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Plasmon-Enhanced Surface Photovoltage of ZnO/Ag Nanogratings.

Gwon M, Sohn A, Cho Y, Phark SH, Ko J, Sang Kim Y, Kim DW - Sci Rep (2015)

Bottom Line: SPP excitation influenced the spatial distribution of the photo-excited carriers and their recombination processes.As a result, the SPV relaxation time clearly depended on the wavelength and polarization of the incident light.All of these results suggested that SPV measurement using KPFM should be very useful for studying the plasmonic effects in nanoscale metal/semiconductor hybrid structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Ewha Womans University, Seoul 120750, Korea.

ABSTRACT
We investigated the surface photovoltage (SPV) behaviors of ZnO/Ag one-dimensional (1D) nanogratings using Kelvin probe force microscopy (KPFM). The grating structure could couple surface plasmon polaritons (SPPs) with photons, giving rise to strong light confinement at the ZnO/Ag interface. The larger field produced more photo-excited carriers and increased the SPV. SPP excitation influenced the spatial distribution of the photo-excited carriers and their recombination processes. As a result, the SPV relaxation time clearly depended on the wavelength and polarization of the incident light. All of these results suggested that SPV measurement using KPFM should be very useful for studying the plasmonic effects in nanoscale metal/semiconductor hybrid structures.

No MeSH data available.


(a) Atomic force microscopy (AFM) topography image of the region on the nanograting surface used for the TM-mode SPV measurements. (b) WS map without illumination and (c) WS map under illumination by a TM-mode green light (wavelength: 532 nm) of the region in (a). (d) AFM topography image of the region used for the TE-mode measurements. (e) WS map without illumination and (f) WS map under illumination by a TE-mode green light of the region in (d).
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f2: (a) Atomic force microscopy (AFM) topography image of the region on the nanograting surface used for the TM-mode SPV measurements. (b) WS map without illumination and (c) WS map under illumination by a TM-mode green light (wavelength: 532 nm) of the region in (a). (d) AFM topography image of the region used for the TE-mode measurements. (e) WS map without illumination and (f) WS map under illumination by a TE-mode green light of the region in (d).

Mentions: Figure 2a–f show topography and work-function (WS) maps of the ZnO/Ag nanograting. All of the images were obtained at the top flat region of the grating, because the tip-sample convolution did not allow reliable measurements at the lower part of the grating1920. As shown in Fig. 2a,d, the sample surface has mounds with sizes on the order of tens of nanometers; these mounds are presumed to be grains formed during growth and/or heat treatment before the KPFM measurements. The dark-state WS values are similar to those reported in the literature19 and show spatial fluctuation (Fig. 2b,e). Similar electronic inhomogeneity has also been reported in other KPFM studies of ZnO thin films1920. Doping concentrations and oxygen adsorbates can alter the WS of the ZnO thin films192023. Jaramillo and Ramanathan reported that larger (smaller) WS appeared at the grain boundaries (over the grains) of optimally oxidized ZnO thin films19. A comparison of the topographic images (Fig. 2a,d) and WS maps in the dark (Fig. 2b,e) reveals no clear relationship in the spatial distributions of the grain boundaries and regions with large (or small) WS, similar to the results of Maragliano et al.20. This result suggests that our ZnO thin films could be insufficiently oxidized20. The oxidation state of our samples should be determined by the growth conditions and heat treatment prior to the KPFM measurements.


Plasmon-Enhanced Surface Photovoltage of ZnO/Ag Nanogratings.

Gwon M, Sohn A, Cho Y, Phark SH, Ko J, Sang Kim Y, Kim DW - Sci Rep (2015)

(a) Atomic force microscopy (AFM) topography image of the region on the nanograting surface used for the TM-mode SPV measurements. (b) WS map without illumination and (c) WS map under illumination by a TM-mode green light (wavelength: 532 nm) of the region in (a). (d) AFM topography image of the region used for the TE-mode measurements. (e) WS map without illumination and (f) WS map under illumination by a TE-mode green light of the region in (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645158&req=5

f2: (a) Atomic force microscopy (AFM) topography image of the region on the nanograting surface used for the TM-mode SPV measurements. (b) WS map without illumination and (c) WS map under illumination by a TM-mode green light (wavelength: 532 nm) of the region in (a). (d) AFM topography image of the region used for the TE-mode measurements. (e) WS map without illumination and (f) WS map under illumination by a TE-mode green light of the region in (d).
Mentions: Figure 2a–f show topography and work-function (WS) maps of the ZnO/Ag nanograting. All of the images were obtained at the top flat region of the grating, because the tip-sample convolution did not allow reliable measurements at the lower part of the grating1920. As shown in Fig. 2a,d, the sample surface has mounds with sizes on the order of tens of nanometers; these mounds are presumed to be grains formed during growth and/or heat treatment before the KPFM measurements. The dark-state WS values are similar to those reported in the literature19 and show spatial fluctuation (Fig. 2b,e). Similar electronic inhomogeneity has also been reported in other KPFM studies of ZnO thin films1920. Doping concentrations and oxygen adsorbates can alter the WS of the ZnO thin films192023. Jaramillo and Ramanathan reported that larger (smaller) WS appeared at the grain boundaries (over the grains) of optimally oxidized ZnO thin films19. A comparison of the topographic images (Fig. 2a,d) and WS maps in the dark (Fig. 2b,e) reveals no clear relationship in the spatial distributions of the grain boundaries and regions with large (or small) WS, similar to the results of Maragliano et al.20. This result suggests that our ZnO thin films could be insufficiently oxidized20. The oxidation state of our samples should be determined by the growth conditions and heat treatment prior to the KPFM measurements.

Bottom Line: SPP excitation influenced the spatial distribution of the photo-excited carriers and their recombination processes.As a result, the SPV relaxation time clearly depended on the wavelength and polarization of the incident light.All of these results suggested that SPV measurement using KPFM should be very useful for studying the plasmonic effects in nanoscale metal/semiconductor hybrid structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Ewha Womans University, Seoul 120750, Korea.

ABSTRACT
We investigated the surface photovoltage (SPV) behaviors of ZnO/Ag one-dimensional (1D) nanogratings using Kelvin probe force microscopy (KPFM). The grating structure could couple surface plasmon polaritons (SPPs) with photons, giving rise to strong light confinement at the ZnO/Ag interface. The larger field produced more photo-excited carriers and increased the SPV. SPP excitation influenced the spatial distribution of the photo-excited carriers and their recombination processes. As a result, the SPV relaxation time clearly depended on the wavelength and polarization of the incident light. All of these results suggested that SPV measurement using KPFM should be very useful for studying the plasmonic effects in nanoscale metal/semiconductor hybrid structures.

No MeSH data available.