Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices
Systematic results of lattice dynamical calculations are reported as a function of m and n for the novel (SiC)<sub>m</sub>/(GeC)<sub>n</sub> superlattices (SLs) by exploiting a modified linear-chain model and a realistic rigid-ion model (RIM). A bond polarizability method is...
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Multidisciplinary Digital Publishing Institute
2023
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| Online Access: | https://hdl.handle.net/1721.1/153235 |
| _version_ | 1811084931327066112 |
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| author | Talwar, Devki N. Becla, Piotr |
| author2 | Massachusetts Institute of Technology. Department of Materials Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Materials Science and Engineering Talwar, Devki N. Becla, Piotr |
| author_sort | Talwar, Devki N. |
| collection | MIT |
| description | Systematic results of lattice dynamical calculations are reported as a function of m and n for the novel (SiC)<sub>m</sub>/(GeC)<sub>n</sub> superlattices (SLs) by exploiting a modified linear-chain model and a realistic rigid-ion model (RIM). A bond polarizability method is employed to simulate the Raman intensity profiles (RIPs) for both the ideal and graded (SiC)<sub>10-Δ</sub>/(Si<sub>0.5</sub>Ge<sub>0.5</sub>C)<sub>Δ</sub>/(GeC)<sub>10-Δ</sub>/(Si<sub>0.5</sub>Ge<sub>0.5</sub>C)<sub>Δ</sub> SLs. We have adopted a virtual-crystal approximation for describing the interfacial layer thickness, Δ (≡0, 1, 2, and 3 monolayers (MLs)) by selecting equal proportions of SiC and GeC layers. Systematic variation of Δ has initiated considerable upward (downward) shifts of GeC-(SiC)-like Raman peaks in the optical phonon frequency regions. Our simulated results of RIPs in SiC/GeC SLs are agreed reasonably well with the recent analyses of Raman scattering data on graded short-period GaN/AlN SLs. Maximum changes in the calculated optical phonons (up to ±~47 cm<sup>−1</sup>) with Δ = 3, are proven effective for causing accidental degeneracies and instigating localization of atomic displacements at the transition regions of the SLs. Strong Δ-dependent enhancement of Raman intensity features in SiC/GeC are considered valuable for validating the interfacial constituents in other technologically important heterostructures. By incorporating RIM, we have also studied the phonon dispersions [<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><msubsup><mrow><msub><mrow><mi mathvariant="sans-serif">ω</mi></mrow><mrow></mrow></msub></mrow><mrow><mi mathvariant="normal">j</mi></mrow><mrow><mi mathvariant="normal">S</mi><mi mathvariant="normal">L</mi></mrow></msubsup></mrow><mrow></mrow></msub><mfenced separators="|"><mrow><mover accent="true"><mrow><mi mathvariant="bold">q</mi></mrow><mo>→</mo></mover></mrow></mfenced></mrow></semantics></math></inline-formula>] of (SiC)<sub>m</sub>/(GeC)<sub>n</sub> SLs along the growth [001] as well as in-plane [100], [110] directions [i.e., perpendicular to the growth]. In the acoustic mode regions, our results of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><msubsup><mrow><msub><mrow><mi mathvariant="sans-serif">ω</mi></mrow><mrow></mrow></msub></mrow><mrow><mi mathvariant="normal">j</mi></mrow><mrow><mi mathvariant="normal">S</mi><mi mathvariant="normal">L</mi></mrow></msubsup></mrow><mrow></mrow></msub><mfenced separators="|"><mrow><mover accent="true"><mrow><mi mathvariant="bold">q</mi></mrow><mo>→</mo></mover></mrow></mfenced><mo> </mo></mrow></semantics></math></inline-formula> have confirmed the formation of mini-gaps at the zone center and zone edges while providing strong evidences of the anti-crossing and phonon confinements. Besides examining the angular dependence of zone-center optical modes, the results of phonon folding, confinement, and anisotropic behavior in (SiC)<sub>m</sub>/(GeC)<sub>n</sub> are compared and contrasted very well with the recent first-principles calculations of (GaN)<sub>m</sub>/(AlN)<sub>n</sub> strained layer SLs. |
| first_indexed | 2024-09-23T13:00:18Z |
| format | Article |
| id | mit-1721.1/153235 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T13:00:18Z |
| publishDate | 2023 |
| publisher | Multidisciplinary Digital Publishing Institute |
| record_format | dspace |
