Effect of scandium content on structure and piezoelectric properties of AlScN films deposited by reactive pulse magnetron sputtering

Zywitzki, O.; Modes, T.; Barth, S.; Bartzsch, Hagen; Frach, Peter

doi:10.1016/j.surfcoat.2016.11.083

Cited by 78 publications

(39 citation statements)

References 14 publications

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“…Their orientation varies with respect to the substrate plane, in contrast to the situation when a competing texture nucleates directly on the substrate. A reduction of the c ‐axis texture in AlScN films with increasing Sc content was also observed in TEM investigations by Zywitzki et al, which supports our observations of AOGs nucleating in later stage of film growth.…”

Section: Resultssupporting

confidence: 92%

“…The observed decrease of the piezoelectric coefficients e 31,f and d 33,f with increased density of AOGs is simply due to the loss of (0001) film orientation. The observation that substrate temperatures below 300 °C produce AlScN films having less losses could explain the fact that the higher temperature will promote segregation of Sc at the GBs, because of the higher mobility of the ad‐atoms. Diffusion activation by ion impact combined with sufficiently low‐energetic barriers at grain boundaries are essential to obtain a sufficient surface diffusion across grain boundaries in order to create and maintain a uniform and compact c ‐axis texture of the wurtzite structure.…”

Section: Resultsmentioning

confidence: 99%

“…Fichtner et al concluded that their number increases with increasing Sc concentration, which we found as well when comparing films made with similar growth conditions. However, no evidence for a cause or mechanism due to the increase of Sc was presented by Fichtner et al, nor by Zywitzki et al when they reported a reduction in (0001) texture with increasing Sc content in AlScN films. They also have not reported on compositional details and the accumulation of Sc at specific sites.…”

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Abnormal Grain Growth in AlScN Thin Films Induced by Complexion Formation at Crystallite Interfaces

Sandu

Parsapour

Mertin

et al. 2018

Physica Status Solidi (a)

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Sputter deposited Al (1-x) Sc x N thin films with a Sc content from x ¼ 0 to 43 at% are investigated by electron microscopy in order to study and explain the formation and growth of abnormally oriented grains (AOG). It is found that the latter did not nucleate at the interface with the substrate, but at high energy grain boundaries, at which systematically higher Sc concentrations are detected. The AOGs are thus formed during the growth of c-textured grains. They grow faster than those, and finally protrude from the c-textured film surface, having at their end a pyramidal shape with three facets of a hexagonal wurtzite crystal: one (0001) and two (11 20) facets. Process conditions favoring less compact grain boundaries, and lower surface diffusion across grain boundaries are thought to promote nucleation of AOGs. Finally, a 4-step growth mechanism explaining the nucleation from a Sc-rich complexion and proliferation of AOGs with increasing film thickness is proposed.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Abnormal Grain Growth in AlScN Thin Films Induced by Complexion Formation at Crystallite Interfaces

Sandu

Parsapour

Mertin

et al. 2018

Physica Status Solidi (a)

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show abstract

“…The results qualitatively agree with previous calculations of the elastic properties [35,37,62,63] and piezoelectric properties [35,37], while simultaneously extending the range of alloy space examined, which is necessary to accurately determine the decoupled nature of the responses. The results agree with the observed softening [22,64] and enhanced piezoelectric strain values [31,[65][66][67] of compositions studied in the literature. It should be noted that many methods are used in these measurements and reliable methods are just now being developed [63,64,68].…”

Section: A Computationsupporting

confidence: 91%

“…• C, films with less than roughly 40% ScN content exhibit a single-phase wurtzite structure, while those with greater than roughly 65% ScN exhibit a single-phase rocksalt structure, in agreement with previous studies [4,67,69,70]. Films of intermediate compositions contain a mixture of both wurtzite and rocksalt phases.…”

Section: B Experimentssupporting

confidence: 90%

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Talley

Millican

Mangum

et al. 2018

Phys. Rev. Materials

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An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (Al 1−x Sc x N) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, and therefore composition-and structuredependent mechanisms, underlying property evolution in this system have not been fully described, despite significant recent efforts driven by interest in enhanced piezoelectric performance. Practical realization of these enhanced properties, however, is hindered by the strong driving thermodynamic driving force for phase separation in the system, highlighting the need for increased study into the role of heterostructural alloying on the thermodynamics and composition-structure-property relationships in this system. With this need in mind, ab initio computed alloy thermodynamics and properties are compared to combinatorial thin-film synthesis and characterization to develop a more complete picture of the structure and property evolution across the Al 1−x Sc x N composition space. The combination of structural frustration and a flattened free-energy landscape lead to substantial increases in electromechanical response. The energy scale of alloy metastability is found to be much larger than previously reported, helping to explain difficulties in achieving homogeneous materials with high scandium concentration. Scandium substitution for aluminum softens the wurtzite crystal lattice, and energetic proximity to the competing hexagonal boron-nitride structure enhances the piezoelectric stress coefficient. Overall, this work provides insight into the understanding of the structure-processing-property relationships in the Al 1−x Sc x N system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.

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Piezoelectric Coefficients and Crystallographic Symmetry

Gorfman,

Zhang

2024

Piezoelectric Materials

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Effect of scandium content on structure and piezoelectric properties of AlScN films deposited by reactive pulse magnetron sputtering

Cited by 78 publications

References 14 publications

Abnormal Grain Growth in AlScN Thin Films Induced by Complexion Formation at Crystallite Interfaces

Abnormal Grain Growth in AlScN Thin Films Induced by Complexion Formation at Crystallite Interfaces

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Piezoelectric Coefficients and Crystallographic Symmetry

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