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Basic properties mapping of anodic oxides in the hafniumniobiumtantalum ternary system
AuthorMardare, Andrei Ionut ; Mardare, Cezarina Cela ; Kollender, Jan Philipp ; Huber, Silvia ; Hassel, Achim Walter
Published in
Science and Technology of Advanced Materials, 2018, Vol. 19, Issue 1, page 554-568
PublishedTaylor & Francis, 2018
Document typeJournal Article
Keywords (EN)Combinatorial libraries / high-throughput experimentation / scanning droplet cell microscopy / anodic oxide films / valve metals
URNurn:nbn:at:at-ubl:3-1114 Persistent Identifier (URN)
 The work is publicly available
Basic properties mapping of anodic oxides in the hafniumniobiumtantalum ternary system [2.78 mb]
Abstract (English)

A thin film combinatorial library deposited by co-sputtering of Hf, Nb and Ta was employed to characterise fundamental properties of the Hf-Nb-Ta system. Compositional mappings of microstructure and crystallography revealed similarities in alloy evolution. Distinct lattice distortion was observed upon addition of hexagonal Hf, leading to amorphisation of alloys containing more than 32 at.% Hf and less than 27 and 41 at.% Nb and Ta, respectively. Volta potential and open circuit potential mappings indicated minimal values for the highest Hf concentration. Localised anodisation of the library by scanning droplet cell microscopy revealed valve metal behaviour. Oxide formation factors above 2 nm V1 were identified in compositional zones with high amounts of Nb and Ta. Fitting of electrochemical impedance spectroscopy data allowed electrical permittivity and resistivity of mixed oxides to be mapped. Their compositional behaviours were attributed to characteristics of the parent metal alloys and particularities of the pure oxides. MottSchottky analysis suggested n-type semiconductor properties for all HfNbTa oxides studied. Donor density and flat-band potential were mapped compositionally, and their variations were found to be related mainly to the Nb amount. Synergetic effects were identified in mappings of Hf-Nb-Ta parent metals and their anodic oxides.

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