Tuning the electrical properties of Si nanowire field-effect transistors by molecular engineering.
Exposed facets of n-type silicon nanowires (Si NWs) fabricated by a top-down approach are successfully terminated with different organic functionalities, including 1,3-dioxan-2-ethyl, butyl, allyl, and propyl-alcohol, using a two-step chlorination/alkylation method. X-ray photoemission spectroscopy and spectroscopic ellipsometry establish the bonding and the coverage of these molecular layers. Field-effect transistors fabricated from these Si NWs displayed characteristics that depended critically on the type of molecular termination. Without molecules the source-drain conduction is unable to be turned off by negative gate voltages as large as -20 V. Upon adsorption of organic molecules there is an observed increase in the "on" current at large positive gate voltages and also a reduction, by several orders of magnitude, of the "off" current at large negative gate voltages. The zero-gate voltage transconductance of molecule-terminated Si NW correlates with the type of organic molecule. Adsorption of butyl and 1,3-dioxan-2-ethyl molecules improves the channel conductance over that of the original SiO(2)-Si NW, while adsorption of molecules with propyl-alcohol leads to a reduction. It is shown that a simple assumption based on the possible creation of surface states alongside the attachment of molecules may lead to a qualitative explanation of these electrical characteristics. The possibility and potential implications of modifying semiconductor devices by tuning the distribution of surface states via the functionality of attached molecules are discussed.
Bashouti
Muhammad Y
MY
The Department of Chemical Engineering and Russell Berrie Nanotechnology Institute Technion - Israel Institute of Technology, Haifa, Israel.
Tung
Raymond T
RT
Haick
Hossam
H
D002616:Chemical Engineering; D055590:Electromagnetic Phenomena; D008956:Models, Chemical; D036103:Nanotechnology; D053770:Nanowires / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D012825:Silicon / Q000737:chemistry*
D012825:Silicon