Colloidal Silver Nanoparticle Induced Photoluminescence Quench on the Surface Functionalized Planar Si
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Colloidal Silver Nanoparticle Induced Photoluminescence Quench on the Surface Functionalized Planar Si Li-Lin Tay1, Nelson Rowell1, Rabah Boukherroub2 1 National Research Council, Ottawa, Ontario Canada K1A 0R6 2 Interdisciplinary Research Institute (IRI), Avenue Poincaré – BP 69, 59652 Villeneuve d'Ascq, France ABSTRACT The photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) was investigated in the presence of colloidal Ag nanoparticles. The acid passivated Si surface has a weak PL at 1125 nm. Upon exposure to a Ag nanoparticle sol, the PL quenched exponentially with a characteristic decay time of ~ 18 minutes. It is known that the metal mediated charge-transfer process provides a pathway for energy decay and leads to a quenching of luminescence in light emitting material. An in-situ study of the surface passivated Si revealed that the Ag nanoparticle was likely to have come into contact or was sited close enough to the semiconductor surface through adsorption to cause effective PL quenching.
INTRODUCTION The indirect bandgap of bulk Si makes its light emission quite inefficient. Planar Si, however, does exhibit a weak room temperature luminescence signature in the near infrared region from the carrier recombination effect. Light is produced from conduction and valence band carrier recombination. This room temperature bulk Si photoluminescence (PL) can be excited with an Ar laser and the signal detected with a sensitive Ge detector. Planar Si acts as a versatile growth surface for a host of nanostructured materials, e.g. as a template for carbon nanotube growth. Furthermore, metal nanoparticles are often deposited on planar Si surface as possible catalytic materials. Here we examine the change in the PL from surface functionalized planar Si due to an in-situ deposition or adsorption of colloidal Ag nanoparticles.
EXPERIMENTAL DETAILS Double-side polished (100) oriented p-type silicon wafers (boron-doped, 1-15 ohm cm resistivity) were first cleaned in a piranha solution (3:1 (v/v) concentrated H2SO4/30% H2O2) for 15 min at 80 °C and then rinsed copiously with deionized water. The cleaned wafer was then dipped in a 5% HF solution to remove the surface oxides and to passivate the surface with Si-H bonds. Surface functionalization of planar Si was carried out photochemically by placing the hydrogen-terminated Si wafer in a deoxygenated undecylenic solution in a Schlenk tube and exposing the sample to UV radiation (300 nm) for 3 hours. The excess unreacted and physisorbed reagent was removed by rinsing, at room temperature, with tetrahydrofuran and 1,1,1-trichloroethane. The samples were then gently dried under a stream of nitrogen gas. To confirm successful functionalization of monolayer undecylenic acid on planar Si (Si:COOH) had occurred, the Si:COOH surfaces were characterized by attenuated total reflection Fourier
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transform infrared spectroscopy (ATR-FTIR). The PL intensity of Si:COOH was first monitored for one hour in deio
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