title: Photocurrent polarization anisotropy of randomly oriented nanowire networks.
abstract: While the polarization sensitivity of single or aligned NW ensembles is well-known, this article reports on the existence of residual photocurrent polarization sensitivities in random NW networks. In these studies, CdSe and CdTe NWs were deposited onto glass substrates and contacted with Au electrodes separated by 30-110 microm gaps. SEM and AFM images of resulting devices show isotropically distributed NWs between the electrodes. Complementary high resolution TEM micrographs reveal component NWs to be highly crystalline with diameters between 10 and 20 nm and with lengths ranging from 1 to 10 microm. When illuminated with visible (linearly polarized) light, such random NW networks exhibit significant photocurrent anisotropies rho = 0.25 (sigma = 0.04) [rho = 0.22 (sigma = 0.04)] for CdSe (CdTe) NWs. Corresponding bandwidth measurements yield device polarization sensitivities up to 100 Hz. Additional studies have investigated the effects of varying the electrode potential, gap width, and spatial excitation profile. These experiments suggest electrode orientation as the determining factor behind the polarization sensitivity of NW devices. A simple geometric model has been developed to qualitatively explain the phenomenon. The main conclusion from these studies, however, is that polarization sensitive devices can be made from random NW networks without the need to align component wires.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Yanghai
authors.initials: Y
authors.lastname: Yu
authors.forename: Vladimir
authors.initials: V
authors.lastname: Protasenko
authors.forename: Debdeep
authors.initials: D
authors.lastname: Jena
authors.forename: Huili Grace
authors.initials: HG
authors.lastname: Xing
authors.forename: Masaru
authors.initials: M
authors.lastname: Kuno
mesh_terms: D016880:Anisotropy; D019187:Cadmium Compounds / Q000737:chemistry* / Q000528:radiation effects; D003460:Crystallization / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D004574:Electromagnetic Fields; D008027:Light; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D010777:Photochemistry / Q000379:methods*; D012031:Refractometry / Q000379:methods*; D018036:Selenium Compounds / Q000737:chemistry* / Q000528:radiation effects; D013691:Tellurium / Q000737:chemistry* / Q000528:radiation effects; D014159:Transducers
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D013691:Tellurium; C028337:cadmium telluride