Studies of carrier transport mechanism in NiO/Ag/NiO transparent conducting electrode/ZnO metal-semiconductor-metal photodetectors.

Oxide/metal/oxide multilayers as a transparent conducting electrode (TCE) have been developed to replace metals due to their high transparency and low sheet resistance. Nickel oxide (NiO) film with a high work function was used as an oxide to form NiO/Ag/NiO (NAN) TCE, therefore a high barrier height between NAN/zinc oxide (ZnO) interface. In the study, NAN TCE was deposited on ZnO surface to fabricate metal-semiconductor-metal (MSM) photodetectors (PDs) and study its carrier transport mechanism. The NAN TCE has a low sheet resistance of 6.5 Ω/sq. and transmittance more than 40% in a 300-1000 nm wavelength range. Such issues result in the figure-of-merit is higher (2.3 × 10-4Ω-1) than that (2.5 × 10-7Ω-1) of pure single NiO thin film. As compared to the conventional Au/ZnO MSM-PDs, the NAN/ZnO MSM-PDs demonstrates a lower leakage current as a result of Ni atoms diffusing into ZnO and passivating the defects. Due to the high work function of NiO, the NAN/ZnO interface exhibits a barrier height as high as 0.91 eV. The Au/ZnO MSM-PDs reveals only one carrier conduction of ohmic due to the electrons tunnel form Au into ZnO through the surface defects. In contrast, two distinct carrier transport mechanisms were observed in the NAN/ZnO MSM-PDs. At low-voltage forV⩽0.64 V, ohmic conduction dominates and the electrons inject from NAN to ZnO, trapped by the defect states of ZnO. At high-voltage for V⩾0.64 V, the trapped electrons acquire enough energy and emit from trap to conduction band, entering Poole-Frankel emission transport.

Nanoscale Removal of Picosecond Laser Ablation for Polymer.

This paper analytically investigates the picosecond laser ablation of polymer. Laser-pulsed ablation is a well-established tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface as the ablation mechanisms and is applied to predict the laser-ablated depth of Acrylonitrile Butadiene Styrene/PolyVinyl Chloride (ABS/PVC). The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. The effects of material properties and processing parameters on the ablation depth per pulse are discussed for picosecond laser processing of ABS/PVC.

Effect of nonenzymatic glycation of albumin and superoxide dismutase by glucuronic acid and suprofen acyl glucuronide on their functions in vitro.

Acyl glucuronides bind irreversibly to plasma proteins, and one mechanism proposed for this covalent binding is similar to that for glycation of protein by reducing sugars. Because glycation of protein by glucose and other reducing sugars can alter protein function, this lead to the hypothesis that the glycation of proteins by acyl glucuronides may cause similar effects. When human serum albumin (HSA) was incubated with 0.5 M glucose for 5 days, the unbound fractions of diazepam and warfarin were increased by 41 and 35%, respectively, less than that caused by glucuronic acid which increased the unbound fractions by 90% for diazepam and 420% for warfarin. When HSA was incubated with suprofen glucuronide (SG) at a much lower concentration of 0.005 M for only 24 h, the effects on the unbound fractions of diazepam and warfarin to HSA were altered dramatically with increases of 340 and 230%, respectively. After incubation of superoxide dismutase (SOD) with 0.5 or 1 M reducing sugars for 14 days, the enzyme activity decreased to 82 and 61% of initial levels at day 14, respectively, whereas glucuronic acid almost completely inactivated the enzyme activity over the same period. Even at a very low concentration (0.005 M) of SG, SOD activity was reduced significantly to 11% of initial levels by day 14, which was comparable to the effect by 0.5 and 1.0 M concentrations of glucuronic acid. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and matrix associated laser desorption/ionization time of flight mass spectrometry indicated that several equivalents of reducing sugars or SG became attached to albumin after incubation. These results suggest that acyl glucuronides may affect the function of proteins by the formation of glycated protein in vivo and may be associated with the toxicity of xenobiotics metabolized to labile acyl glucuronides.