Formation of Molecular Templates Containing Cumulative Double Bonds (CCC) at Organic/Silicon Hybrid Interfaces

ORGANIC-SILICON INTERFACE

A review of the performances of existing field-effect-transistor (FET) based biosensing devices and reports of fundamental studies of FET structures in a planar geometry identify substantial amplification improvements in eliminating metal intermediaries between the biorecognitive surfaces and the silicon channels, reducing thicknesses of insulating gates and selecting channel apertures that are comparable with achievable thicknesses of depletion layers. Exemplary improvements have been achieved in FET-based silicon nano-wires in which biorecognitive surfaces were attached to the oxidized surfaces that functioned as insulating gates. Fundamental studies in which the silicon dioxide gate was replaced with an organic layer using Si – C chemistry demonstrate the retention of the field-effect characteristics and promise improved performance potential to present FET-based devices. These studies also report electrical field compression of the organic layer and electrical polarisation of the electrolyte that have operational implications for biorecognition. Development of practical robust devices that can exhibit unambiguous recognitive capabilities in diverse biological aquatic environments is dependent on further extensive fundamental studies of organic-silicon interfaces and bio-recognitive processes.

Selective attachment of benzaldehyde on Si(100)-2×1: Structure, selectivity, and mechanism

The interaction of benzaldehyde with the Si(100) surface has been investigated as a model system for understanding the interaction of conjugated pi-electron systems with semiconductor surfaces. Vibrational features of chemisorbed benzaldehyde unambiguously demonstrate that the carbonyl group directly interacts with the Si surface dangling bonds, evidenced in the disappearance of the C=O stretching mode around 1713 cm(-1) coupled with the retention of all vibrational signatures of its phenyl ring. X-ray photoemission spectroscopy shows that both C 1s and O 1s binding energies of the carbonyl group display large downshifts by 1.9 and 1.3 eV, respectively. Vibrational and electronic results show that the covalent attachment of benzaldehyde on Si(100) occurs in a highly selective manner through the direct interaction of both C and O atoms of the carbonyl group with a Si=Si dimer to form a four-membered Si-C-O-Si ring at the interface, leaving a nearly unperturbed phenyl ring protruding into vacuum. This conclusion is further confirmed by the observation of a predominant protrusion for benzaldehyde adsorbed on Si(100)-2 x 1 in scanning tunneling microscopy experiments, consistent with the predication of density-functional theory calculation.