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Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

The Hebrew University of Jerusalem

Gold nanoparticles (Aunano) co-deposited with cobalt hexacyanoferrate (CoHCF) modified electrode was prepared by electrodeposition on glassy carbon electrode (represented as GC/Aunano-CoHCF) and characterized. The surface morphology of the modified electrode was studied by AFM and the electrochemical properties were studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The co-deposition of Aunano with CoHCF improved the electrochemical behavior of the Aunano-CoHCF modified electrode when compared to CoHCF modified electrode. The in-situ spectroelectrochemical changes of Aunano-CoHCF modified electrode was studied to understand the redox switching of CoHCF in the presence of Aunano. The in-situ spectral study showed that the co-deposited Aunano with CoHCF acted as nanoelectrode and improved the electron transfer and redox switching processes when compared to CoHCF modified electrode. An enhanced electrocatalytic oxidation of hydrogen peroxide (H2O2) was observed at the GC/Aunano-CoHCF electrode with an onset potential of 0.5 V when compared to GC/CoHCF electrode. The poly Au electrode did not show a similar oxidation peak for H2O2 oxidation. The Aunano co-deposited with CoHCF (GC/Aunano-CoHCF) significantly enhanced the electrocatalytic property of CoHCF. The amperometric detection of H2O2 was studied at the CoHCF modified electrode in the presence and absence of Aunano and poly Au electrode. The GC/Aunano-CoHCF electrode showed fast sensing response and lower detection limit for H2O2 when compared to GC/CoHCF and poly Au electrode. The electrochemical, in situ spectroelectrochemical and electrocatalytic properties of Aunano co-deposited with CoHCF clearly showed that the GC/Aunano-CoHCF electrode could be used as an electrochemical sensor.

Electrochemical and in situ spectroelectrochemical studies on the gold nanoparticles co-deposited with cobalt hexacyanoferrate modified electrode and its application in sensor.

Multibranched gold (Au) nanocomposite materials encapsulated by poly(o-phenylenediamine) (PoPD) (Au@PoPD) were synthesized in a Nafion polymer film through the electroless synthetic route. The micro-heterogeneous structured Nafion film acted as a reaction vessel and as the template for the formation of Au@PoPD nanocomposite materials leading to the formation of highly uniform distribution of high density of the polymer-gold nanocomposite material. The formation of Au@PoPD nanomaterials at the GP/Nf surface was scrutinized by recording in situ absorption spectra and was characterized. The formation of the (111) plane of gold was dominant at the Au@PoPD nanocomposite. The ratio of the benzenoid and quinoid units of the PoPD (ca. 1.65) observed for the Au@PoPD confirmed that the micro-heterogeneous structure of Nf film acted as a reaction vessel and as template for the formation of Au@PoPD nanocomposite material. Both PoPD and Au at the Au@PoPD nanocomposite showed electrochemical activities at the GC/Nf-Au@PoPD modified electrode. The electrocatalytic activity of the GC/Nf-Au@PoPD modified electrode was studied for oxygen reduction reaction (ORR).

Electroless synthesis of multibranched gold nanostructures encapsulated by poly(o-phenylenediamine) in Nafion.

Contact doping method for the controlled surface doping of silicon wafers and nanometer scale structures is presented. The method, monolayer contact doping (MLCD), utilizes the formation of a dopant-containing monolayer on a donor substrate that is brought to contact and annealed with the interface or structure intended for doping. A unique feature of the MLCD method is that the monolayer used for doping is formed on a separate substrate (termed donor substrate), which is distinct from the interface intended for doping (termed acceptor substrate). The doping process is controlled by anneal conditions, details of the interface, and molecular precursor used for the formation of the dopant-containing monolayer. The MLCD process does not involve formation and removal of SiO(2) capping layer, allowing utilization of surface chemistry details for tuning and simplifying the doping process. Surface contact doping of intrinsic Si wafers (i-Si) and intrinsic silicon nanowires (i-SiNWs) is demonstrated and characterized. Nanowire devices were formed using the i-SiNW channel and contact doped using the MLCD process, yielding highly doped SiNWs. Kelvin probe force microscopy (KPFM) was used to measure the longitudinal dopant distribution of the SiNWs and demonstrated highly uniform distribution in comparison with in situ doped wires. The MLCD process was studied for i-Si substrates with native oxide and H-terminated surface for three types of phosphorus-containing molecules. Sheet resistance measurements reveal the dependency of the doping process on the details of the surface chemistry used and relation to the different chemical environments of the P═O group. Characterization of the thermal decomposition of several monolayer types formed on SiO(2) nanoparticles (NPs) using TGA and XPS provides insight regarding the role of phosphorus surface chemistry at the SiO(2) interface in the overall MLCD process. The new MLCD process presented here for controlled surface doping provides a simple yet highly versatile means for achieving postgrowth doping of nanometer scale structures and interfaces.

Contact doping of silicon wafers and nanostructures with phosphine oxide monolayers.

More than they appear on the surface: The treatment of SiO2 nanoparticles under mild conditions with two organoboron derivatives led to boron-containing monolayers with different types of surface species (see picture) through the direct formation of Si-O-B bonds. The organoboron-modified SiO2 NPs showed selective reactivity towards diols.

Thangavel Subramani

Institute of Chemistry,
Center for Nanoscience and Nanotechnology

The Hebrew University of Jerusalem

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Thangavel Subramani

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Institute of Chemistry,Center for Nanoscience and Nanotechnology

The Hebrew University of Jerusalem

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Institute of Chemistry,
Center for Nanoscience and Nanotechnology