Xijian Zhang

Superhydrophobic metallic glass surface with superior mechanical stability and corrosion resistance

Superhydrophobic surface with mechanical stability and corrosion resistance is long expected due to its practical applications. We show that a micro-nano scale hierarchical structured Pd-based metallic glass surface with superhydrophobic effect can be prepared by the thermoplastic forming, which is a unique and facile synthesis strategy for metallic glasses. The superhydrophobic metallic glass surface without modification of low surface energy chemical layer also exhibits superior mechanical stability and corrosion resistance compared with conventional superhydrophobic materials. Our results indicate that the metallic glass is a promising candidate superhydrophobic material for applications.

Structural properties and photoluminescence of zinc nitride nanowires

Zinc nitride nanowires can be synthesized by nitridation reaction of zinc powder with ammonia gas in 500ml∕min at the nitridation temperature of 600 °C for 120 min. Studies by using x-ray diffraction indicate that zinc nitride nanowires are cubic in structure with the lattice constant a=0.9788nm. Observations by using scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy show that zinc nitride is of nanowire structure. Typical room temperature photoluminescence spectrum of zinc nitride nanowires exhibits an ultraviolet emission peak at 385 nm (3.22 eV) and a blue emission band centered at 450 nm (2.76 eV).

Graphene ballistic nano-rectifier with very high responsivity

Although graphene has the longest mean free path of carriers of any known electronic material, very few novel devices have been reported to harness this extraordinary property. Here we demonstrate a ballistic nano-rectifier fabricated by creating an asymmetric cross-junction in single-layer graphene sandwiched between boron nitride flakes. A mobility ∼200,000 cm2 V−1 s−1 is achieved at room temperature, well beyond that required for ballistic transport. This enables a voltage responsivity as high as 23,000 mV mW−1 with a low-frequency input signal. Taking advantage of the output channels being orthogonal to the input terminals, the noise is found to be not strongly influenced by the input. Hence, the corresponding noise-equivalent power is as low as 0.64 pW Hz−1/2. Such performance is even comparable to superconducting bolometers, which however need to operate at cryogenic temperatures. Furthermore, output oscillations are observed at low temperatures, the period of which agrees with the lateral size quantization.

Performance regeneration of InGaZnO transistors with ultra-thin channels

Thin-film transistors (TFTs) based on ultra-thin amorphous indium gallium zinc oxide (a-IGZO) semiconductors down to 4 nm were studied motivated by the increasing cost of indium. At and below 5 nm, it was found that the field-effect mobility was severely degraded, the threshold voltage increased, and the output characteristics became abnormal showing no saturated current. By encapsulating a layer of polymethyl methacrylate on the IGZO TFTs, the performance of the 5-nm-thick device was effectively recovered. The devices also showed much higher on/off ratios, improved hysteresis, and normal output characteristic curves as compared with devices not encapsulated. The stability of the encapsulated devices was also studied over a four month period.

Thermally Evaporated SiO Serving as Gate Dielectric in Graphene Field-Effect Transistors

A thermally evaporated silicon monoxide (SiO) film has been experimented as the gate dielectric in graphene field-effect transistors (GFETs) due to its room-temperature and low-damage deposition without introducing chemical gases or ionized particles as in other film deposition techniques, which may cause damage to graphene. In order to evaluate the dielectric properties, a double-gated GFET was fabricated with a standard commercial thermally grown SiO2 layer as the bottom gate dielectric and thermally evaporated SiO as the top dielectric. The electrical characterizations revealed that the top-gate carrier mobility was 1081.3 cm2/Vs, reasonably comparable to the bottom-gate mobility. Furthermore, the breakdown strength of the SiO film reached 5.7 MV/cm, which was lower than that of the SiO2 dielectric (~10 MV/cm) but in the same order of magnitude. The breakdown mechanism of the SiO film was studied, and the current-voltage characteristics were in agreement with the Frenkel–Poole emission model. Finally, the relative dielectric constant of SiO was found to be 5.3, significantly higher than that of SiO2 (3.9). These results indicate that the thermally evaporated SiO can function as an excellent dielectric for graphene-based devices.

Characteristics of sputtered Y-doped IZO thin films and devices*

Yttrium-doped IZO (YIZO) thin films with different thickness have been prepared on soda-lime glass (SLG) and P-Si substrates by radio frequency magnetron sputtering at room temperature. Structural morphology and optical properties of the films have been investigated. YIZO thin film transistors (TFTs) with the bottom-gate-structure are fabricated on P-Si substrates. The output and transfer characteristics of YIZO-TFT have been studied. It has been found that all YIZO thin films prepared at room temperature are amorphous, and the YIZO TFTs exhibit n-channel depletion mode. YIZO-TFT with active layer thickness of 20 nm shows an on/off ratio over 10 5 , a sub-threshold swing of 2.20 V/decade at a low operating voltage of -1.0 V, and saturation mobility values over 0.57 cm 2 /(V· s).