Phonon engineering in isotopically disordered silicon nanowires
The introduction of stable isotopes in the fabrication of semiconductor nanowires provides an additional degree of freedom to manipulate their basic properties, design an entirely new class of devices, and highlight subtle but important nanoscale and quantum phenomena. With this perspective, we repo...
| Autores: | , , , , , , , , , , , |
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| Formato: | artículo |
| Fecha de publicación: | 2015 |
| País: | España |
| Recursos: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglés |
| OAI Identifier: | oai:ddd.uab.cat:200188 |
| Acesso em linha: | https://ddd.uab.cat/record/200188 https://dx.doi.org/urn:doi:10.1021/acs.nanolett.5b00708 |
| Access Level: | acceso abierto |
| Palavra-chave: | Atom probe tomography Nanowires Phonons Raman spectroscopy Stable isotopes Thermal conductivity |
| Resumo: | The introduction of stable isotopes in the fabrication of semiconductor nanowires provides an additional degree of freedom to manipulate their basic properties, design an entirely new class of devices, and highlight subtle but important nanoscale and quantum phenomena. With this perspective, we report on phonon engineering in metal-catalyzed silicon nanowires with tailor-made isotopic compositions grown using isotopically enriched silane precursors ²⁸SiH, ²⁹SiH, and ³⁰SiH with purity better than 99.9%. More specifically, isotopically mixed nanowires ²⁸Si ³⁰Si with a composition close to the highest mass disorder (x ∼ 0.5) were investigated. The effect of mass disorder on the phonon behavior was elucidated and compared to that in isotopically pure Si nanowires having a similar reduced mass. We found that the disorder-induced enhancement in phonon scattering in isotopically mixed nanowires is unexpectedly much more significant than in bulk crystals of close isotopic compositions. This effect is explained by a nonuniform distribution of ²⁸Si and ³⁰Si isotopes in the grown isotopically mixed nanowires with local compositions ranging from x = ∼0.25 to 0.70. Moreover, we also observed that upon heating, phonons in ²⁸Si ³⁰Si nanowires behave remarkably differently from those in ²⁹Si nanowires suggesting a reduced thermal conductivity induced by mass disorder. Using Raman nanothermometry, we found that the thermal conductivity of isotopically mixed ²⁸Si Si nanowires is ∼30% lower than that of isotopically pure ²⁹Si nanowires in agreement with theoretical predictions. (Figure Presented). |
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