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Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.

Zhou H, Fang G, Liu N, Zhao X - Nanoscale Res Lett (2011)

Bottom Line: In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively.For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism.Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronic Science and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China. gjfang@whu.edu.cn.

ABSTRACT
Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

No MeSH data available.


The I-V curves of the PDs with different metal oxide coatings. (a) Before annealing; (b) after annealing at 300°C.
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Figure 2: The I-V curves of the PDs with different metal oxide coatings. (a) Before annealing; (b) after annealing at 300°C.

Mentions: In our experiment, the as-prepared ZnO NRs grow vertically and closely packed on the ZnO seed layer, the gap between ZnO nanowires is very little, and the average diameter and length of these ZnO NRs are around 90-150 nm and 1.4 μm. The I-V curves of the PDs with ZnO seed layer are shown in Figure 2a. From the curves, the plots of I vs. V are straight lines for ZnO seed layer, showing that the contacts at the Pt/ZnO NRs or the Pt/metal oxide interfaces are ohmic. Figure 2b shows the I-V curves of the PDs annealed at 300°C with ZnO seed layer. It can be seen that when the PDs are annealed at 300°C, the Schottky contacts are obtained. Also, after the annealing process, the dark current of PDs decreases greatly. It has been reported that the as-grown ZnO NRs have large defect concentration, which can be improved by thermal annealing [10]. The authors think that the contacts at the electrode/as-prepared ZnO NRs interface are normally ohmic, which is due to the existence of many defects, such as oxygen vacancies or zinc interstitials, resulting in high carrier density, so that the formation of Schottky contacts is very hard, even with the contacts between as-prepared ZnO NRs and electrodes with high work function metals, such as Au, Ni, and Pt. When ZnO NRs are annealed at certain temperatures, the defects will be reduced, and the defect-related carrier density will also decrease, so that the Schottky contact barrier will be formed.


Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.

Zhou H, Fang G, Liu N, Zhao X - Nanoscale Res Lett (2011)

The I-V curves of the PDs with different metal oxide coatings. (a) Before annealing; (b) after annealing at 300°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211197&req=5

Figure 2: The I-V curves of the PDs with different metal oxide coatings. (a) Before annealing; (b) after annealing at 300°C.
Mentions: In our experiment, the as-prepared ZnO NRs grow vertically and closely packed on the ZnO seed layer, the gap between ZnO nanowires is very little, and the average diameter and length of these ZnO NRs are around 90-150 nm and 1.4 μm. The I-V curves of the PDs with ZnO seed layer are shown in Figure 2a. From the curves, the plots of I vs. V are straight lines for ZnO seed layer, showing that the contacts at the Pt/ZnO NRs or the Pt/metal oxide interfaces are ohmic. Figure 2b shows the I-V curves of the PDs annealed at 300°C with ZnO seed layer. It can be seen that when the PDs are annealed at 300°C, the Schottky contacts are obtained. Also, after the annealing process, the dark current of PDs decreases greatly. It has been reported that the as-grown ZnO NRs have large defect concentration, which can be improved by thermal annealing [10]. The authors think that the contacts at the electrode/as-prepared ZnO NRs interface are normally ohmic, which is due to the existence of many defects, such as oxygen vacancies or zinc interstitials, resulting in high carrier density, so that the formation of Schottky contacts is very hard, even with the contacts between as-prepared ZnO NRs and electrodes with high work function metals, such as Au, Ni, and Pt. When ZnO NRs are annealed at certain temperatures, the defects will be reduced, and the defect-related carrier density will also decrease, so that the Schottky contact barrier will be formed.

Bottom Line: In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively.For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism.Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Electronic Science and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China. gjfang@whu.edu.cn.

ABSTRACT
Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (Dλ*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.

No MeSH data available.