-AFM). The Q-control technique which is often utilized in AM-AFM allows to increase the effective Q-factor of the cantilever. In this study, we utilize the technique to PM-AFM and investigate the force sensitivity with and without the technique theoretically as well as experimentally. We show that the force sensitivity in PM-AFM is highly improved by the Q-control technique.
We introduce fluorescence in situ hybridization technique using scanning near-field optical microscopy (SNOM) as an example of scanning probe microscopy (SPM) in biology. This enables us to find out specific nucleotide sequences on a chromosome with high-spatial resolution exceeding the diffraction-limit.