title: Molecular modulation of conductivity on H-terminated silicon-on-insulator substrates.
abstract: The adsorption of a range of molecular species (water, pyridine, and ammonia) is found to reversibly modulate the conductivity of hydrogen-terminated silicon-on-insulator (H-SOI) substrates. Simultaneous sheet-resistance and Hall-effect measurements on moderately doped (10(15) cm(-3)) n- and p-type H-SOI samples mounted in a vacuum system are used to monitor the effect of gas exposure in the Torr range on the electrical-transport properties of these substrates. Reversible physisorption of "hole-trapping" species, such as pyridine (C(5)H(5)N) and ammonia (NH(3)) produces highly conductive minority-carrier channels (inversion) on p-type substrates, mimicking the action of a metallic gate in a field-effect transistor. The adsorption of these same molecules on n-type SOI induces strong electron-accumulation layers. Minority/majority channels are also formed upon controlled exposure to water vapor. These observations can be explained by a classical band-bending model, which considers the adsorbates as the source of a uniform surface charge ranging from +10(11) to +10(12)q cm(-2). These results demonstrate the utility of DC transport measurements of SOI platforms for studies of molecular adsorption and charge-transfer effects at semiconductor surfaces.
authors.affiliation: Steacie Institute for Molecular Sciences, National Research Council, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6, Canada.
authors.forename: Girjesh
authors.initials: G
authors.lastname: Dubey
authors.forename: Federico
authors.initials: F
authors.lastname: Rosei
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Lopinski
mesh_terms: D000327:Adsorption; D004553:Electric Conductivity; D011725:Pyridines / Q000737:chemistry; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D011725:Pyridines; D014867:Water; C023666:pyridine; D012825:Silicon