The transfer of charge carriers, photogenerated in nanoparticles (NPs), into a single nanowire (NW) is demonstrated in this study by conducting a careful comparison of the optoelectronic characteristics of a ZnO NW with ZnO NPs attached to its surface, a bare ZnO NW and a film of close-packed ZnO NPs. Under the illumination of an above-gap light, the photocurrent taken from the NW with the NPs is remarkably higher in magnitude than that obtained from the bare NW, although the photocurrent is substantially lower for the close-packed NPs. The presence of the absorption band of the NPs in the photoresponse spectrum taken from the NW with the NPs reveals that the transfer of the charge carriers photogenerated in the NPs into the NW dramatically enhances the magnitude of the photocurrent flowing in this NW. Nevertheless, during the transfer, the charge carriers experience trapping and detrapping at the interfaces of the NPs and the NW.
We demonstrate a pn heterojunction diode constructed with a n-type ZnO nanowire (NW) and a p-type HgTe nanoparticle (NP) thin film on a SiO2/p-Si substrate. For the pn heterojunction diode, the rectifying characteristics of both the dark current and the photocurrent excited by 633 nm wavelength light were observed, but the photocurrent excited by 325 nm wavelength light possesses Ohmic characteristics. The optoelectronic characteristics of the pn heterojunction diode were compared with those of the ZnO NW and HgTe NP thin film composing it.
The photocurrent characteristics of HgTe nanoparticle (NP) thin films fabricated on glass substrates were investigated under the illumination of 1.3 µm wavelength light in this work. The photocurrent obtained from an NP thin film with a vertical structure was 119 µA in magnitude at an applied voltage of 2 V. The magnitude of the photocurrent for an NP thin film with a lateral structure was 23.8 nA at 10 V. Nevertheless, the relative magnitude of the photocurrent measured as a function of the chopping frequency was largely the same for the thin films with both the lateral and the vertical structures. The frequency-dependent photocurrent mechanism of the NP thin films will be discussed in detail in this paper.
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