Review: Structural, elastic, and thermodynamic properties of cubic and hexagonal ScxAl1−xN crystals

Abstract

A review of the structural, elastic, and thermodynamic properties of cubic and hexagonal ScxAl1−xN crystals over the range of possible random alloys is provided. Based on measured and simulated lattice and internal cell parameters of NaCl (B1), CsCl (B2), and α-ZnS (B3) type cubic ScxAl1−xN lattices as well as of β-ZnS (B4), lh-MgO (Bk), and NiAs (B81) type hexagonal ScxAl1−xN crystals, their atomic positions, distances to nearest neighbor atoms, geometric dimensions of crystal cells, mass density, as well as their average bond length and bond angles are presented in dependence on the alloy composition. The understanding gained about the crystal lattices is used to provide a model for the transitions from the β-ZnS to the lh-MgO or NaCl lattice induced by the alloying of AlN with ScN. Based on published data sets of stiffness coefficients, the compliance coefficients, Young's modulus, shear modulus, Poisson's ratio, compressibility, and the sound velocities are presented in relation to the orientation of representative crystal planes and axes for rock salt, layered hexagonal, and wurtzite ScxAl1−xN crystals. Particular attention is paid to the directional anisotropies of elastic properties of the different crystal lattices if Sc atoms substitute an increasing number of Al atoms. Based on sound velocities determined, an overview of the fundamental thermodynamic properties of cubic and hexagonal ScxAl1−xN alloys is provided, such as the Debye temperature, heat capacity, minimum heat conduction, and melting temperature.

Local Environment of Sc and Y Dopant Ions in Aluminum Nitride Thin Films

“…A destabilized, mechanically softer lattice is more readily deformed in the presence of an applied stress or electric field. As reviewed by Ambacher et al, the stiffness coefficient C 33 ( x ) decreases due to the alloying of wurtzite-AlN with rock-salt-ScN, but at the same time, the piezoelectric coefficient d 33 ( x ) increases very sharply up to the miscibility limit. This finding is similar to the mechanism suggested for the case of the morphotropic phase boundary (MPB) in solid solutions of PbZrO 3 –PbTiO 3 (PZT), although, unlike (Al, Sc)­N, this system displays full miscibility.…”

Enhancing antioxidant properties of CeO2 nanoparticles with Nd3+ doping: structural, biological, and machine learning insights

“…The variations in the lattice parameters in a solid solution follow Vegard's law, which does not consider structural defects or compressive hydrostatic pressure. 31…”

Ammonothermal Crystal Growth of Functional Nitrides for Semiconductor Devices: Status and Potential

“…More recently, additional polymorphs have been discovered for some of these materials (such as wurtzite and rocksalt MnSnN2 [17]), further widening the design space. In addition, this also opens up the possibility of heteroepitaxial integration of different phases of the same material with distinctly different properties, as O. Ambacher recently contemplated for AlScN [18]. Both the properties of ternary nitrides and their epitaxial relationships to different materials are of interest, as will be elaborated in the following paragraphs.…”

“…The two data points shown for the orthorhombic materials are the wurtzite-equivalent in-plane lattice parameters 𝑎√3 and b/2. Data were obtained from the following references: 6mm-BN [24][25][26], 6mm-AlN [18,[27][28][29], 6mm-GaN [26][27][28][29], 6mm-InN [26][27][28][29], 6mm-MnSnN2 [30], mm2-MgSiN2 [31][32][33][34][35][36], mm2-MgGeN2 [31,[33][34][35][36][37], mm2-MgSnN2 [17,33,34,[38][39][40], mm2-ZnSiN2 [21,23,[41][42][43][44], mm2-ZnGeN2 [21,23,41,42,44], mm2-ZnSnN2 [21,23,40,[44]…”