Argon ion sputtering is one of the most accepted techniques for depth profiling in practical X-ray photoelectron spectroscopy (XPS) analysis, while this technique is known to cause severe degradation especially with organic materials. Sputtering system using buckminsterfullerene (C60) ion beam has recently been introduced to XPS apparatus as a new sputtering tool for depth profiling. It enables the XPS depth analysis of organic materials such as photoresists without chemical damages. In this paper, the XPS analysis using the C60 ion sputtering was applied to examine the depth distributions of a fluoropolymer in ArF immersion resists to clarify the mechanism of the water-repellency change between the co-polymer and blend polymer. In addition, the depth profiling of the resist is compared to those observed with other techniques such as angle resolved XPS analysis and XPS analysis on the gradient shaved surfaces.
Isolated water molecules such as monomers and dimers on Pt(111) surfaces with low degree of coverage were directly observed by scanning tunneling microscopy (STM) at low temperatures. A water monomer is shown as a single protrusion in the STM image. While, a dimer appears as a 6-fold symmetric “flower-like” protrusion, which can be explained by the model that one of the water molecules in the dimer is rotating around the other. The adsorption sites of a dimer were also determined as both molecules on atop sites. Indeed, we have succeeded in forming and breaking dimers by exciting molecular vibrations with inelastically tunneled electrons from an STM tip. It turns out that a dimer is more stable than a monomer when the sample bias voltage is shifted. We also report on vibrationally induced lateral hopping motion of both monomer and dimer molecules by injecting tunneling electron.
We have mechanically fabricated Ni and Pd nanoconstrictions and investigated their conductance characteristics in solution under electrochemical potential control. When the electrochemical potential of the Ni and Pd nanoconstrictions was kept at the hydrogen evolution potential, clear features appeared at 1−1.5 G0 (G0 = 2e2/h) and at 1 G0 in the conductance histogram of Ni and Pd, respectively. Based on the experimental results previously obtained in ultra high vacuum at ultra low temperature and theoretical calculation, the peaks observed in the present system (1−1.5 G0 for Ni, 1 G0 for Pd) were assigned to the mono atomic contact. While the fabrication of mono atomic contacts of Ni and Pd is difficult at room temperature, the mono atomic contacts could be stabilized in solution by hydrogen adsorption. The stability of the Pd atomic contact was qualitatively analyzed using conductance traces. The atomic contact could be stretched 0.4 nm in length just before breaking, suggesting the formation of the Pd wire.
Surface geometric structures of rutile TiO2(011) are determined by a combination of non-contact atomic force microscopy (NC-AFM), scanning tunneling microscopy (STM) and density functional calculations. Microfaceting missing-row structural models proposed instead of a previous titanyl (Ti=O) double-bond model can explain the experimental results very well. Calculated images for NC-AFM and STM are in good agreement with the experimental data. Decreasing the density of dangling bonds stabilizes the surface energy, which results in the microfaceting missingrow (n×1) reconstructions.
We report a simple method for fabricating metal nanoarrays with DNA templates. After DNA-stretching and fixation on surfaces, highly aligned and integrated Au nanoarrays were fabricated via electroless depositions of Au on DNA. The direct visualization of metallic nanoarrays and interaction with optical near-filed have been studied by atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). The resulting metallic nanoarrays are attractive prospects in nano-optics and an important step toward the construction of plasmon waveguids.
We have succeeded in observing vibrationally induced inelastic structures in the photoemission spectra of carbon monoxide or oxygen covered Cu(001) surfaces excited by laser light. The structure appears as a step at the vibrational energy below the Fermi level. We found that the CO/Cu(001) spectra contain two step structures arising from the C-O internal stretching mode and the frustrated rotation mode. These steps shift to lower energy for 13C18O. In the O/Cu(001) spectra we have observed the inelastic structures originating from not only adsorbate-substrate vibrations but also substrate surface phonons.
We have fabricated a planar type ion channel biosensor useful for the high throughput screening by using SOI (Silicon On Insulator) substrates. The micro-pore of about 1μm diameter was formed through the SOI substrate and controlled the structure of the pore. The substrate was assembled into the micro fluid circuit. Comparing with classical patch-clamp using the pipette, the planar type patch-clamp has advantages not only in the miniaturization and the high integration, but also in easiness of intracellular fluids exchange and of simultaneous measurement of ion channel current and fluoresce imaging. The HEK293 (Human Embryonic Kidney 293) cell with transfected TRPV1 (transient receptor potential vanilloid type 1) channels, which are mainly expressed in sensory nerve cells, was positioned on the micro-pore, and the capsaicin, which is a pungent ingredient of the hot pepper, was added to the external cell solution as a ligand molecule, then the whole-cell current of the ion channel was measured.
The interaction between ferritin and solid substrates was directly measured with an atomic force microscope (AFM). Our interest was focused on the effect of the modification of the N-terminal domains of the ferritin molecules on the long- and short-range interactions. Based on the results of AFM, we report the factors to determine the ferritin-substrate interactions as well as the mechanism underlying the specificity of Ti-binding peptide.
The importance of work function measurement in the field of application has greatly increased. The principle of work function measurement using electron spectroscopic methods such as UPS, XPS and AES is explained. The practical tips for measurements and analysis are advised with reasons.