Nanoscale Characterization of Metal/Semiconductor Nanocables
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1080-O03-12
Nanoscale Characterization of Metal/Semiconductor Nanocables Ruxandra Vidu1, Brian E McCandless2, Jeff Berkheimer3, David J Duval4, and Pieter Stroeve4 1 R&D, Bloo Solar, 2545 Boatman Ave, West Sacramento, CA, 95691 2 Institute of Energy Conversion, 451 Wyoming Road, Newark, DE, 19716 3 Bloo Solar, 2545 Boatman Ave, West Sacramento, CA, 95691 4 University of California, Davis, CA, 95616 ABSTRACT Comprehensive characterization at nanoscale is needed to create novel nanostructures for high efficiency solar cells. To produce consistent results, wide-ranging characterization procedures for integrated nanostructures have been developed. Characterization of a novel nanowire, nanotube and nanocable system includes: chemical, electrochemical, structural, optical and electrical characterization of nanostructures in relation with growth conditions. We present here results on Au and CdTe/Au system that help understanding how surface composition and properties are modified in this system. New challenges in structural characterization were also identified and improved sample preparation techniques were developed. INTRODUCTION The search for viable renewable energy sources opened the door to new materials and structures for high-efficiency solar cells. Particularly, developments in nanotechnology within the renewable energy industry have the potential to create significant advances for the renewable energy industry. This work is part of the project that seeks to establish necessary conditions to create novel nanostructures for high efficiency solar cells. To produce consistent results, comprehensive characterization procedures for integrated nanostructures have been developed. Some of the challenges associated with nanoscale characterization are presented. EXPERIMENTAL DETAILS Electrochemical characterization of the nanostructured electrodes was performed in a conventional three-electrode setup consisting of a computer operated potentiostat (VersaStat II, Princeton Applied Research). The reference electrode was a Ag/AgCl electrode (3 M NaCl). All potentials are given here relative to the Ag/AgCl (0.194 V vs NHE). The counter electrode was an Au wire. Electrolyte was purged with N2 for at least 15 minutes before each run. A Scintag XDS 2000 diffractometer was used to collect the XRD patterns using CuKα radiation (l = 1.540562 Å) to determine degree of preferred orientation and lattice parameter of grains oriented normal to the substrate plane. Software housing all current JCPDS data was used to analyze the X-ray diffraction patterns and identify various phases that are present. Structural characterization was performed using Scanning Electron Microscope (SEM) model XL30-SFEG, a high-resolution scanning electron microscope capable of resolutions better than 2 nm, magnifications over 600 kX, and operating voltages from 200 volts up to 30 kV. We routinely used 5 kV and 10 kV. At lower beam potentials of 5 kV, we obtained excellent
topographic detail and minimum charging while at the higher potentials we performed effic
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