Resistance in neuromorphic nanowire networks can be decreased when activated by voltage as multiple pathways of low resistance interconnected nanowires form, increasing nanowire to nanowire ...connectivity. We show that high connectivity regions are retained for a few minutes after the energy source is switched off. We have used this property to devise an associative device. With a multielectrode array, we send current through the network to connect together areas that are spatially associated with a given electrode combination forming a pattern. We correctly retrieve the stored patterns by passing a small current through the network at a later time even when we input a faulty or incomplete pattern as the network groups stored patterns into cluster of high associativity, in analogy with semantic memory association in the human brain.
Highly uniform and c-axis-aligned ZnO nanorod arrays were fabricated in predefined patterns by a low temperature homoepitaxial aqueous chemical method. The nucleation seed patterns were realized in ...polymer and in metal thin films, resulting in, all-ZnO and bottom-contacted structures, respectively. Both of them show excellent geometrical uniformity: the cross-sectional uniformity according to the scanning electron micrographs across the array is lower than 2%. The diameter of the hexagonal prism-shaped nanorods can be set in the range of 90–170 nm while their typical length achievable is 0.5–2.3 μm. The effect of the surface polarity was also examined, however, no significant difference was found between the arrays grown on Zn-terminated and on O-terminated face of the ZnO single crystal. The transmission electron microscopy observation revealed the single crystalline nature of the nanorods. The current–voltage characteristics taken on an individual nanorod contacted by a Au-coated atomic force microscope tip reflected Schottky-type behavior. The geometrical uniformity, the designable pattern, and the electrical properties make the presented nanorod arrays ideal candidates to be used in ZnO-based DC nanogenerator and in next-generation integrated piezoelectric nano-electromechanical systems (NEMS).
Adsorption of sulfuric acid species on various metal(111) electrodes in a 0.5 M H
2SO
4 solution was investigated by infrared reflection absorption spectroscopy (IRAS). Pt, Au, Ag, Cu and Rh(111) ...were used as electrodes. HSO
4
− is adsorbed on all of the surfaces including Pt, Rh, Au, Ag and Cu in a 0.5 M H
2SO
4 solution. Considerable amounts of sulfate in addition to bisulfate coexist on Ag(111) in a 0.5 M H
2SO
4 solution. Also, both DSO
4
− and SO
4
2− are coadsorbed on Au(111) in 0.5 M D
2SO
4+D
2O solution. The interconversion of HSO
4
−/H
3O
+ and H
2SO
4 that was seen on Pt(111) was not observed on the other electrodes. The frequencies of the SO
3 symmetric and S–OH stretching bands of a bisulfate adsorbed on the electrode surfaces are related to the electronic state of each M(111) surface.
A combined transmission electron microscopy (TEM) and Raman spectroscopy study has been performed on nanocrystalline Ba0.9Sr0.1TiO3 (BST) crystals and tubes. TEM investigations revealed the existence ...of 90 deg ferroelastic twins in the materials. Raman spectra showed an obvious shoulder (∼750 cm-1) from the broad band at ∼720 cm-1 that nominally represents the quasimode of E(LO4) and A1(LO3). The intensity of this shoulder increases with the twin population in the nanocrystalline materials, suggesting a correlation between the lattice dynamical characteristics and the long-range ferroelastic strain of the twin wall. The ferroelastic strain is mainly constrained along the c-axis of the BST unit cell, and the effect of this constraint is more pronounced in nanocrystalline materials than in bulks due to a significant wall volume ratio in twinned nano-materials. A1 phonons showing collective ion dynamics along the c-direction could be then hardened by the strain, while E symmetry exhibiting vibrations perpendicular to the c-axis would be less affected. The theoretically predicted giant LO–TO coupling in tetragonal ferroelectric perovskites 18 suggests that the hardening of the softest A1(TO1) mode in A1 symmetry is accompanied by that of the hardest A1(LO3) phonon. Consequently, the shoulder could be ascribed to the ferroelastic strain induced hardening of the quasimode with a considerable contribution from the A1(LO3) phonon.
