Understanding non-stochiometric deposition of multi-principal elemental NiCoCr thin films

[Display omitted] •Multi-principal elemental NiCoCr thin films are successfully fabricated using the pulsed laser deposition route.•The average atomic percentages of Ni and Cr are twice as high as the Co in the as-deposited thin films, whereas the constituent elements are distributed in equiatomic p...

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Published in:Applied surface science 2023-06, Vol.623 (C), p.157011, Article 157011
Main Authors: Mandal, Soumya, Kumar Gupta, Ashish, Rose, Volker, Wieghold, Sarah, Shirato, Nozomi, Sachan, Ritesh
Format: Article
Language:English
Subjects:
Electron microscopy
Multi-principal elemental alloys
NiCoCr
Pulsed laser deposition
Thin films
X-ray absorption spectroscopy
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Summary:[Display omitted] •Multi-principal elemental NiCoCr thin films are successfully fabricated using the pulsed laser deposition route.•The average atomic percentages of Ni and Cr are twice as high as the Co in the as-deposited thin films, whereas the constituent elements are distributed in equiatomic proportion in the ablated NiCoCr target.•The difference in the average atomic percentages of the constituent elements (Ni, Co, and Cr) is explained based on their optical properties (refractive index (n) and extinction coefficient (k)), and vapor pressure. Multi-principal elemental NiCoCr thin films with compositional flexibility have potential applications as a thermal barrier, corrosion-resistant coatings, and functional energy materials. In this study, the non-stochiometric multi-principal element alloy thin film formation behavior from an equiatomic ablation target of NiCoCr using pulsed laser deposition has been reported. Here, the effect of varying laser fluence on compositions of constituent elements in the NiCoCr thin films is systematically investigated. The increase in laser fluence typically increases the likelihood of acquiring undesirable particulates in thin films. Therefore, to maintain the film quality the laser fluences are adjusted within the range of 1.3–3.3 J·cm−2, while the film thicknesses are kept constant at ∼30 nm. Results show that the constituent elements are well-distributed in the formed NiCoCr thin films, however, having average atomic percentages of Ni and Cr twice as high as Co irrespective of the equiatomic composition of individual elements in the ablation target. This stochiometric alteration in the as-deposited thin films is governed by the rate of ablation and subsequent evaporation of each element, which is facilitated by the optical properties and vapor pressure of individual constituent elements. Additionally, electron energy-loss spectroscopy and x-ray absorption spectroscopy analysis reveal that the thin films have partially oxidized, with the Cr oxidation contributing the most to the O-K edge in comparison to Ni and Co. This study presents a laser-assisted pathway for fabricating compositionally flexible NiCoCr thin films and develops an understanding of the non-equilibrium laser-material interactions and how the intrinsic properties of constituent elements affect the stoichiometric flow of materials from the target to the final film deposition.
ISSN:0169-4332
1873-5584
DOI:10.1016/j.apsusc.2023.157011