Erlangen 2018 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 2: Low Pressure Plasmas I

P 2.4: Vortrag

Montag, 5. März 2018, 11:30–11:45, KI 1.174

Reactive magnetron sputtering of Ta-doped SnO₂ polycrystalline films at low temperatures: carrier transport and role of negative ion bombardment — •Stefan Seeger, Klaus Ellmer, Rainald Mientus, and Michael Weise — Optotransmitter-Umweltschutz-Technologie e.V., Köpenicker Str. 325, 12555 Berlin

Tin oxide (SnO₂) is significantly cheaper and chemically more resistive compared to the often used tin-doped indium oxide (ITO). In principle, low resistivities of doped SnO₂ are possible, caused by its isotropic 5s orbitals which are advantageous for good TCO transport properties. In this work conductive and transparent SnO₂:Ta films were deposited at low substrate temperatures by reactive DC and RF magnetron sputtering from a ceramic target (Sn 98at %Ta 2at %O₂) in Ar/O₂ , Ar/N₂O, and H₂O gas mixtures. The films were X-ray amorphous for substrate temperatures below about 200 ^∘C. While the amorphous films are remarkably conductive (5 x 10⁻³ Ωcm), the crystallized films exhibit higher resistivities due to grain boundary limited electrical transport. Also, for larger film thicknesses, caused by the heating of the films by the energy influx from the film species and the plasma, crystallization occurs. The width of the process window with respect to the reactive gas partial pressure depends on the type of the reactive gas and is wider for N₂O and H₂O. A prospective application of such X-ray amorpous SnO₂:Ta films are low temperature transparent and conductive protection layers, for instance to protect semiconducting photoelectrodes for water splitting.