Self-Diffusion in Amorphous Silicon

Strauß, Florian; Dörrer, Lars; Geue, Thomas; Stahn, J.; Koutsioubas, Alexandros; Mattauch, Stefan; Schmidt, Harald

doi:10.1103/physrevlett.116.025901

Cited by 26 publications

(39 citation statements)

References 56 publications

(69 reference statements)

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“…Also prolonged annealing of a sample up to 109 h at 500 C does not lead to a further significant intensity decrease. Annealing at temperatures of 550 C and above, where long range diffusion is present, 25,26 clearly shows that a further reduction of the Bragg peak to values lower than 70% of the initial value can be observed. This demonstrates that diffusion is frozen-in for long annealing times at the given temperature and atomic motion is restricted to short annealing times and consequently to short range distances of 1 to 3 nm (as will be shown later).…”

Section: Resultsmentioning

confidence: 97%

“…25 All samples discussed in this study are X-ray amorphous as proven by grazing incidence diffractometry (GI-XRD), using a Bruker D 5000 machine. 25,26 The isotope modulation of the samples in the direction perpendicular to the surface was verified by Secondary Ion Mass Spectrometry (SIMS). Due to the difference in neutron scattering lengths of 29 Si (4.70 fm) and nat Si (4.15 fm) this system is well-suited for neutron scattering.…”

Section: Methodsmentioning

confidence: 99%

“…Although silicon single crystals are one of the best characterized types of materials, also concerning their diffusion properties, 23,24 there actually exist no reliable experimental data on self-diffusivities in a-Si except our own previous work. 25,26 This fact results from the combination of the intrinsic structural metastability of a-Si in combination with the expected low diffusivities due to covalent bonding. Recently, we published results on self-diffusion in amorphous silicon thin films in the temperature range between 550 and 700 C. The diffusivities obey the Arrhenius law with an activation enthalpy of 4.4 eV, which is only 0.55 eV lower than that found for crystalline silicon at temperatures above 900 C. 26 The activation enthalpy is assumed to be composed of a formation and a migration part of (essentially unknown) defects that govern diffusion.…”

Section: Introductionmentioning

confidence: 99%

“…25,26 This fact results from the combination of the intrinsic structural metastability of a-Si in combination with the expected low diffusivities due to covalent bonding. Recently, we published results on self-diffusion in amorphous silicon thin films in the temperature range between 550 and 700 C. The diffusivities obey the Arrhenius law with an activation enthalpy of 4.4 eV, which is only 0.55 eV lower than that found for crystalline silicon at temperatures above 900 C. 26 The activation enthalpy is assumed to be composed of a formation and a migration part of (essentially unknown) defects that govern diffusion. 26 No time dependence of diffusivities could be proven in the investigated time-temperature domain above 500 C. 25,26 At about 700 C the diffusivities of a-Si are about five orders of magnitude higher than that in crystalline silicon (c-Si), which is traced back to an anomalous high pre-exponential factor and hence diffusion entropy.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Short range atomic migration in amorphous silicon

Strauß

Jerliu

Geue

et al. 2016

Journal of Applied Physics

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Experiments on self-diffusion in amorphous silicon between 400 and 500 C are presented, which were carried out by neutron reflectometry in combination with 29 Si/ nat Si isotope multilayers. Short range diffusion is detected on a length scale of about 2 nm, while long range diffusion is absent. Diffusivities are in the order of 10 À19-10 À20 m 2 /s and decrease with increasing annealing time, reaching an undetectable low value for long annealing times. This behavior is strongly correlated to structural relaxation and can be explained as a result of point defect annihilation. Diffusivities for short annealing times of 60 s follow the Arrhenius law with an activation enthalpy of (0.74 6 0.21) eV, which is interpreted as the activation enthalpy of Si migration. Published by AIP Publishing.

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Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Short range atomic migration in amorphous silicon

Strauß

Jerliu

Geue

et al. 2016

Journal of Applied Physics

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“…Our study employs a unique oxygen-isotope ZnO heterostructures with delicately-controlled chemical potential () and Fermi level (EF). Unlike the gaseous-exchange technique, which has absorption and evaporation problems 23,24 , the self-diffusion in the isotope heterostructures provides reliable information on the energetics and electronic properties of point defects [25][26][27] . We A show unambiguously that the diffusion process of oxygen atoms in ZnO is predominantly mediated by VO rather than oxygen interstitial (Oi).…”

mentioning

confidence: 99%

Oxygen vacancies: The origin ofn-type conductivity in ZnO

et al. 2016

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Oxygen vacancy (VO) is a common native point defects that plays crucial roles in determining the physical and chemical properties of metal oxides such as ZnO. However, fundamental understanding of VO is still very sparse. Specifically, whether VO is mainly responsible for the n-type conductivity in ZnO has been still unsettled in the past fifty years. Here we report on a study of oxygen self-diffusion by conceiving and growing oxygen-isotope ZnO heterostructures with delicately-controlled chemical potential and Fermi level. The diffusion process is found to be predominantly mediated by VO. We further demonstrate that, in contrast to the general belief of their neutral attribute, the oxygen vacancies in ZnO are actually +2 charged and thus responsible for the unintentional n-type conductivity as well as the non-stoichiometry of ZnO. The methodology can be extended to study oxygen-related point defects and their energetics in other technologically important oxide materials.

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A free energy landscape perspective on the nature of collective diffusion in amorphous solids

Wang

Shinzato

et al. 2018

Acta Materialia

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The nature of collective diffusion in amorphous solids is in strong contrast with diffusion in crystals. However, the atomic-scale mechanism and kinetics of such collective diffusion remains elusive. Here the free energy landscape of collective diffusion triggered by single atom hopping in a prototypical Cu 50 Zr 50 metallic glass is explored with well-tempered metadynamics which significantly expands the observation timescale of diffusion at atomic-scale. We clarify an experimentally suggested collective atomic diffusion mechanism in the deep glassy state. The collective nature is strongly temperature-dependent. It evolves from string-like motion with only several atoms to be large size collective diffusion at high temperature, which can promote the atomic transport upon glass transition temperature. We also clarify the apparent diffusivity is dominated by the highest free energy barrier of atomic diffusion among widely distributed free energy barriers due to the dynamic heterogeneity of metallic glass, which suggests the sequential nature of diffusion is a proper assumption to the metallic glasses with dynamic heterogeneity. The temperature and pressure dependence of diffusion free energy landscape are further quantified with activation entropy, (19.6 ± 2.5)k B , and activation volume, (7.9 ± 3.4) Å 3 , which agree quantitatively with experiments. Laboratory timescale simulations of atomic diffusion brings physical insights into the unique atomic motion mechanism in non-crystalline materials.

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Self-Diffusion in Amorphous Silicon

Cited by 26 publications

References 56 publications

Short range atomic migration in amorphous silicon

Short range atomic migration in amorphous silicon

Oxygen vacancies: The origin ofn-type conductivity in ZnO

A free energy landscape perspective on the nature of collective diffusion in amorphous solids

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