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Cross-sectional bright-field TEM images from monolithic (MON) and modulated (MOD) TiO 2 :Cr,N coatings as-deposited (AD) (a) and after FLA (b). The slightly under-focused (UF) bright-field images in the third row are magnified views of the marked regions close to the substrate-coating interface in the MOD case to enhance the contrast of the pore structures. Corresponding representative SAED patterns displayed in the bottom part confirm the dominant rutile and anatase character for MON and MOD coatings, respectively.
Source publication
In this paper, we report on the phase selectivity in Cr and N co-doped TiO2 (TiO2:Cr,N) sputtered films by means of interface engineering. In particular, monolithic TiO2:Cr,N films produced by continuous growth conditions result in the formation of a mixed-phase oxide with dominant rutile character. On the contrary, modulated growth by starting wit...
Contexts in source publication
Context 1
... impact of FLA on the film morphology and phase structure was also studied by TEM analysis. Figure 6 shows cross-sectional bright-field TEM images of the monolithic and modulated architecture with a gradient profile. In both samples, there is a thin (~2 nm) SiO 2 layer at the substrate-coating interface coming from the native oxide of the Si(100) wafers. ...
Context 2
... presence of pores in the early stage of growth can also be seen in both samples, although they are more evident in the TiO 2 :N buffer layer within the modulated design. Such pore structures can be resolved more clearly in slightly under-focused (UF) bright-field TEM images, as shown in Figure 6 from a magnified view of the film-substrate interface region. It is also relevant that those structures increase in size after FLA. ...
Context 3
... UF images also emphasize the enhancement (darker zones) of the film crystalline quality near the substrate interface after FLA. Finally, selected-area electron diffraction (SAED) analysis shown in Figure 6 from the imaged regions supports the phase formation derived from XANES and XRD, with a dominant rutile or anatase character for monolithic and modulated coatings, respectively. ...
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Citations
... The paper "Phase Selectivity in Cr and N Co-Doped TiO 2 Films by Modulated Sputter Growth and Post-Deposition Flash-Lamp-Annealing" by Gago et al. presents how the interface engineering strategy can vary the phase occurrence in Cr and N co-doped TiO 2 (TiO 2 :Cr,N) sputter-deposited films [24]. A post-deposition flash-lamp-annealing (FLA) is also used to favor anatase phase, and to give rise to dopant activation and diffusion. ...
This Special Issue contains a series of reviews and papers representing some recent results and some exciting perspectives focused on advanced strategies in thin films growth, thin films engineering by magnetron sputtering and related techniques. Innovative fundamental and applied research studies are then reported, emphasizing correlations between structuration process parameters, new ideas and approaches for thin films engineering and resulting properties of as-deposited coatings.
The impact of Ta incorporation (up to ∼21 at.%) in titanium dioxide (TiO2) films subjected to post-deposition millisecond-range flash-lamp annealing (FLA) is addressed. Phase formation with short-range information was established by means of soft X-ray absorption near-edge structure (XANES) in combination with standard X-ray diffraction. As-grown films are X-ray amorphous, but display a significant structural improvement upon FLA. Up to relatively large Ta concentrations (∼ 12 at.%), FLA can be used to effectively incorporate Ta into a nanocrystalline anatase TiO2 phase, although its structural quality deteriorates progressively with the Ta content. For the intermediate Ta range between 12 and 17 at.%, the structure of the FLA films is highly disordered, being unable to overcome the initial distorted arrangement. In any case, rutile- or Ta2O5-like environments emerge for low and high contents, respectively. Finally, for the highest Ta content (∼21 at.%), the Ta2O5 phase is dominant with an increased quality after FLA. As assessed by XANES, the structural evolution upon FLA seems to be determined by the initial (amorphous) structure. Lastly, all the samples are highly transparent from the visible to the near-infrared region, and the band-gap can be tailored from ∼3.2 to ∼3.8 eV with increasing the amount of incorporated Ta.
