Wear and dynamic properties of piezoelectric ultrasonic motor with frictional materials coated stator

Piezoelectric ultrasonic motors have been studied, developed and utilized by researchers and companies all over the world. Ultrasonic motors (USM) produce rotational motion based on traveling waves made by the resonant vibrations of piezoceramic. These motors have been recently developed and utilized in practical applications. The dynamic properties and life of piezoelectric ultrasonic motors are strongly related to the frictional material Fused on the sliding surface. In this study, effects of frictional material properties on the performances of piezoelectric ultrasonic motors are investigated. It was possible to improve the torque of a traveling wave type ultrasonic motor by stator's coating.     

Optimization of a piezoelectric linear motor in terms of the contact parameters

The contact kinetics of piezoelectric linear motors determines the operational characteristics like speed and torque or transmitted mechanical power and efficiency. Piezoelectric linear motors are driven by tangential stress in the interface between tip of shaking beam and slider. A good contact between the tip and slider is necessary for a reliable analysis of the motor, which is needed for the optimization of its performance. The piezoelectric linear motor was fabricated and the characteristics of the motor were investigated by external conditions such as tip shape with different curvatures and contact force between the tip and the slider. It was found in this investigation that the optimal curvature of the tip and the contact force are curvature of 1 and 10, respectively, for the high actuating speed, and curvature of 1 and 40 N, respectively, for the high actuating force. Finally, tip shape has an influence on the characteristics of linear motor.     

Electrical Characteristics of Hybrid Nanoparticle–Nanowire Devices

Gold nanoparticles synthesized by a colloidal method were deposited in an Al₂O₃ dielectric layer of an omega-gated single ZnO nanowire FET. These gold nanoparticles were utilized as localized trap sites. The adsorption of the gold nanoparticles on an Al₂O₃-coated ZnO nanowire was confirmed by high-resolution transmission electron microscopy. In this study, a hybrid nanoparticle-nanowire device was fabricated by conventional Si processing. Its electrical characteristics indicated that electrons in the conduction band of the ZnO nanowire can be transported to the localized trap sites by gold nanoparticles for gate voltages greater than 1 V, through the 10-nm-thick Al ₂O₃ tunneling oxide layer.     

Switching memory cells constructed on plastic substrates with silver selenide nanoparticles

Programmable metallization cell (PMC) memory is a kind of next generation non-volatile memory that has attracted increasing attention in recent years as a possible replacement for flash memory. In spite of the considerable amount of research focused on the fabrication of non-volatile memories on plastic substrates with lightweight, thin, and bendable characteristics, there have been few studies on the fabrication of PCM memory on flexible substrates. In this study, we synthesized Ag₂Se nanoparticles (NPs) by a positive-microemulsion method and constructed PMC memories on plastic substrates with programmable layers formed by the spin-coating of the Ag₂Se NPs. To the best of the knowledge, this is the first attempt to construct PMC memory on plastic substrates by the spin-coating of Ag₂Se NPs. The Ag₂Se NPs synthesized in this study had a uniform size of 2 nm and interestingly showed α-phase (high temperature phase) stability at room temperature. Switching behaviors were observed through the voltage scanning on the fabricated memories with applicable switching voltages. However, the resistance ratios of the off-state to the on-state were quite small. The possible reasons for the α-phase stability of the Ag₂Se NPs at room temperature and the detailed memory characteristics will be described in this article.     

Electrically driven lasing in light-emitting devices composed of n-ZnO and p-Si nanowires

Electrically driven lasing was demonstrated in light-emitting devices composed of n-ZnO and p-Si nanowires (NWs). The ZnO NWs were synthesized by thermal chemical vapor deposition and the Si NWs were formed by crystallographic wet etching of a Si wafer. The p-n heterojunction devices were constructed using the NWs by the direct transfer and dielectrophoresis methods. At an excitation current of 2 μA, the electroluminescence spectrum showed lasing behavior, and this phenomenon was explained by the ZnO-nanostructure-related cavity property.     

Flexible photodiodes constructed with CdTe nanoparticle thin films and single ZnO nanowires on plastics

We construct a flexible pn heterostructured photodiode using a CdTe nanoparticle thin film and a single ZnO nanowire (NW) on a plastic substrate. The photocurrent characteristics of the flexible photodiode are examined under illumination with 325 nm wavelength light and the photocurrent efficiencies at bias voltages of ± 2.5 V are estimated to be 8.0 and 2.1 μA W(-1) under forward and reverse bias conditions, respectively. The photocurrent generation of the pn heterostructured photodiode is dominantly associated with the transport of the photogenerated charge carriers in the single ZnO NW. Furthermore, the operations of our flexible photodiode are investigated in the upwardly and downwardly bent states, as well as in the flat state.     

N-channel thin-film transistors constructed on plastic by solution processes of HgSe nanocrystals

We demonstrate bottom-gate thin-film transistors (TFTs) based on solution-processed HgSe nanocrystals (NCs) on plastic substrates. Solid films made of spin-coated HgSe NCs were heated at a temperature of 150 °C for 15 min to maximize the magnitude of their current, and these films were utilized as the channel layers of TFTs. A representative TFT with a bottom-gate Al₂O₃ layer operated as a depletion-mode one with an n-channel, exhibiting a field effect mobility of 3.9 cm²/Vs and an on/off current ratio of about 10². In addition, the electrical characteristics of the TFT on bent substrates are briefly described.     

Redshifting and broadening of quantum-well infrared photodetector'sresponse via impurity-free vacancy disordering

The partial intermixing of the well and barrier materials offers unique opportunities to shift locally the bandgap of quantum-well (QW) structures. We have demonstrated redshifting and broadening of the wavelength responses of bound-to-continuum GaAs and InP based quantum-well infrared photodetectors (QWIP's) after growth via impurity-free vacancy disordering (IFVD). A comprehensive set of experiments is conducted on QWIP's fabricated from both as-grown and multiple-quantum-well (MQW) structures. Compared to the as-grown detector, the peak spectral responses of the disordered detectors were shifted to longer wavelengths. The peak absolute response of the disordered GaAs based QWIP is lower by almost a factor of four. However, the responsivity characteristics of the disordered InP based QWIP show no major degradation. In general, with the spectral broadening taken into account, the overall performance of the disordered QWIP's has not dropped significantly. Thus, the postgrowth control of the QW composition profiles by impurity-free vacancy disordering offers unique opportunities to fine tune various aspects of a photodetector's response. Theoretical calculations of the absorption coefficient spectrum are in excellent agreement with the experimental data     

ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al(2)O(3) gate oxides

The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al(2)O(3) tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8?V was observed in its drain current versus gate voltage (I(DS)-V(GS)) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper.     

Si-based flexible memristive systems constructed using top-down methods

Si-based memristive systems consisting of Ag, amorphous Si, and heavily doped p-type Si nanowires were successfully constructed on plastic substrates through top-down methods, including the crystallographic wet etching of Si wafers, transfer onto plastic substrates, and thin film patterning. The memristive systems showed excellent memory characteristics and flexibility, such as intrinsic hysteric and rectifying behaviors, on/off resistance ratios of >1 × 10(5), and durability for up to 1000 bending cycles. The correlations between the Ag-filament-related nanostructures formed in amorphous Si and the resistance-switching behaviors were carefully examined with the tunneling current model, transmission electron microscopy, and secondary ion mass spectroscopy to explore the switching mechanism. Our study suggests the promising potential of the Si-based memristive systems for the development of next-generation flexible nonvolatile memory.