Phase-field modeling of nanostructural evolution in physical vapor deposited phase-separating ternary alloy films

Abstract

Self-assembly by spinodal decomposition is known to be a viable route for synthesizing nanoscaled interfaces in a variety of materials, including metamaterials. In order to tune the response of these specialized materials to external stimuli, knowledge of processing-nanostructure correlations is required. Such an understanding is more challenging to obtain purely by experimental means due to complexity of multicomponent atomic diffusion mechanisms that govern the nanostructural self-assembly. In this work, we introduce a phase-field modeling approach which is capable of simulating the nanostructural evolution in ternary alloy films that are typically synthesized using physical vapor deposition. Based on an extensive parametric study, we analyze the role of the deposition rate and alloy composition on the nanostructural self-assembly in ternary alloy films. The simulated nanostructures are categorized on the basis of nanostructured morphology and mapped over a compositional space to correlate the processing conditions with the film nanostructures. The morphology maps reveal that while deposition rate governs the nanostructural evolution at around equi-molar compositions, the impact of composition on nanostructuring is more pronounced when the atomic ratios of alloying elements are skewed.

Density Functional Theory-Fed Phase Field Model for Semiconductor Nanostructures: The Case of Self-Induced Core–Shell InAlN Nanorods

“…To simulate deposition, an additional layer of noisy concentration field (which preserves the overall composition of elements in the domain) is deposited on the nanorods every 15Δ t . We would like to clarify that the chosen value of deposition rate corresponds to the simulation of phase separating nanostructures with lateral concentration modulations that has been reported in our previous work . The nanorod height is allowed to increase until 260Δ x as the phase separation continues.…”

“…We would like to clarify that the chosen value of deposition rate corresponds to the simulation of phase separating nanostructures with lateral concentration modulations that has been reported in our previous work. 7 The nanorod height is allowed to increase until 260Δx as the phase separation continues.…”

“…Once this procedure for calculation of the interfacial energy for interfaces consisting of wurtzite binary compounds is established and judged reliable enough, it can be employed for the determination of the interface energies between ternary InAlN compounds that more closely reproduce the composition of typical cores and shells of experimentally verified selfinduced NRs. 18 In Table 1, the interfacial energies for typical interfaces that are particularly relevant to the experimental results are reported, namely, (i) Al(0.75)In(0.25)N (indium rich core) versus Al(0.98)In(0.02)N (indium poor shell) 7 The values of the interfacial energies (Table 1) depend nonlinearly on phase compositions and vary significantly as a function of the core/shell compositions. Qualitative analysis indicates that lower interfacial energy values tend to be obtained for interfaces which have .…”

“…While the interfacial energies and the ratios of atomic diffusion constants selected for phase field simulations are based on DFT simulations, the remaining parameters tabulated in Table 3 are chosen based on our prior knowledge on phase separation in ternary alloy films nanostructures. 7 It is to be noted in such systems that, during the sputtering of phaseseparating ternary alloy films, the resulting nanostructures can vary significantly depending on factors such as composition, deposition rate, and temperature (which influence atomic mobility). These variations can lead to distinct nanostructured variants, including those with lateral concentration modulations (LCM), vertical concentration modulations (VCM), and structures with random bicontinuous, core−shell, or globular morphologies.…”

“…For the latter, PFM has been successfully applied to study the formation mechanism of the core−shell (C−S) structures obtained by sintering of spherical nanoparticles. 10 While the PFM has been already conceptually developed with the nanostructural evolution in PVD-grown phaseseparating ternary alloy films, 7 it has not yet been applied to simulate the evolution of experimentally demonstrated selfinduced semiconductor nanostructures. This aspect, together with the idea to feed the PFM by parameters obtained via sophisticated DFT calculations, is the motivation for our present work on demonstrating the capabilities of PFM simulations for understanding the formation of group IIIA nitride ternary nanostructures.…”