Full Length ArticleIn-situ XRD vs ex-situ vacuum annealing of tantalum oxynitride thin films: Assessments on the structural evolution
Introduction
Tantalum (Ta) thin films and tantalum ceramic thin films (oxides, nitrides and oxynitrides) have extraordinary properties allowing them to be used in several interesting applications. Tantalum (refractory metal with melting temperature around 3050 °C) and tantalum nitride can be used as resistors and heaters, in the case of Ta, but also diffusion barriers, pressure sensors and protective layers [1], [2], [3], [4], [5], [6], [7]. Particularly, the formation of a tantalum oxide layer on the surface of Ta or Ta-nitrides allows them to have high resistance to chemical attacks [2].
The potential of these materials as thin films to be used in high temperature applications is significant. Several publications can be found where the behaviour of tantalum and tantalum nitride films under annealing is studied. To the best of our knowledge, the number of studies referring the behaviour of tantalum oxynitride subjected to thermal treatments is limited. The authors have published a study about the structural stability of a set of tantalum oxynitride films [8], while J.H. Hsieh et al. [9] discussed the behaviour of TaNxOy thin films with and without rapid thermal annealing.
Generally, concerning the structural stability with the temperature of any material, most of the studies follow the same pattern: annealing execution, generally in vacuum, followed by structural evaluation, normally by XRD, at room temperature. Only a few studies refer to the study of the structure evolution, obtaining the XRD patterns at specific temperatures, simultaneously with the annealing process. In this work, the differences concerning the structural evolution of magnetron sputtered TaNxOy films are discussed, after vacuum annealing, in two conditions: the diffraction patterns were captured at room temperature, after vacuum annealing, and compared to in-situ annealing and structural evaluation by XRD.
Section snippets
Experimental details
TaNxOy thin films were deposited onto silicon (100) substrates by DC reactive magnetron sputtering. Before being inserted in the chamber, the substrates were cleaned with ethanol. Prior to the etching process and subsequent deposition, the chamber was evacuated to a base pressure of 1.1÷1.3 × 10−3 Pa. The substrates were plasma etched for a period of 500 s, using pure argon with a partial pressure of ∼0.3 Pa (60 sccm) and a pulsed current of approximately 0.6 A.
The substrate holder was positioned at 70
Tantalum oxynitride film produced with (N + O)/Ta ≈ 0.1 (P(N2 + O2) = 0.02 Pa (B1))
The Ta content of the B1 film is around 90 at.% (Table 2). Fig. 1 reveals the XRD pattern of the as-deposited sample and of the samples that suffered ex-situ annealing at 400 °C, 600 °C and 800 °C. The XRD pattern of the as-deposited samples evidences a quasi-amorphous structure with evidences of poorly developed β–Ta or Ta2N crystallites, revealed by a broad peak, in the range 33° < 2θ < 42°. The peak detected at 2θ = 36.1°, may be assigned to the (410) planes of the β–Ta structure or, more probably, to
Conclusions
TaNxOy thin films were deposited by magnetron sputtering. The structural evolution as function of the annealing temperature was studied under two different conditions: i) vacuum annealing, at specific temperatures, and registration of XRD patterns at room temperature after annealing (ex-situ process); ii) vacuum annealing, at specific temperatures, and registration of XRD patterns at those specific temperatures (in-situ process). The general observations of the structural behaviour of the
Acknowledgement
This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013.
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A stable and plug-and-play aluminium/titanium dioxide/metal-organic framework/silver composite sheet for sensitive Raman detection and photocatalytic removal of 4-aminothiophenol
2021, ChemosphereCitation Excerpt :In Fig. 3B and C, the weak peaks at 2θ = 23.7°, 66.5°, and 78.4° are observed, which are consistent with (021), (440), and (533) planes of Al2O3 (JCPDS No: 46–1215), respectively. From curve a to b, the main peaks shift towards large angle because of lattice shrinkage caused by doping of oxygen atoms and increased compressive stress resulting from TiO2 coating (Henke et al., 2012; Cunha et al., 2018). From curve c to d, these peaks shift towards small angle, which could be attributed to the lattice expansion by doping of zinc ions and/or increased tensile stress by ZIF-8 coating (Li et al., 2019; Xie et al., 2016).