| spelling | mit-1721.1/1532352024-01-24T21:57:10Z Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices Talwar, Devki N. Becla, Piotr Massachusetts Institute of Technology. Department of Materials Science and Engineering Systematic results of lattice dynamical calculations are reported as a function of m and n for the novel (SiC)<sub>m</sub>/(GeC)<sub>n</sub> superlattices (SLs) by exploiting a modified linear-chain model and a realistic rigid-ion model (RIM). A bond polarizability method is employed to simulate the Raman intensity profiles (RIPs) for both the ideal and graded (SiC)<sub>10-Δ</sub>/(Si<sub>0.5</sub>Ge<sub>0.5</sub>C)<sub>Δ</sub>/(GeC)<sub>10-Δ</sub>/(Si<sub>0.5</sub>Ge<sub>0.5</sub>C)<sub>Δ</sub> SLs. We have adopted a virtual-crystal approximation for describing the interfacial layer thickness, Δ (≡0, 1, 2, and 3 monolayers (MLs)) by selecting equal proportions of SiC and GeC layers. Systematic variation of Δ has initiated considerable upward (downward) shifts of GeC-(SiC)-like Raman peaks in the optical phonon frequency regions. Our simulated results of RIPs in SiC/GeC SLs are agreed reasonably well with the recent analyses of Raman scattering data on graded short-period GaN/AlN SLs. Maximum changes in the calculated optical phonons (up to ±~47 cm<sup>−1</sup>) with Δ = 3, are proven effective for causing accidental degeneracies and instigating localization of atomic displacements at the transition regions of the SLs. Strong Δ-dependent enhancement of Raman intensity features in SiC/GeC are considered valuable for validating the interfacial constituents in other technologically important heterostructures. By incorporating RIM, we have also studied the phonon dispersions [<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><msubsup><mrow><msub><mrow><mi mathvariant="sans-serif">ω</mi></mrow><mrow></mrow></msub></mrow><mrow><mi mathvariant="normal">j</mi></mrow><mrow><mi mathvariant="normal">S</mi><mi mathvariant="normal">L</mi></mrow></msubsup></mrow><mrow></mrow></msub><mfenced separators="|"><mrow><mover accent="true"><mrow><mi mathvariant="bold">q</mi></mrow><mo>→</mo></mover></mrow></mfenced></mrow></semantics></math></inline-formula>] of (SiC)<sub>m</sub>/(GeC)<sub>n</sub> SLs along the growth [001] as well as in-plane [100], [110] directions [i.e., perpendicular to the growth]. In the acoustic mode regions, our results of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><msubsup><mrow><msub><mrow><mi mathvariant="sans-serif">ω</mi></mrow><mrow></mrow></msub></mrow><mrow><mi mathvariant="normal">j</mi></mrow><mrow><mi mathvariant="normal">S</mi><mi mathvariant="normal">L</mi></mrow></msubsup></mrow><mrow></mrow></msub><mfenced separators="|"><mrow><mover accent="true"><mrow><mi mathvariant="bold">q</mi></mrow><mo>→</mo></mover></mrow></mfenced><mo> </mo></mrow></semantics></math></inline-formula> have confirmed the formation of mini-gaps at the zone center and zone edges while providing strong evidences of the anti-crossing and phonon confinements. Besides examining the angular dependence of zone-center optical modes, the results of phonon folding, confinement, and anisotropic behavior in (SiC)<sub>m</sub>/(GeC)<sub>n</sub> are compared and contrasted very well with the recent first-principles calculations of (GaN)<sub>m</sub>/(AlN)<sub>n</sub> strained layer SLs. 2023-12-22T15:34:55Z 2023-12-22T15:34:55Z 2023-10-01 2023-12-22T13:45:01Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/153235 Solids 4 (4): 287-303 (2023) PUBLISHER_CC http://dx.doi.org/10.3390/solids4040018 Creative Commons Attribution https://creativecommons.org/licenses/by/4.0/ application/pdf Multidisciplinary Digital Publishing Institute Multidisciplinary Digital Publishing Institute |
| spellingShingle | Talwar, Devki N. Becla, Piotr Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title | Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title_full | Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title_fullStr | Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title_full_unstemmed | Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title_short | Evaluating Phonon Characteristics by Varying the Layer and Interfacial Thickness in Novel Carbon-Based Strained-Layer Superlattices |
| title_sort | evaluating phonon characteristics by varying the layer and interfacial thickness in novel carbon based strained layer superlattices |
| url | https://hdl.handle.net/1721.1/153235 |
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