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Single nanowire-based UV photodetectors for fast switching.

Ul Hasan K, Alvi NH, Lu J, Nur O, Willander M - Nanoscale Res Lett (2011)

Bottom Line: Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs.The photodetector shows high stability, reversibility, and sensitivity to UV light.The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science and Technology (ITN) Linköping University, Campus Norrköping, SE-601 74 Norrköping, Sweden. kamran.ul.hasan@liu.se.

ABSTRACT
Relatively long (30 µm) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

No MeSH data available.


Related in: MedlinePlus

Photoresponse of a single ZnO nanowire under pulsed illumination by a 365 nm wavelength UV light with (a) Schottky contact on one side, and (b) ohmic contacts on both sides.
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Figure 4: Photoresponse of a single ZnO nanowire under pulsed illumination by a 365 nm wavelength UV light with (a) Schottky contact on one side, and (b) ohmic contacts on both sides.

Mentions: Photoconductive response is a key figure of merit for a photodetector. Response of both the ohmic and Schottky devices was measured using a 365-nm UV source at a bias of 0.5 V (Figure 4). The real time ON/OFF switching was measured by applying a UV pulse with an intensity of 1.5 mW/cm2. The measured photocurrent shows a rapidly rise and fall upon exposure to UV light for the Schottky detector and the current decreases down to 35 nA, which is quite close to the initial value under dark. Photocurrent pulse shows good stability and reversibility. Whereas, the recovery time is much higher for the ohmic detector and the value of the dark current is also relatively higher. Thus, the Schottky diode shows much faster switching under pulsed UV illumination as compared to the device with ohmic contacts on both the sides.


Single nanowire-based UV photodetectors for fast switching.

Ul Hasan K, Alvi NH, Lu J, Nur O, Willander M - Nanoscale Res Lett (2011)

Photoresponse of a single ZnO nanowire under pulsed illumination by a 365 nm wavelength UV light with (a) Schottky contact on one side, and (b) ohmic contacts on both sides.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211437&req=5

Figure 4: Photoresponse of a single ZnO nanowire under pulsed illumination by a 365 nm wavelength UV light with (a) Schottky contact on one side, and (b) ohmic contacts on both sides.
Mentions: Photoconductive response is a key figure of merit for a photodetector. Response of both the ohmic and Schottky devices was measured using a 365-nm UV source at a bias of 0.5 V (Figure 4). The real time ON/OFF switching was measured by applying a UV pulse with an intensity of 1.5 mW/cm2. The measured photocurrent shows a rapidly rise and fall upon exposure to UV light for the Schottky detector and the current decreases down to 35 nA, which is quite close to the initial value under dark. Photocurrent pulse shows good stability and reversibility. Whereas, the recovery time is much higher for the ohmic detector and the value of the dark current is also relatively higher. Thus, the Schottky diode shows much faster switching under pulsed UV illumination as compared to the device with ohmic contacts on both the sides.

Bottom Line: Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs.The photodetector shows high stability, reversibility, and sensitivity to UV light.The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science and Technology (ITN) Linköping University, Campus Norrköping, SE-601 74 Norrköping, Sweden. kamran.ul.hasan@liu.se.

ABSTRACT
Relatively long (30 µm) high quality ZnO nanowires (NWs) were grown by the vapor-liquid-solid (VLS) technique. Schottky diodes of single NW were fabricated by putting single ZnO NW across Au and Pt electrodes. A device with ohmic contacts at both the sides was also fabricated for comparison. The current-voltage (I-V) measurements for the Schottky diode show clear rectifying behavior and no reverse breakdown was seen down to -5 V. High current was observed in the forward bias and the device was found to be stable up to 12 V applied bias. The Schottky barrier device shows more sensitivity, lower dark current, and much faster switching under pulsed UV illumination. Desorption and re-adsorption of much smaller number of oxygen ions at the Schottky junction effectively alters the barrier height resulting in a faster response even for very long NWs. The NW was treated with oxygen plasma to improve the switching. The photodetector shows high stability, reversibility, and sensitivity to UV light. The results imply that single ZnO NW Schottky diode is a promising candidate for fabricating UV photodetectors.

No MeSH data available.


Related in: MedlinePlus