Microstructure and piezoelectric response of Y Al1−N thin films

Mayrhofer, P.H.; Riedl, H.; Euchner, Holger; Stöger-Pollach, Michael; Mayrhofer, Paul H.; Bittner, A.; Schmid, U.

doi:10.1016/j.actamat.2015.08.019

Cited by 72 publications

(63 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The wurzite phase is found to be favorable up to x = 0.25, beyond which rocksalt alloys are stable; this wurzite to rocksalt phase transition point is consistent with previous experimental observations and other theoretical predictions. 19,20 We have compared the mixing enthalpy of the Cr x Al 1−x N alloys with that of several other common wurzite-based nitrides, 13,15,18,36,37 Sc x Al 1−x N, Y x Al 1−x N, and Y x In 1−x N, with the results shown in Figure 2(b). The mixing enthalpies are positive for all cases, meaning that the alloying of AlN or InN with their respective end members is an endothermic process.…”

Section: A Enthalpy Of Mixingmentioning

confidence: 99%

Enhanced Piezoelectric Response of AlN via CrN Alloying

et al. 2018

View full text Add to dashboard Cite

Since AlN has emerged as an important piezoelectric material for a wide variety of applications, efforts have been made to increase its piezoelectric response via alloying with transition metals that can substitute for Al in the wurtzite lattice. Herein, we report density functional theory calculations of structure and properties of the Cr-AlN system for Cr concentrations ranging from zero to beyond the wurtzite-rocksalt transition point. By studying the different contributions to the longitudinal piezoelectric coefficient, we propose that the physical origin of the enhanced piezoelectricity in CrxAl1−xN alloys is the increase of the internal parameter u of the wurtzite structure upon substitution of Al with the larger Cr ions. Among a set of wurtzite-structured materials, we have found that Cr-AlN has the most sensitive piezoelectric coefficient with respect to alloying concentration. Based on these results, we propose that Cr-AlN is a viable piezoelectric material whose properties can be tuned via Cr composition. We support this proposal by combinatorial synthesis experiments, which show that Cr can be incorporated in the AlN lattice up to 30% before a detectable transition to rocksalt occurs. At this Cr content, the piezoelectric modulus d33 is approximately four times larger than that of pure AlN. This finding, combined with the relative ease of synthesis under nonequilibrium conditions, may propel Cr-AlN as a prime piezoelectric material for applications such as resonators and acoustic wave generators.

show abstract

Section: A Enthalpy Of Mixingmentioning

confidence: 99%

Enhanced Piezoelectric Response of AlN via CrN Alloying

et al. 2018

View full text Add to dashboard Cite

show abstract

“…It was also reported that other impurities may cause the same effect. Mayrhofer et al observed a reduction in the preferential (0001) texture and an increase in the surface roughness with increasing Y content in Al(1 − x )Y( x )N films. A general finding between these studies is that the high content of impurity species (which in the case of the present study is Sc) can disrupt growth or nucleation behavior, causing nucleation of AOGs and the loss of the desirable (0001) film texture.…”

Section: Introductionmentioning

confidence: 99%

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

Sandu

Parsapour

Mertin

et al. 2018

Physica Status Solidi (a)

View full text Add to dashboard Cite

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.

show abstract

“…solid solutions between two compounds, have been extensively investigated for use in electromechanical applications. [6][7][8][9][10] Most of these alloys have large miscibility gaps, which makes them less appealing for applications where mechanical stability is an important figure of merit. The presence of miscibility gaps is not particularly restrictive, since current non-equilibrium processing techniques allow for fabricating pseudo-binary alloys in which one can seek a given functionality by, e.g., changing composition (often through the miscibility gaps) so as to optimize piezoelectric coefficients, stiffness, electromechanical coupling constants, or electronic properties.…”

Section: Introductionmentioning

confidence: 99%

“…With the discovery of the anomalously large increase in the piezoelectric moduli of wurtzite AlN when alloyed with ScN 11 or YN, 9,12 AlN-based alloys have received a lot of attention as materials for improved telecommunications, sensors, and surface acoustic wave devices. 13,14 The origin of the enhanced piezoelectricity was revealed to be an intrinsic effect of alloying, as opposed to textural or microstructural effects, 6 with the obvious implication that controlling the piezoelectric enhancement can be done mainly by increasing composition of YN or ScN.…”

Section: Introductionmentioning

confidence: 99%

Tuning the piezoelectric and mechanical properties of the AlN system via alloying with YN and BN

Manna

Brennecka

Stevanović

et al. 2017

Journal of Applied Physics

View full text Add to dashboard Cite

Recent advances in microelectromechanical systems often require multifunctional materials, which are designed so as to optimize more than one property. Using density functional theory calculations for alloyed nitride systems, we illustrate how co-alloying a piezoelectric material (AlN) with different nitrides helps tune both its piezoelectric and mechanical properties simultaneously. Wurtzite AlN-YN alloys display increased piezoelectric response with YN concentration, accompanied by mechanical softening along the crystallographic c direction. Both effects increase the electromechanical coupling coefficients relevant for transducers and actuators. Resonator applications, however, require superior stiffness, thus leading to the need to decouple the increased piezoelectric response from a softened lattice.We show that co-alloying of AlN with YN and BN results in improved elastic properties while retaining some of the piezoelectric enhancements from YN alloying. This finding may lead to new avenues for tuning the design properties of piezoelectrics through composition-property maps.

show abstract

Microstructure and piezoelectric response of Y Al1−N thin films

Cited by 72 publications

References 30 publications

Enhanced Piezoelectric Response of AlN via CrN Alloying

Enhanced Piezoelectric Response of AlN via CrN Alloying

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

Tuning the piezoelectric and mechanical properties of the AlN system via alloying with YN and BN

Contact Info

Product

Resources

About