"Covalently attached Monolayers on crystalline Hydrogen-terminated Silicon"

CECILIA I. VÁZQUEZ; BERNARDA QUIROGA ARGAÑARAZ; GABRIELA I. LACCONI

La Palma, Islas Canarias, España

Congreso; 2nd ECHEMS Meeting "Electrochemistry in Surface Functionalization"; 2006

ECHEMS

Organic monolayers are an emerging area of research in nanoelectronics [1]. Possible future applications of these molecular layers include organic transistors, sensors in biochemistry and biophysics and hybrid silicon-molecular memory applications (in flash or dynamic random access memory) [2,3]. Other (perhaps, more immediate) applications include passivation, patterning, and control of the chemical and physical properties of interfaces [4]. Determination of the electrical properties of the interfaces between the organic monolayers and the semiconductor substrates, particularly charge trapping at and charge transport across the silicon/organic interfaces, are key issues common to all the above applications of molecular nanoelectronics. Also common to the success of these applications is the realization of a stable, densely packed, organic monolayer, covalently bonded directly to the silicon surface [5-7]. The purpose of this work was the formation and characterization of hidrogen-terminated Si(111) surfaces derivatized with covalently attached alkyl chains and aromatic alkyl monolayers. The synthesis of the monolayers was performed using neat 1-octadecene or styrene, which react efficiently with the hydrogen-terminated Si(111) when heated at temperatures over 140ºC or under exposition to UV radiation (λ = 254 nm). The monolayer formation reactions are assumed to be a radical-based process thermally or photochemically induced, that starts at a defect (e.g., a dangling bond) at the H-terminated surface. The electrochemical charaterization of the organically functionalized silicon surface was performed by cyclic voltammetry and electrochemical impedance, related to its ability to inihibit the oxide formation. Direct correlations between the coverage and the electrical properties of the film with the potential for the silicon oxide electroformation are established. The structural characterization of the surfaces derivatized through covalent Si-C linkages was performed by ex-situ AFM and STM.