We have developed a technique to prepare carbon nanotube (CNT) tip for scanning tunneling microscopy (STM). Using chemical vapor deposition, CNTs were directly grown from electrochemically etched ...tungsten tip. The STM images were routinely obtained for Si(1
1
1)7×7 surface with an atomic resolution using CNT tips as well as conventional metal tip.
The coadsorption of water and sulfur trioxide (SO
3) molecules on Pt(111) was studied by thermal desorption spectroscopy, in situ and ultra-high vacuum (UHV)-infrared reflection absorption ...spectroscopy with the intention of producing a double layer structure on a Pt(111) electrode surface in a 0.5 M H
2SO
4 acid solution. The vibrational frequencies of water, bisulfate and sulfuric acid molecules adsorbed on UHV model surfaces at temperatures ranging between 110 and 300 K were compared with those from an actual double layer in a 0.5 M H
2SO
4 acid solution under active potentials. Model structures on Pt(111) under UHV obtained from surfaces after 190 and 260 K annealing coincided well with those from electrode surfaces at a negative and a positive electrode potential, respectively. Sulfuric acid molecules on a Pt(111) electrode observed at 750–1100 mV were reproduced by dehydration from the coadsorbates of H
3O
+ and HSO
−
4 at 200–300 K.
Temperature dependence studies of adsorption of sulfuric acid species on Pt(1
1
1) and Au(1
1
1) electrodes were carried out using in situ infrared reflection absorption spectroscopy. A ...temperature-dependent shift of the interconversion potential between HSO
4
−/H
3O
+ and H
2SO
4 on a Pt(111) electrode was observed. A temperature-dependent frequency shift of the absorption bands of HSO
4
− was also observed on both Pt(1
1
1) and Au(1
1
1) electrodes in the potential region where a √3×√7 structure evolved. Modelling experiments in ultrahigh vacuum revealed that ordering of the overlayer water molecules played an important role in the frequency of the absorption bands of HSO
4
−.
The coadsorption of H
2O and SO
3 on Pt(111) has been studied as a model system for electrolyte-interface interaction under UHV conditions. The model double layer structures were characterized by low ...energy electron diffraction and infrared spectroscopy of water, bisulfate and sulfuric acid molecules adsorbed on a model surface at temperatures ranging between 110 and 400 K. They were compared with an actual double layer structure on a M(111) (M=Pt, Rh, Au, Cu and Ag) electrode surfaces in a 0.5 M H
2SO
4 acid solution under active potentials. Bisulfate ions (400–750 mV) and sulfuric acid molecules (750–1200 mV) adsorbed on a Pt(111) electrode under an active electrode surface were reproduced by a stepwise dehydration from the coadsorbates of H
3O
+ and HSO
4
− at 190 and 260 K, respectively. The model structure of the former bisulfate phase was (
3
×
7
), while that of the latter neutral sulfuric acid molecule phase was (
3
×
3
) R30°. The former bisulfate was found on all the surfaces, but the latter neutral sulfuric acid molecule was hardly observed on the Au, Cu and Ag surfaces.
Highly uniform and c-axis-aligned ZnO nanorod arrays were fabricated in predefined patterns by a low temperature homoepitaxial aqueous chemical method. The nucleation seed patterns were realized in ...polymer and in metal thin films, resulting in, all-ZnO and bottom-contacted structures, respectively. Both of them show excellent geometrical uniformity: the cross-sectional uniformity according to the scanning electron micrographs across the array is lower than 2%. The diameter of the hexagonal prism-shaped nanorods can be set in the range of 90-170 nm while their typical length achievable is 0.5-2.3 μm. The effect of the surface polarity was also examined, however, no significant difference was found between the arrays grown on Zn-terminated and on O-terminated face of the ZnO single crystal. The transmission electron microscopy observation revealed the single crystalline nature of the nanorods. The current-voltage characteristics taken on an individual nanorod contacted by a Au-coated atomic force microscope tip reflected Schottky-type behavior. The geometrical uniformity, the designable pattern, and the electrical properties make the presented nanorod arrays ideal candidates to be used in ZnO-based DC nanogenerator and in next-generation integrated piezoelectric nano-electromechanical systems (NEMS).
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