title: A 30 μm Coaxial Nanowire Photoconductor Enabling Orthogonal Carrier Collection.
abstract: We describe the preparation and properties of a coaxial, three-layer, gold-CdSe-gold nanowire 30 μm in length that functions as a monolithic photodetector. The gold (Au) electrode core of this sandwich structure is prepared using the lithographically patterned nanowire electrodeposition (LPNE) method on a glass surface. A CdSe shell of defined thickness, dCdSe, from 200 to 280 nm is then electrodeposited on this Au nanowire. Finally, a conformal gold layer is electrodeposited on top of the CdSe shell. The two concentric gold electrodes within this architecture measure the photoconductivity of the ultrathin CdSe absorbing layer in the direction orthogonal to the nanowire axis. This architecture enables accelerated response/recovery of the nanowire to light while simultaneously maximizing the photoconductive gain without relinquishing any of the photoresponsive area of a "bare" nanowire. Characterization by scanning electron microscopy (SEM) of focused ion beam (FIB) cross sections together with electron dispersive X-ray spectroscopy (EDS) reveal the distinct core-multishell nanostructure, layer thicknesses, and layer compositions. The position-dependent photoresponse along the axis of the nanowire, probed using a laser spot, shows that the Au nanoshell significantly enhances the photocurrent. The performance of Au-CdSe-Au core-multishell nanowire photodetectors depend sensitively on the thickness of CdSe nanoshell over the range of from 200 nm < dCdSe < 280 nm. The highest performance was obtained for the dCdSe = 250 nm this device, which showed a photoconductive gain of 2172, a responsivity of 209 A·W(-1), a response time of 17 μs, and a recovery time of 96 μs.
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.|Department of Physics, Xiamen University , Xiamen 361005, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697, United States.
authors.forename: Shaopeng
authors.initials: S
authors.lastname: Qiao
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697, United States.
authors.forename: Rajen
authors.initials: R
authors.lastname: Dutta
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.
authors.forename: Mya
authors.initials: M
authors.lastname: Le Thai
authors.affiliation: Department of Chemical Engineering and Materials Sciences, University of California , Irvine, California 92697, United States.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.
authors.forename: Crystin J
authors.initials: CJ
authors.lastname: Eggers
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.
authors.forename: Girija Thesma
authors.initials: GT
authors.lastname: Chandran
authors.affiliation: Department of Physics, Xiamen University , Xiamen 361005, China.
authors.forename: Zhengyun
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Department of Chemistry, University of California , Irvine, California 92697, United States.|Department of Chemical Engineering and Materials Sciences, University of California , Irvine, California 92697, United States.
authors.forename: Reginald M
authors.initials: RM
authors.lastname: Penner
keywords: Multishell; cadmium selenide; electrodeposition; gain; photoconductor; photodetector; responsivity