Field induced decrystallization of silicon: Evidence of a microwave non-thermal effect

Nozariasbmarz, Amin; Dsouza, Kelvin; Vashaee, Daryoosh

doi:10.1063/1.5020192

Cited by 29 publications

(19 citation statements)

References 35 publications

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“…In another independent experiment involving MWR heating of a single crystal of silicon, which was partially covered with metallic foils, the authors observed that the exposed part of silicon became amorphous, whereas the covered region remained crystalline. It was suggested that rapid heating under MWR results in random displacement of atoms, thus creating lattice strain . This decrystallization, or the formation of the amorphous phase, can also be thought of as a highly distorted lattice structure due to a high concentration of defects (vacancies and interstitials).…”

Section: Resultsmentioning

confidence: 99%

Defect‐Mediated Anisotropic Lattice Expansion in Ceramics as Evidence for Nonthermal Coupling between Electromagnetic Fields and Matter

et al. 2019

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Electromagnetic (EM) fields can trigger a range of surprising responses in materials. Microwave radiation (MWR), a type of EM field in the frequency range of 0.3–300 GHz, can lower the synthesis temperature required for ceramics such as TiO2 and induces mixed amorphous–crystalline phase compositions. To better understand the effects of MWR on matter, structural changes during microwave heating and MWR‐assisted synthesis using in situ synchrotron X‐ray diffraction are studied. Anisotropic expansion–contraction of lattice parameters under microwave‐radiation is observed, which contradicts the results from conventional thermal heating. When as‐received TiO2 powders are heated with MWR, an instantaneous decrease in the intensities of diffraction peaks indicates decrystallization/amorphization. High‐resolution electron microscopy supports these observations. Raman spectroscopy and X‐ray photoemission spectroscopy indicate increased defect‐generation under microwave exposure. Molecular dynamics simulations on the anatase phase of TiO2 suggests that introducing an oxygen vacancy can lead to the formation of an interstitial–vacancy pair resulting in anisotropic expansion–contraction of the lattice. These unique responses of ceramics under externally applied fields provide direct evidence for nonthermal coupling between EM fields and matter. Understanding such nonthermal, field‐driven processes has implications in engineering low‐temperature processes for integrating ceramics with polymers for flexible electronics, energy harnessing, and storage applications.

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Section: Resultsmentioning

confidence: 99%

Defect‐Mediated Anisotropic Lattice Expansion in Ceramics as Evidence for Nonthermal Coupling between Electromagnetic Fields and Matter

et al. 2019

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“…The PFT of S7 and S8 increased by 13.7% (S9) and 42% (S10) respectively after microwave processing (Figure 5c). The improved thermoelectric PFT of the microwave processed samples in comparison to SPS samples is also due to the non-linear transport of charge carriers between the decrystallized grains with compositional variation and/or disordered-crystalline regions [42,43,44].…”

Section: Resultsmentioning

confidence: 99%

N-Type Bismuth Telluride Nanocomposite Materials Optimization for Thermoelectric Generators in Wearable Applications

2019

Self Cite

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Thermoelectric materials could play a crucial role in the future of wearable electronic devices. They can continuously generate electricity from body heat. For efficient operation in wearable systems, in addition to a high thermoelectric figure of merit, zT, the thermoelectric material must have low thermal conductivity and a high Seebeck coefficient. In this study, we successfully synthesized high-performance nanocomposites of n-type Bi2Te2.7Se0.3, optimized especially for body heat harvesting and power generation applications. Different techniques such as dopant optimization, glass inclusion, microwave radiation in a single mode microwave cavity, and sintering conditions were used to optimize the temperature-dependent thermoelectric properties of Bi2Te2.7Se0.3. The effects of these techniques were studied and compared with each other. A room temperature thermal conductivity as low as 0.65 W/mK and high Seebeck coefficient of −297 μV/K were obtained for a wearable application, while maintaining a high thermoelectric figure of merit, zT, of 0.87 and an average zT of 0.82 over the entire temperature range of 25 °C to 225 °C, which makes the material appropriate for a variety of power generation applications.

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“…An example for the former is field-driven decrystallization of materials. 23,24,55,56 Bottom panel in Figure 3a shows an x-ray diffraction pattern, where the sharp peaks indicate crystalline anatase TiO 2 . 56 When exposed to time-varying microwave radiation at 2.45 GHz, peak intensity decreases drastically, indicating decrystallization.…”

Section: Fundamental Questions-atomistic Structural Changes Under Electric and Electromagnetic Fieldsmentioning

confidence: 99%

Far-from-equilibrium effects of electric and electromagnetic fields in ceramics synthesis and processing

Reeja‐Jayan

Luo

2021

MRS Bulletin

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Electric and electromagnetic fields can promote far-from-equilibrium chemical reactions, phase transformations, and microstructural evolution. On the one hand, both direct electric fields and time-varying electromagnetic fields can change the atomic and microscale structure of materials in ways that differ from conventional methods. On the other hand, ultrafast densification in a matter of seconds (e.g., in flash sintering) and electrically induced microstructural evolution open up new opportunities for materials processing. In many cases, the external fields absorbed within a material may result in "nonthermal" effects. In other cases, thermal effects dominate, but applied fields can still influence the microstructural evolution or generate nonequilibrium defects. Consequently, new behavior evolves such as ceramics that become ductile due to high densities of dislocations created by the far-from-equilibrium processing. Many open scientific questions remain about the fundamental mechanisms underlying such interactions of external fields with matter. From an industrial standpoint, processing advanced materials using externally applied fields can have a smaller energy footprint compared to conventional methods and as such will have a profound impact on society.

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Field induced decrystallization of silicon: Evidence of a microwave non-thermal effect

Cited by 29 publications

References 35 publications

Defect‐Mediated Anisotropic Lattice Expansion in Ceramics as Evidence for Nonthermal Coupling between Electromagnetic Fields and Matter

Defect‐Mediated Anisotropic Lattice Expansion in Ceramics as Evidence for Nonthermal Coupling between Electromagnetic Fields and Matter

N-Type Bismuth Telluride Nanocomposite Materials Optimization for Thermoelectric Generators in Wearable Applications

Far-from-equilibrium effects of electric and electromagnetic fields in ceramics synthesis and processing

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