Sputter deposited ZnO porous films for sensing applications
- PDF / 352,909 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 16 Downloads / 191 Views
Sputter deposited ZnO porous films for sensing applications Michaá A. Borysiewicz1, ElĪbieta Dynowska1,2, Valery Kolkovsky2, Maciej Wielgus1,3, Krystyna Goáaszewska1, Eliana KamiĔska1, Marek Ekielski1, Przemysáaw Struk4, Tadeusz Pustelny4 and Anna Piotrowska1 1 Institute of Electron Technology, Al. Lotników 32/46, 02-668 Warsaw, Poland 2 Institute of Physics, PAS, Al. Lotników 32/46, 02-668 Warsaw, Poland 3 Warsaw University of Technology, Pl. Politechniki 1, 00-661 Warsaw, Poland 4 Silesian University of Technology, ul. Akademicka 2A, 44-100 Gliwice, Poland ABSTRACT Nanoporous ZnO films are fabricated using a two step approach: sputter deposition of porous Zn followed by an ex-situ annealing in an oxygen flow at 400oC. The created structures have a porosity of 34% enabling use in surface-based absorption sensors. The films are used in a resistance-based sensor allowing easy discrimination between liquid methanol and ethanol by resistance measurements and also in a transmission-based sensor to detect NO2, NH3 and H2 gases in concentration as low as 500 ppm. INTRODUCTION Every year, solid-state sensors gain widespread use due to their versatility, ease of tailoring by functionalization and cost-competitiveness. The heart of such a sensor is usually some volume of material to which the sensed species are absorbed. An enhanced surface to volume ratio in the sensing part of such a device can substantially improve their detection performance. The enhancement may be fabricated either through a top-down (dry or wet etching) or bottom-up (nanostructure growth) approaches, the latter of which includes the growth of a wide family of structures from the more common nanowires and nanorods [1] to more exotic flower-like structures [2]. In this report we focus on a cost-effective way of producing a highly porous dendrite-like ZnO film using a method enabling fast coating of large areas for potential large-scale applications, i.e. sputtering and apply it in two model sensor configurations: a resistance-based sensor and a transmission-based sensor. The first one is used to discriminate between two types of alcohols by measuring their resistivity after the application of a set volume to the porous ZnO film. The transmission-based sensor monitors changes in the transmission of the porous ZnO deposited on glass in a dry air environment after the application of set concentrations of contaminating gases such as NO2, NH3 and H2. EXPERIMENT The porous ZnO films were prepared using a two-step method: first, a porous Zn film was grown via reactive magnetron sputtering of a 4N Zn target under 80W DC power in an argon-oxygen mixture with 17% oxygen content in a Surrey NanoSystems Ȗ1000C sputtering system. The total pressure of the gas mixture during deposition was 1.5 mtorr and the base pressure prior to deposition was of the order of 10-7 torr. The second step comprised of ex-situ annealing in an oxygen flow at 400oC, performed in order to form ZnO. A detailed discussion of
71
the growth procedure along with the influence of process param
Data Loading...
