We have fabricated high-performance enhancement and depletion mode (E-and D-mode) top-gate metal-insulator-semiconductor field-effect transistors (T-G MISFETs) using two kinds of CdS nanobelts (NBs), labeled as NB A and NB B, respectively. High-k HfO 2 dielectric is used as the insulator layer. The thicknesses of NBs A and B are about 60 and 180 nm, respectively. The threshold voltage and subthreshold swing of the CdS NB A T-G MISFET are about 0.15 V and 62 mV/dec, respectively. The on/off ratio is about 6 Â 10 4 , which is the best result for E-mode CdS nanoFETs reported so far. The threshold voltage, on/off ratio and peak transconductance of the CdS NW B T-G MISFET are about À3.4 V, 2 Â 10 9 , and 11 mS, respectively. The on/off ratio, to the best of our knowledge, is the highest reported for nanoFETs so far. Both of the two kinds of T-G MISFETs have quite small hysteresis in their transfer characteristics. The mechanisms for the different gate transfer characteristics are discussed. Corresponding Si back-gate CdS NB MISFETs each with a 600 nm SiO 2 film as the insulator layer are also measured for comparison.
Single-crystalline Zn 3 P 2 nanowires (NWs) have been synthesized on silicon (Si) substrates via a vapor phase transport method. Zn (99.99%) powder and InP (99.99%) fragments were used as the sources, and 10 nm thick thermal evaporated gold (Au) film was used as the catalyst. The as-prepared Zn 3 P 2 NWs have diameters of 100-200 nm and lengths of more than 10 mm. Single NW metalinsulator-semiconductor field-effect transistors (MISFETs) based on Zn 3 P 2 NWs were fabricated. Electrical transport measurements show that the as-grown Zn 3 P 2 NWs are of p-type. The hole concentrations and mobilities of the p-type Zn 3 P 2 NWs are about 5.6 Â 10 16 cm À3 and 42.5 cm 2 V À1 s À1 , respectively. The on-off ratio of the MISFET is about 4 Â 10 4 , and its threshold voltage and transconductance are 2.5 V and 35 nS, respectively. These parameters indicate that the p-type Zn 3 P 2 NWs are of high quality, and may have potential applications in nanoscale electronic and optoelectronic devices.
Carassius auratus were exposed to mixtures of constant free lead (0. 1 mg/L) and particulate lead (adsorbed on gibbsite particles) at varied concentrations (0, 0.4, 0.8, 1.2, 2.0, and 3.0 mg/L). The concentrations of lead and aluminum in the gills and intestines of the fish were determined after exposure. The gills were examined (after the exposure) with a light microscope for any particles adhering to the surface. The examination results revealed that lead accumulations on the gills increased with increased particulate lead concentrations in the ambient water (under conditions of a constant level of free lead), indicating the bioavailability of lead via the gills. Gibbsite particles were also observed on the gill surface after exposure. The ratio of lead and aluminum in the gills was much higher than that in the particles. Our results suggest that there was a two-step process involved in the uptake of particulate lead by fish gills: (1) adherence of the particles on the gill surface where mucus was attached; and (2) desorption of lead from the particles under conditions of the gill microenvironment.
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