AVS 59th Annual International Symposium and Exhibition
    Electronic Materials and Processing Friday Sessions
       Session EM+NS-FrM

Invited Paper EM+NS-FrM1
Electrical Transport on Chemically Modified Silicon-on-Insulator Substrates

Friday, November 2, 2012, 8:20 am, Room 14

Session: Low-Resistance Contacts to Nanoelectronics
Presenter: G.P. Lopinski, National Research Council of Canada
Correspondent: Click to Email
Electrical transport of semiconductor surfaces and nanostructures are strongly influenced by interfacial processes. Adsorption and reaction events which result in charge re-distribution can modulate conductivity through long-range electric field effects. These effects are being exploited to tailor electronic properties of nanomaterials and devices as well as in the development of electrically-based chemical and biological sensors. Silicon-on-insulator(SOI) substrates, in which the top layer is thinner than the depletion length, are particularly well-suited for demonstrating and investigating the effects of surface processes on electrical transport. Measurements on hydrogen terminated H-SOI substrates (with both (100) and (111) orientations) have demonstrated that adsorption of certain polar molecules (water, pyridine and ammonia) results in large reversible increases in conductivity, attributed to charge transfer effects which induce accumulation of majority carriers on n-type and minority carrier channels (inversion) on p doped substrates. Adsorption of the prototypical electron acceptor tetracyanoethylene (TCNE) results in a strong decrease in conductivity on n-type substrates due to depletion of majority carriers. This effect is not fully reversible due to reactions of TCNE with the H-terminated surface. Use of SOI substrates also facilitates formation of point contact pseudo-MOSFETs, allowing transistor characteristics to be obtained without the need for device fabrication. This approach has been shown to be a simple and straightforward way to monitor the effect of adsorption and reactionevents on the electronic properties of the silicon substrate. Pseudo-MOSFET measurements have been used to monitor surface reactions such as ambient oxidation of the H-terminated surface. Gas phase photochemical reaction of alkenes has been used to chemically passivate these surfaces while maintaining a low density of electrically active defects (<1x1011 cm-2). These alkyl monolayer passivated SOI surfaces show a large reversible response to TCNE, suggesting they can function as good ultrathin gate dielectrics for sensing applications.