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. 2023 Jun 28;15(25):30517-30523.
doi: 10.1021/acsami.3c05634. Epub 2023 Jun 16.

B20 Weyl Semimetal CoSi Film Fabricated by Flash-Lamp Annealing

Zichao Li  1   2 , Ye Yuan  1   3 , René Hübner  1 , Lars Rebohle  1 , Yan Zhou  4 , Manfred Helm  1   5 , Kornelius Nielsch  2   5   6 , Slawomir Prucnal  1 , Shengqiang Zhou  1
Affiliations

B20 Weyl Semimetal CoSi Film Fabricated by Flash-Lamp Annealing

Zichao Li et al. ACS Appl Mater Interfaces. .

Abstract

B20-CoSi is a newly discovered Weyl semimetal that crystallizes into a noncentrosymmetric crystal structure. However, the investigation of B20-CoSi has so far been focused on bulk materials, whereas the growth of thin films on technology-relevant substrates is a prerequisite for most practical applications. In this study, we have used millisecond-range flash-lamp annealing, a nonequilibrium solid-state reaction, to grow B20-CoSi thin films. By optimizing the annealing parameters, we were able to obtain thin films with a pure B20-CoSi phase. The magnetic and transport measurements indicate the appearance of the charge density wave and chiral anomaly. Our work presents a promising method for preparing thin films of most binary B20 transition-metal silicides, which are candidates for topological Weyl semimetals.

Keywords: CoSi; Weyl semimetal; flash-lamp annealing; solid-phase epitaxy; thin film.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(a) GIXRD patterns and (b) Raman spectra of the annealed films on Si(100) by FLA. Sample 4.2R, annealed at the highest temperature, shows only the B20-CoSi phase. (c) Raman spectra of the annealed sample 4.2R measured at different temperatures. (d) Raman peak position as a function of the measurement temperature for CoSi (4.2R) and Si.
Figure 2
Figure 2
(a) Cross-sectional bright-field TEM image of the FLA-treated sample 4.2R. (b) High-resolution TEM image of the area marked with a dashed white square in panel (a). (c) Fast Fourier transform of the region marked with a white square in panel (b) and indexed based on a CoSi [11̅2] zone axis pattern. (d) Superimposed EDXS-based elemental distributions (blue: cobalt, green: silicon, and red: oxygen) for the area marked with a dashed white rectangle in panel (a), confirming the presence of a continuous B20-CoSi film. (e) Concentration–distance profile extracted from the line scan region indicated with a white arrow in panel (d).
Figure 3
Figure 3
(a) In-plane M–H curves measured at 5 K for the samples flash-annealed at various annealing parameters. The inset MH curves are for samples 4.0R and 4.2R. A further zoom-in for sample 4.2R is shown as Figure S4, in the Supporting Information. (b) Temperature-dependent resistivity of all annealed samples.
Figure 4
Figure 4
Temperature-dependent resistivity (ρ) and the calculated derivative dρ/dT for sample 4.2R. The shaded temperature range is the charge density wave zone.
Figure 5
Figure 5
(a) Schematic for the parallel and perpendicular configuration of in-plane magnetoresistance. (b–f). LMR and TMR measurements at different temperatures.
See this image and copyright information in PMC

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