Design of Metastable Tin Titanium Nitride Semiconductor Alloys

Bikowski, André; Siol, Sebastian; Gu, Jing; Holder, Aaron M.; Mangum, John S.; Gorman, Brian P.; Tumas, William; Lany, Stephan; Zakutayev, Andriy

doi:10.1021/acs.chemmater.7b02122

Cited by 30 publications

(22 citation statements)

References 70 publications

(102 reference statements)

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“…The libraries were subdivided into four rows and 11 columns in which the composition varied across columns and the substrate deposition temperature varied across rows. More information about the deposition chamber used in these experiments can be found in prior publications [55].…”

Section: B Experimentsmentioning

confidence: 99%

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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Section: B Experimentsmentioning

confidence: 99%

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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“…More information about the deposition system used in this set of experiments can be found elsewhere. [40,41] The deposition and characterization data will be made available at https://htem.nrel.gov, an open access experiential data repository. [42] Particular care was taken to limit the sources of oxygen in the lanthanum tungsten oxynitride thin films.…”

Section: Methodsmentioning

confidence: 99%

“…The films were subdivided using a shadow mask into individual samples in which the La:W ratio varied, which could be correlated between measurements. More information about the deposition system used in this set of experiments can be found elsewhere . The deposition and characterization data will be made available at https://htem.nrel.gov, an open access experiential data repository …”

Section: Methodsmentioning

confidence: 99%

Synthesis of Lanthanum Tungsten Oxynitride Perovskite Thin Films

Talley

Mangum

Perkins

et al. 2019

Adv Elect Materials

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Ternary metal‐oxide material systems commonly crystallize in the perovskite crystal structure, which is utilized in numerous electronic applications. In contrast to oxides, there are no known nitride perovskites, likely due to the competition with oxidation, which makes the formation of pure nitride materials difficult and synthesis of oxynitride materials more common. While deposition of oxynitride perovskite thin films is important for many electronic applications, it is difficult to control oxygen and nitrogen stoichiometry. Lanthanum tungsten oxynitride (LaWN3−δOδ) thin films with varying La:W ratio are synthesized by combinatorial sputtering and characterized for their chemical composition, crystal structure, and microstructure. A three‐step synthesis method, which involves co‐sputtering, capping layer deposition, and rapid thermal annealing, is established for producing crystalline thin films while minimizing the oxygen content. Elemental depth profiling results show that the cation‐stoichiometric films contain approximately one oxygen for every five nitrogen (δ = 0.5). Synchrotron‐based diffraction indicates a tetragonal perovskite crystal structure. These results are discussed in terms of the perovskite tolerance factors, octahedral tilting, and bond valence. Overall, this synthesis and characterization is expected to pave the way toward future thin film property measurements of lanthanum tungsten oxynitrides and eventual synthesis of oxygen‐free nitride perovskites.

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“…In an effort to accelerate the discovery and development of advanced materials computational data from first principles has been made available for many materials systems in online repositories, including W-Ti-O 19 . Recently, high-throughput combinatorial experiments have been used for an accelerated screening of synthesis-phase-diagrams in a variety of material systems [21][22][23][24][25] . This type of phase diagram screening is typically performed using non-equilibrium physical vapor deposition (PVD) techniques 25,26 , which often results in homogeneous alloy samples with high miscibility 27,28 .…”

Section: Introductionmentioning

confidence: 99%