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We investigated the photoconductivity of single ZnO nanowire device as a function of the surrounding atmosphere, considering the comparison between reduced pressure, inert gas environments, and air. We show that after UV excitation the photocurrent persists for hours, in particular in vacuum, nitrogen, and argon. In the presence of oxygen, the photodecay rate is initially fast but then becomes considerably slower, resulting in a long persisting photo-conductivity tail. Our proposed model explains the persistence of the photoconductivity (PPC) in terms of band bending at the surface of the nanowires, which is related to the trapping of electrons from the conduction band.

Tunable nanoscale light emitters are essential to accomplish future multifunctional optoelectronic nano-devices. Here, we present an approach for achieving red electroluminescence from single ZnO nanowires (NWs) implanted with europium ions. The electroluminescence is emitted mainly from the end facets of ZnO NWs at room temperature under the application of an AC voltage. The corresponding electroluminescence spectrum is attributed to the radiative intrashell transitions of the Eu ions, while contributions from near band edge or deep level emission of the ZnO remain absent. The total intensity of the electroluminescence is linearly proportional to the length of the NWs, whereas there is no clear correlation with other morphology factors of the NW based device such as the diameter. Furthermore, the underlying excitation mechanism of the electroluminescence is proposed as direct-impact excitation of Eu ions by hot electrons in the ZnO NWs. [ABSTRACT FROM AUTHOR]

We investigated the modulation of the photoconductivity under below-band gap excitation in single ZnO nanowire field effect transistors. Light excitation at 550 nm does not induce any change in the drain–source current when the gate voltage is kept at Vgs = 0 V, but results in a current increase when it is set to Vgs = −50 V. At this negative value of the gate voltage we further investigated the photo-reaction in the below-band-gap range 400–800 nm, observing a qualitative similar profile for all the photo-current curves. These results were attributed to a local effect, suggesting that the change in conductivity is due to the release of electrons from interface states located between the ZnO nanowire active channel and the gate dielectric SiO2. [ABSTRACT FROM AUTHOR]