title: Hydrogen gas sensors from polysilicon nanobelt devices selectively modified with sensing materials.
abstract: Double-junction n+/n-/n+polysilicon nanobelts featuring selectively deposited sensing materials have been investigated for application as H2gas sensors. The selective modification of the devices was performed through a combination of localized ablation of a resist and lift-off of a previous catalyst material deposited through e-beam evaporation. Four nanobelt devices, differentiated by their doping concentrations at the n-region (from 2.5 × 1013to 2.5 × 1014cm-2), were analyzed in terms of the responses to H2and their self-heating effects. A low doping concentration improved the response at room temperature, owing to a longer Debye length. The variation in the H2-induced surface potential associated with temperature, accounting for degradation in the response of the nanobelts with Joule heating bias, was analyzed in terms of the I-V characteristics of the double-junction device. Among various catalysts (Pt, Pd, Pt/Pd) evaluated for their H2sensing characteristics, an ultrathin film of Pt/Pd was most favorable.
authors.affiliation: Department of Materials Science and Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30050, Taiwan.
authors.forename: Nhan Ai
authors.initials: NA
authors.lastname: Tran
authors.forename: Fu-Ming
authors.initials: FM
authors.lastname: Pan
authors.forename: Jeng-Tzong
authors.initials: JT
authors.lastname: Sheu