Hydrolyzed hexagonal boron nitride/polymer nanocomposites for transparent gas barrier film.

A flexible thin gas barrier film formed by layer-by-layer (LBL) assembly has been studied. We propose for the first time that hexagonal boron nitride (h-BN) can be used in LBL assembly. When dispersed in water through sonication-assisted hydrolysis, h-BN develops hydroxyl groups that electrostatically couple with the cationic polymer polydiallyldimethylammonium chloride (PDDA). This process produces hydroxyl-functional h-BN/PDDA nanocomposites. The nanocomposites exhibit well exfoliated and highly ordered h-BN nanosheets, which results in an extremely high visual clarity, with an average transmittance of 99% in the visible spectrum. Moreover, well aligned nanocomposites extend gas diffusion path that reduce water vapor transmission rate to 1.3 × 10-2 g m-2 d-1. The simple and fast LBL process demonstrated here can be applied in many gas barrier applications.

Transparent resistive switching memory using aluminum oxide on a flexible substrate.

Resistive switching memory (ReRAM) has attracted much attention in recent times owing to its fast switching, simple structure, and non-volatility. Flexible and transparent electronic devices have also attracted considerable attention. We therefore fabricated an Al2O3-based ReRAM with transparent indium-zinc-oxide (IZO) electrodes on a flexible substrate. The device transmittance was found to be higher than 80% in the visible region (400-800 nm). Bended states (radius = 10 mm) of the device also did not affect the memory performance because of the flexibility of the two transparent IZO electrodes and the thin Al2O3 layer. The conduction mechanism of the resistive switching of our device was explained by ohmic conduction and a Poole-Frenkel emission model. The conduction mechanism was proved by oxygen vacancies in the Al2O3 layer, as analyzed by x-ray photoelectron spectroscopy analysis. These results encourage the application of ReRAM in flexible and transparent electronic devices.

Localized-surface-plasmon-enhanced multifunction silicon nanomembrane Schottky diodes based on Au nanoparticles.

Au nanoparticle (NP)-modified Si nanomembrane (Si NM) Schottky barrier diodes (SBDs) were fabricated by using a transfer-printing method to create pedestals using only one photomask on a flexible substrate. The transfer using the pedestals afforded a yield of >95% with no significant cracks. The plasmonic Au NPs can facilitate the improvement of the incident optical absorption. The Au NP-modified Si NM SBD exhibited enhanced photoresponse characteristics with an external quantum efficiency (η(EQE)) of 34%, a photosensitivity (P) of 27 at a voltage bias of -5 V, a light intensity of 1.2 W cm(-2), and a responsivity (R(ph)) of 0.21 A W(-1). Additionally, the mechanical bending characteristics of the device were observed while a compressive strain up to 0.62% was applied to the diode. The results suggest that the Au NP-modified Si NM SBD has great potential for use in multifunction devices as a strain sensor and photosensor.

Anisotropic magnetoresistance of an epitaxial Fe stripe grown on MgO/GaAs.

The anisotropic magnetoresistance of a [100] oriented Fe stripe grown on MgO/GaAs was investigated in order to elucidate the magnetization switching of patterned Fe. A 15 nm thick Fe film was epitaxially grown on MgO/GaAs layers using molecular beam epitaxy and a 50 microm x 4 microm shaped Fe stripe was patterned along its magnetic easy axis of [100]. Negative (positive) resistance peaks appear at room (low) temperature in magnetoresistance measurement. A reversal in sign of the peak was evidently observed with decreasing temperature. Such a reversal of resistance peak is caused by the competition between Lorentz force (ordinary) and spin-orbit (extraordinary) dominated scattering processes in a magnetic domain, which is significantly affected by temperature.

Gate bias-dependent junction characteristics of silicon nanowires suspended between polysilicon electrodes.

Realistic integration of 1D materials into future nanodevices is limited by the lack of a manipulation process that allows a large number of nanowires to be arranged into an integrated circuit. In this work, we have grown Si nanowire bridges using a thin-film catalyst in a batch process at 200 °C and characterized the produced devices consisting of a p+-Si contact electrode, a suspended Si nanochannel, and a polysilicon contact electrode. Both the electrodes and connecting lines are made of Si-based materials by conventional low-pressure chemical vapor deposition. The results indicate that these devices can act as gate-controllable Schottky diodes in integrated nanocircuits.

Synthesis of carbon-nitrogen nanostructures by hot isostatic pressure apparatus and their field emission properties.

Carbon-nitrogen (CN) nanofibers were synthesized in argon-nitrogen gas mixture at 75 MPa by high isostatic pressure (HIP) apparatus using a graphite resistive heater. The CN nanofibers were grown in random with the diameter of about 200 nm and the length over 5 microm. The structures obtained can be divided bamboo-like, spring-like, and bead necklace-like CN nanofibers. The nitrogen content of up to 8.4% was found in CN nanofibers by EELS analysis. Field emission results showed that the density of field emitters and the field enhancement factors changed by surface treatments and that CN nanofibers contained glass frit. The screen-printed CN nanofiber had a turn-on field of 2 V/microm.

Synthesis of double-walled carbon nanotubes by catalytic chemical vapor deposition and their field emission properties.

Double-walled carbon nanotubes (DWCNTs) were synthesized by catalytic chemical vapor deposition using Fe-Mo/MgO as a catalyst at 1000 degrees C under the mixture of methane and hydrogen gas. The nanotubes were purified by acid but were not damaged. Thermogravimetric analysis revealed the purity of the tubes to be about 90%. The high-resolution transmission electron microscopy image showed that DWCNTs have inner tube diameters of 1.4-2.6 nm and outer tube diameters of 2.3-3.4 nm. We observed radial breathing modes in Raman spectra, which are related to the diameter of inner nanotubes. The purified DWCNTs were mixed with organic vehicles and glass frit, and then they were screen-printed on glass substrate coated with indium tin oxide. The field emission properties of the screen-printed DWCNT films were examined by varying the amount of glass frit ingredient within the DWCNT paste. The results showed that DWCNT emitters had good emission properties such as turn-on field of 1.33-1.78 V/microm and high brightness. When the applied anode voltage was gradually increased, current density and brightness became saturated. We also observed DWCNTs adsorbed on the anode plate; they were DWCNTs peeled off from the cathode plate for field emission measurement.