There have been a lot of artificial superhydrophobic surfaces, however, those are difficult to use in daily purposes because of their brittle, stiff and breakable properties. We have been reported fabrication of superhydrophobic microstructured vulcanized rubber surfaces by using silicon microstructures as mold during their vulcanization process. Furthermore, the arrangement of microstructures could be repeatedly transformed from a hexagonal to linear patterns by elongations and superhydrophobicity was kept during elongation process. In this report, we prepared other type of superhydrophobic microstructured vulcanized rubber surfaces, which can be changed surface wettability by stretching. The superhydrophobic microstructured vulcanized rubber surfaces were prepared by using a silicon microstructures as mold. After observation of surface structures and wettability by laser microscopy and water contact angle analyzer, we took high-speed photography of water droplets felled to the rubber surfaces with different elongation rates, and theoretically discussed the differences of water behaviors.
We theoretically and computationally examined carrier localization in semiconducting edge-disordered graphene nanoribbons (ED-GNRs) with sub-100 nm lengths that correspond to the typical gate length for field-effect transistors. We numerically found that the localization length of ED-GNRs is proportional to the square of ribbon width and inversely proportional to the edge-disordered concentration. Furthermore, we obtained an analytical formula of the localization length in terms of the GNR width and the roughness concentration.
We propose a new quantum transport simulation method to investigate electronic transport with thermal atomic vibrations. Advantages of the simulation method are applicable to a super-micro-scale open system and to the direct evaluation of quantum decoherence from time-dependent current unlike conventional methods. In the present study, we investigate ballistic-diffusive crossover of metallic carbon nanotubes at room temperature and estimate mean free path characterizing the crossover and confirm that the results coincide with previous studies. Moreover, utilizing usefulness of our method, we succeed in evaluation of coherent-incoherent crossover and estimation of phase coherence length characterizing the crossover.
Molecular arrangements and electronic states of well-ordered Dinaphtho[2,3-b:2′3′-f]Thieno[3,2-b]-Thiophene (DNTT) and picene thin film on single crystal were measured by means of scanning tunneling microscope (STM) and angle-resolved photoemission spectroscopy, respectively. DNTT and picene form single crystalline-like molecular arrangement on inert Au(111) substrate. Splitting of HOMO energy due to overlapping with adjacent molecules was suggested by ultraviolet photoemission spectroscopy (UPS) and density functional theory (DFT) calculation. On the other hand, one-dimensional ordering of those molecule was observed on anisotropic Ag(110) substrate. However, the HOMO band dispersion was found to be 200 meV at maximum, showing that the overlapping of HOMO was smaller in such arrangement comparing with that in their single crystal.
According to the Wenzel model, the wetting properties can be tuned by controlling the two factors, the surface energy and the surface roughness. Evaluating the chemical and/or physical characteristics of PTFE surfaces before and after plasma treatment using XPS and FE-SEM, and radical species in plasma using OES cleared that an Ar/NH3-H2O plasma could provide that tuning, simultaneously generating a hydrophilic chemical structure and effective morphological roughness on PTFE surfaces and thus readily changing the highly hydrophobic surface to super hydrophilic.
Local hydration structures around boundary edges on heterostructures are essential for development of novel functional materials and devices. Recently we succeeded in visualizing atomic-scale local 3D hydration structures by using ultra-low noise frequency-modulation atomic force microscopy. However, a time-consuming 3D measurement on uneven heterogeneous surfaces has never been reported due to experimental difficulties. In this work, we investigate the local hydration structures around boundary edge between oppositely charged surfaces of a phyllosilicate by the previously established fast and nondestructive protocol and molecular dynamics simulation.
Control of an insulator and Ge, InGaAs, or GaN interface for metal-oxide-semiconductor field-effect transistors (MOSFETs) to overcome the limit of the Si material properties and the electrical properties have been discussed. An importance of a suitable interface control for each material properties was maintained for deriving the material properties in the MOSFETs. The author hope that the suitable interface control based on the well-understood interface structure and material properties leads to a robust fabrication process.
The failure process of Al2O3/epoxy adhesion by water intrusion is investigated by density-functional-theory (DFT) calculations. The water intrusion makes the interaction in the interface weaker. After that, by displacement of epoxy resin, the interaction is broken, so that the Al2O3/epoxy adhesion results in interface failure. The energy needed to this process is 0.9 eV, which is less than the energy generated by water adsorption on Al2O3 surface. Therefore, water can lead Al2O3/epoxy adhesion to interface failure easily.
To control the contamination resistance of polymer surface, hydrophilization and hydrophobization of polymer were attempted by two atmospheric pressure plasma (APP) treatments. Poly(ethylene terephthalate) film and fabric were treated by using APP-oxidation with nitrogen gas and APP-coating with hexametyldisiloxane (HMDSO). Wettability of polymer film and fabric was evaluated by the sessile drop and the Wilhelmy method. The APP-coating increased water and oil repellency, and the APP-oxidation remarkably reduced water contact angle. Characterization of polymer surface was conducted by X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and scanning electron microscope (SEM). The antifouling property of fabrics was investigated using carbon black and red clay as a model particulate soils.