The fabrication and characterization of fully visible-transparent and flexible ultraviolet (UV) detectors, on polyethylene 2,6-naphthalate (PEN) with active channels of zinc oxide nanowires and ohmic indium tin oxide contacts, are reported and discussed. The fabricated detector has an average transmittance of 80% in the visible spectral range and is most responsive at or below 370 nm, the onset of UV light, with a UV/vis rejection ratio of 1.42 × 103. A five orders of magnitude difference in the photocurrent, between UV illumination and dark conditions, are also observed. The single-sided UV response further shows that the PEN substrate performs well as a UV reflector. The noise analysis on the nanowire UV detector indicates a noise equivalent power and detectivity (D*) of 5.88 × 10−13 WHz−0.5 and 2.13 × 109 cm Hz0.5 W−1, respectively.

This work uniquely reports the synthesis of Zn x Mg 1– x O nanowires and submicron columns by utilizing a traditional carbothermal reduction process toward forming ZnO nanowire ultraviolet detectors, while simultaneously utilizing Mg 3 N 2 as the source of Mg. To investigate the relationship between Mg content in the ZnO lattice and the cutoff wavelength for high spectral responsivity, the nanowires were annealed in a series of designed conditions, whereas chemical, nanostructural, and optoelectronic characteristics were compared before and after treatment. Postanneal scanning electron micrographs revealed a reduction of the average ensemble nanowire dimensions, which was correlated to the modification of ZnO lattice parameters stemming from Zn 2+ dissociation and Mg 2+ substitution (confirmed via Raman spectroscopy). The analysis of cathodoluminescence spectra revealed a blueshift of the peak alloy band-edge emission along with a redshift of the ZnO band-edge emission; and both were found to be strong functions of the annealing temperature. The conversion of Zn 2 SiO 4 to Mg 2 SiO 4 (in O 2 ) and MgSiO 3 (in Ar) was found to correspond to transformations (shifting and scaling) of high-energy luminescence peaks and was confirmed with X-ray diffraction analysis. The tunability of the cutoff photodetection wavelength was evaluated as the nanowire arrays exhibited selective absorption by retaining elevated conduction under high-energy UV-C irradiation after thermal treatment but exhibiting suppressed conductivity and a single order of magnitude reduction in both spectral responsivity ( R λ ) and photoconductive gain ( G ) under UV-A illumination. Noise analysis revealed that the variation of detectivity ( D *) depended on the regime of ultraviolet irradiation, and that these variations are related to thermal noise resulting from oxygen-related defects on both nanowire and substrate surfaces. These results suggest a minor design tradeoff between the noise characteristics of thermally treated ZnMgO nanowire array UV detectors and the tunability of their spectral sensitivity.

This letter reports the methodology of a low-cost fabrication technique for producing periodic sub-micron structures over a large area, using a polymer mask. A thin film of gold/palladium or silica is deposited on a stretched polydimethylsiloxane (PDMS) substrate. Release of the tension forms a buckling sinusoidal pattern on the surface. The PDMS substrates are then used as masks in soft contact optical lithography, bypassing the need for an expensive lithographic process toward creating regular patterns on a traditional masks. Pattern transfers are conducted using an ultraviolet lamp and the fabrication of more complex periodic structures through multiple exposures is reported.

Two-terminal devices were fabricated using unintentionally doped Zinc Oxide (ZnO) nanowires (NW) grown via a chemical vapor deposition technique to study the influence of surface functionalization on their transport properties. Organic molecules with differing functional groups demonstrated contrasting effects on the charge transport of the nanowires depending on the polarity and orientation of the molecules.

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