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A high-performance photodetector with the structure of NiO/SiO2/ZnO nanowires has been proposed. The devices with 6-nm-thick SiO2 exhibited a better rectification ratio ( J\mathrm {forward} / J\mathrm {reverse}) of 246 at ±2 V, lower dark current density ( J\mathrm {dark}) of 3.5\times 10^\mathrm -7 A/cm ^2 at a reverse bias of 2 V, and superior ultraviolet (UV) sensitivity ( I\mathrm {UV} / I\mathrm {dark}) of 16.23 than those without the SiO2 layer ( J\mathrm {forward} / J\mathrm {reverse} = 44, J\mathrm {dark} = 4.7\times 10^{\mathrm {-6}} A/cm ^2 , and I\mathrm {UV} / I\mathrm {dark} = 5.5) . The improved performance was mainly due to the ultrathin inserted SiO2 layer that builds a barrier height to minimize the transmission probability of low-energy carriers, leading to the enhancement of the UV sensing characteristics. [ABSTRACT FROM AUTHOR]

An extended-gate field-effect transistor (EGFET) with low-temperature hydrothermally synthesized \SnO2 nanorods as the pH sensor was demonstrated for the first time. The \SnO2 nanorod sensor exhibited the higher sensitivity of 55.18 \mV/\pH and larger linearity of 0.9952 in the wide sensing range of pH 1–13 with respect to the thin-film one. The nearly 15% sensitivity enhancement for such a sensor was attributed to the high surface-to-volume ratio of the nanorod structure, reflecting larger effective sensing areas. The characteristics of the output voltage versus sensing time also indicated good reliability and durability for the \SnO2 nanorod sensor. Furthermore, the hysteresis was only 3.69 mV after the solution was changed as \pH7 \rightarrow \pH3 \rightarrow \pH7 \rightarrow \pH11 \rightarrow \pH7. [ABSTRACT FROM AUTHOR]

Single-crystalline ZnO nanowires (NWs) were directly grown on Zn/glass substrates by using a low-temperature (i.e., 40 ^\circ\C) supercritical carbon dioxide (\SCCO2) fluid method. The optical, physical, and field-emission (FE) characteristics of the \SCCO2 -synthesized ZnO nanostructures are systematically investigated. ZnO NWs exhibited the low turn-on field of 3.16 \V/\mu\m at a current density of 10 \mu\A/cm^2 and a low threshold field of 4.38 \V/\mu\m at a current density of 1 \mA/cm^2. The current fluctuation of ZnO emitters was less than 8% at 5.3 \V/\mu\m in 12 h. The excellent FE properties of \SCCO2-synthesized ZnO emitters at low temperature make them a superior candidate for FE-based display devices. [ABSTRACT FROM PUBLISHER]

The pH sensing properties of an extended-gate field-effect transistor (EGFET) with Al-doped ZnO (AZO) nanostructures are investigated. The AZO nanostructures with different Al dosages were synthesized on AZO/glass substrate via a simple hydrothermal growth method at 85 ^\circ\C. The pH sensing characteristics of pH-EGFET sensors with an Al dosage of 1.98 at% can exhibit a higher voltage sensitivity of 57.95 mV/pH, a larger linearity of 0.9998, and a wide sensing range of pH 1–13, attributed to the well-aligned nanowire (NW) array, superior crystallinity, less structural defects, and better conductivity. Consequently, the hydrothermally grown AZO NWs demonstrate superior pH sensing characteristics and reveal the potentials for flexible and disposable biosensors. [ABSTRACT FROM PUBLISHER]

A novel coaxial-structured amorphous-silicon (a-Si) p-i-n solar cell with 1-\mu\m-long low-temperature hydrothermally synthesized Al-doped-ZnO (AZO) nanowires was demonstrated for the first time. The conversion efficiency \eta increased from 3.92% to 4.27% when the intrinsic a-Si thickness was increased from 25 to 150 nm and then decreased to 3.66% when the intrinsic layer thickness was further increased to 250 nm. It was attributed to an excessively thick intrinsic a-Si layer that would decrease the internal electrical field and interfere with charge separation. With the optimum intrinsic a-Si thickness of 150 nm, the conversion efficiency increased from 4.27% to 4.73% when the AZO wire length was increased from 1 to 2 \mu\m. Moreover, the proposed coaxial-structured solar cell exhibited a nearly 46% efficiency enhancement over a conventional a-Si thin-film solar cell. [ABSTRACT FROM AUTHOR]

High-performance zinc oxide (ZnO) bottom-gate (BG) thin-film transistors (TFTs) with a single vertical grain boundary in the channel have been successfully fabricated by a novel low-temperature (i.e., 85 ^\circ\C) hydrothermal method. The ZnO active channel was laterally grown with an aluminum-doped ZnO seed layer underneath the Ti/Pt film. Consequently, such BG-TFTs (W/L = \250\ \mu\m/\10\ \mu\m) demonstrated the high field-effect mobility of 9.07 \cm^2/\V\cdot \s, low threshold voltage of 2.25 V, high on/off-current ratio above \10^6, superior current drivability, indistinct hysteresis phenomenon, and small standard deviations among devices, attributed to the high-quality ZnO channel with the single grain boundary. [ABSTRACT FROM AUTHOR]

Abstract: An extended-gate field-effect transistor (EGFET) of coaxial-structured ZnO/silicon nanowires as pH sensor was demonstrated in this paper. The oriented 1-μm-long silicon nanowires with the diameter of about 50nm were vertically synthesized by the electroless metal deposition method at room temperature and were sequentially capped with the ZnO films using atomic layer deposition at 50°C. The transfer characteristics (IDS–V REF ) of such ZnO/silicon nanowire EGFET sensor exhibited the sensitivity and linearity of 46.25mV/pH and 0.9902, respectively for the different pH solutions (pH 1–pH 13). In contrast to the ZnO thin-film ones, the ZnO/silicon nanowire EGFET sensor achieved much better sensitivity and superior linearity. It was attributed to a high surface-to-volume ratio of the nanowire structures, reflecting a larger effective sensing area. The output voltage and time characteristics were also measured to indicate good reliability and durability for the ZnO/silicon nanowires sensor. Furthermore, the hysteresis was 9.74mV after the solution was changed as pH 7→pH 3→pH 7→pH 11→pH 7. [Copyright &y& Elsevier]

Abstract: In this paper, a simple self-assembled lateral growth of ZnO nanowires (NWs) photodetector has been synthesized by a hydrothermal method at a temperature as low as 85°C. The ZnO NWs exhibit single-crystalline wurtzite with elongated c-axis and can be selectively lateral self-assembled around the edges of ZnO seeding layer. The current of ZnO NWs is sensitive to the variation of ambient pressures, i.e. 4.47μA was decreased to 1.48μA with 5V-bias as 1.1×10−6 Torr changed to 760Torr, accordingly. Moreover, the current–voltage characteristics of ZnO NWs photodetectors can be evidently distinguished by UV illumination (i.e. λ =325nm). The photocurrent of ZnO NWs with UV illumination is twice larger than dark current while the voltage biased at 5V. Consequently, this faster photoresponse convinces that the hydrothermally grown lateral ZnO NWs devices have a fairly good for the fabrication of UV photodetectors. [Copyright &y& Elsevier]