| AVS 61st International Symposium & Exhibition | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE+NS+TR-TuM |
| Session: | Nanostructured Thin Films and Coatings |
| Presenter: | Julia Sell, University of Maine |
| Authors: | J.C. Sell, University of Maine D.M. Stewart, University of Maine G.P. Bernhardt, University of Maine D.J. Frankel, University of Maine R.J. Lad, University of Maine |
| Correspondent: | Click to Email |
Considerable cost savings could be achieved by incorporating high temperature sensors into high temperature machinery to optimize processes and monitor materials degradation. However, in order to achieve reliable sensor operation, the thin film electrodes, sensing elements, and packaging materials must remain stable over long times at high temperature. Metallic thin films, such as Pt, agglomerate and lose conductive pathways quickly when exposed to temperatures exceeding 700°C. In this work, we show that Pt-ZrB2 nanocomposite films retain a continuous morphology and remain electrically conductive up to at least 1100oC in air. Nanolaminate Pt-ZrB2 films comprised of ten alternating layers of Pt and ZrB2 were deposited to a total thickness of 200nm at ambient temperature onto sapphire substrates using e-beam evaporation. Annealing the nanolaminate films above 800oC in air causes intermixing, resulting in a nanocomposite Pt-ZrB2 film architecture. Film electrical conductivities were measured using a 4-point probe as a function of time and temperature in air up to 1200°C. These results show that Pt-ZrB2 nanocomposite films have conductivities in the 106-107 S/m range and remain stable above 1000°C, but that the overall conductivity and stability depends on the Pt-ZrB2 layer thickness ratio. Analysis via x-ray photoelectron spectroscopy and x-ray diffraction indicates that both monoclinic and tetragonal ZrO2 nanocrystallites are formed in the films during the annealing treatment, and they serve to hinder agglomeration of the Pt phase. Scanning electron microscopy shows highly conductive Pt-rich pathways in the films that coexist with the ZrO2 phase. Some films were coated with an amorphous Al2O3 protective capping layer using atomic layer deposition (ALD), and this capping layer helped to limit oxygen diffusion into the films, thereby increasing the long term stability of film conductivity.