title: Semiconductor-Metal Nanofloret Hybrid Structures by Self-Processing Synthesis.
abstract: We present a synthetic strategy that takes advantage of the inherent asymmetry exhibited by semiconductor nanowires prepared by Au-catalyzed chemical vapor deposition (CVD). The metal-semiconductor junction is used for activating etch, deposition, and modification steps localized to the tip area using a wet-chemistry approach. The hybrid nanostructures obtained for the coinage metals Cu, Ag, and Au resemble the morphology of grass flowers, termed here Nanofloret hybrid nanostructures consisting of a high aspect ratio SiGe nanowire (NW) with a metallic nanoshell cap. The synthetic method is used to prepare hybrid nanostructures in one step by triggering a programmable cascade of events that is autonomously executed, termed self-processing synthesis. The synthesis progression was monitored by ex situ transmission electron microscopy (TEM), in situ scanning transmission electron microscopy (STEM) and inductively coupled plasma mass spectrometry (ICP-MS) analyses to study the mechanistic reaction details of the various processes taking place during the synthesis. Our results indicate that the synthesis involves distinct processing steps including localized oxide etch, metal deposition, and process termination. Control over the deposition and etching processes is demonstrated by several parameters: (i) etchant concentration (water), (ii) SiGe alloy composition, (iii) reducing agent, (iv) metal redox potential, and (v) addition of surfactants for controlling the deposited metal grain size. The NF structures exhibit broad plasmonic absorption that is utilized for demonstrating surface-enhanced Raman scattering (SERS) of thiophenol monolayer. The new type of nanostructures feature a metallic nanoshell directly coupled to the crystalline semiconductor NW showing broad plasmonic absorption.
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Ori
authors.initials: O
authors.lastname: Hazut
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Sharon
authors.initials: S
authors.lastname: Waichman
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Thangavel
authors.initials: T
authors.lastname: Subramani
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Sarkar
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Sthitaprajna
authors.initials: S
authors.lastname: Dash
authors.affiliation: Department of Physics, University of York , Heslington, York YO10 5DD, United Kingdom.
authors.forename: Teresa
authors.initials: T
authors.lastname: Roncal-Herrero
authors.affiliation: Department of Physics, University of York , Heslington, York YO10 5DD, United Kingdom.
authors.forename: Roland
authors.initials: R
authors.lastname: Kröger
authors.affiliation: Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.
authors.forename: Roie
authors.initials: R
authors.lastname: Yerushalmi