Comparing amorphous silicon prepared by electron-beam evaporation and sputtering toward eliminating atomic tunneling states

JOURNAL OF ALLOYS AND COMPOUNDS

卷:855

Article

Liu, Xiao¹  Abernathy, Matthew R.^1,4  Metcalf, Thomas H.¹  Jugdersuren, Battogtokh²  Culbertson, James C.¹  Molina-Ruiz, Manel³  Hellman, Frances³ 

[1] Naval Res Lab, Code 7130, Washington, DC 20375 USA

[2] Jacobs Engn Grp, Hanover, MD 21076 USA

[3] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA

[4] Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA

关键词: Amorphous materials;    Thin films;    Reactive sputtering;    Quantum tunneling;    Acoustic properties;    Rutherford backscattering;   

DOI  :  10.1016/j.jallcom.2020.157431

来源: Elsevier

【 摘 要 】

It has previously been shown that amorphous silicon (a-Si) thin films can be produced free of tunneling two-level systems (TLS) by e-beam evaporation onto substrates held at elevated temperatures, and there appears to be a strong anticorrelation between the atomic density of these films and the number density of TLS. We have prepared a-Si films with higher atomic density using magnetron sputtering at substrate temperatures comparable to those used in the e-beam studies. We compare the atomic densities measured using Rutherford backscattering and the shear moduli, the speeds of sound, and the densities of TLS calculated using internal friction measurements at cryogenic temperatures of sputtered a-Si films to those of the e-beam films. Our results show that despite their higher atomic densities, sputtered a-Si films prepared at elevated substrate temperatures have lower speeds of sound and higher densities of TLS, which we attribute to the different film growth mechanism from that of e-beam evaporation. We conclude that a collaborative improvement of both local structure and network connectivity, determined by atomic density and speed of sound, respectively, to approach their crystalline values is required to eliminate atomic tunneling states. Published by Elsevier B.V.

【 授权许可】

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