AVS 60th International Symposium and Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP11
Towards the Heat Dissipation in Suspended Self-heated Nanowire Sensors

Tuesday, October 29, 2013, 6:00 pm, Room Hall B

Session: Nanometer-scale Science and Technology Poster Session
Presenter: J. Zhang, Southern Illinois University Carbondale
Authors: J. Zhang, Southern Illinois University Carbondale
E. Strelcov, Oak Ridge National Laboratory
A. Kolmakov, Southern Illinois University Carbondale
Correspondent: Click to Email
Self-heating is a prospective power-efficient energy delivery channel to the conductometric chemical sensors that require elevated temperatures for their operation. Strong temperature dependence of the electrical conductivity in semiconductors was employed with a self-heated n-doped silicon nanowire resistor whose surfaces were passivated with native oxide layer. The conductivity in such a device depends on heat dissipation and partitioning inside the device what was studied comparatively for both suspended and supported device architectures. The onset of the exhaustion region in the temperature-dependent resistivity of a Joule-heated nanowire was used as a temperature marker for implementation of the quasi-constant temperature operation mode. As the thermal conductivity of the environment around the nanowire changing upon analyte admission into the chamber, the semiconductor nanowire temperature changes and as a result, an electrical conductivity alters as well. In such a case a nanowire is inert toward the used analytes, the sensing action due to analyte-induced heat dissipation variations can be extracted. Our approach is close to the effort to create membrane-based ultra-sensitive Pirani type thermal pressure sensor with significantly enlarged pressure range and very recent nanowire Pirani gauge. At low pressures, the sensor is idle due to dominating heat dissipation from the nanowire to the substrate and/or electrodes. Above ca 10 Torr the sensitivity to gases has strong dependence on pressure as well as type of the gas and is determined by heat exchange between nanowire surface and ambient. Unlike classical Pirani sensors, we found that the sensitivity of this nanowire pressure sensor does not exhibit the saturation behavior at subatmospheric pressure thanks to nanoscopic size of the nanowire and microchannel architecture of the device. Additionally, the sensitivity of the sensor to reactive gases depends on the effectiveness of the particular endothermic/exothermic reaction at the surface of the nanowires and was explored for the case of acetone-air mixture with Pt decorated silicon nanowire devices suspended across ca 20 um wide trench of Si/SiO2 substrate. Strong coupling of the electrical and thermal properties in the individual Joule heated semiconducting nanowire allows fabrication of power-efficient multi-parametric nanoscopic gas/pressure sensors that are analog of Pirani and pellistor type detectors.