(103a) Alkyl Functionalized Silicon Surfaces
AIChE Annual Meeting
Monday, November 9, 2009 - 12:30pm to 12:50pm
Silicon is one of the most abundant semiconductor materials on our planet. The (100) oriented Si wafers are used extensively in the microelectronics industry. The formation of a 40 nm thick native oxide on the surface however deteriorates the excellent electronic properties of silicon. Si-C termination is known to provide passivation towards the native oxide formation. Organic monolayers are electrografted onto the silicon in order to passivate the surface towards the formation of this native oxide. Here, cathodic electrografting of phenyl acetylene and hexynoic acid and anodic electrografting of methyl and ethyl Grignards upon (100) silicon surfaces are demonstrated. The cyclic voltammetry behavior of the organic monolayers being electrografted is investigated. Silicon/organic monolayer surface chemistry is investigated using AFM and FTIR techniques. The XPS results indicate methyl monolayer termination provides stable Si-C termination upon (100) silicon for ~50 days in ambient air as shown in Figure below. Nanopatterns of organic monolayers (phenyl acetylene/methyl) are also reported upon (100) Si surfaces to provide stability and passivation towards electroplating of copper and additional means of design flexibility. Electrochemical impedance spectroscopy (EIS) is used to obtain the charge transfer characteristics during the metal electrodeposition process. Hexynoic acid termination is successfully used to immobilize Bovine Serum Albumin (BSA) protein via EDC chemistry. The immobilized protein is further detected by fluorescence spectroscopy and EIS technique. Silicon could act as a potential lithium ion storage device with a high theoretical capacity. The recent research pathways using Silicon nanowires instead of silicon indicate capacities of 90% of the theoretical possibility mainly due to the higher porosity and higher surface area/volume ratio. The results however indicate capacity fading after certain number of charging/discharging cycles. The organic functionalization is expected to reduce this capacity fading eliminating the silicon oxide formation acting as an impurity causing the fade, thus increasing the performance of the lithium ion batteries. Silicon is also an established semiconductor material in the field of photovoltaics with a commercially viable efficiency of 24%. Despite its photo conversion efficiency, silicon could not be incorporated in a PEC cell for Hydrogen production using sunlight. Photoelectrochemical effects are investigated for organic monolayer functionalized silicon surfaces. The work indicates the initial, but potential studies of evolution of SiNWs in both these fields suggesting the problems yet to be overcome using the technique of passivation via electrografting alkyl monolayers.
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