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ACS Appl Mater Interfaces
ACS Appl Mater Interfaces
am
aamick
ACS Applied Materials & Interfaces
1944-8244
1944-8252
American Chemical Society

37327253
10.1021/acsami.3c05634
Research Article
B20 Weyl Semimetal CoSi Film Fabricated by Flash-Lamp Annealing
Li Zichao †§
Yuan Ye †‡
https://orcid.org/0000-0002-5200-6928
Hübner René †
Rebohle Lars †
https://orcid.org/0000-0001-5641-9191
Zhou Yan ∥
Helm Manfred †⊥
Nielsch Kornelius §⊥#
https://orcid.org/0000-0002-4088-6032
Prucnal Slawomir †
https://orcid.org/0000-0002-4885-799X
Zhou Shengqiang *†
† Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, 01328 Dresden, Germany
‡ Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People’s Republic of China
§ Institute of Materials Science, Technische Universität Dresden, 01069 Dresden, Germany
∥ School of Science and Engineering, Chinese University of Hong Kong, Shenzhen, Guangdong 518172, China
⊥ Institute of Applied Physics, Technische Universität Dresden, 01062 Dresden, Germany
# Institute for Metallic Materials, IFW Dresden, Dresden 01069, Germany
* Email: s.zhou@hzdr.de.
16 06 2023
28 06 2023
15 25 3051730523
20 04 2023
05 06 2023
© 2023 The Authors. Published by American Chemical Society
2023
The Authors
https://creativecommons.org/licenses/by/4.0/ Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/).

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.

Weyl semimetal
thin film
solid-phase epitaxy
CoSi
flash-lamp annealing
Deutsche Forschungsgemeinschaft 10.13039/501100001659 ZH 225/6-1 Basic and Applied Basic Research Foundation of Guangdong Province 10.13039/501100021171 2020A1515110891 China Scholarship Council 10.13039/501100004543 201707040077 document-id-old-9am3c05634
document-id-new-14am3c05634
ccc-price
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pmc1 Introduction

Cobalt monosilicide (CoSi) with a B20 crystal structure is a newly discovered Weyl semimetal due to the breaking of spatial inversion symmetry.1−3 In particular, B20-CoSi hosts two types of chiral topological fermions, a spin-1 chiral fermion and a double Weyl fermion in the center and corner of the Brillouin zone, respectively.4−6 Acting as a novel platform to study topological phenomena, bulk B20-CoSi was confirmed to exhibit very long Fermi arcs7,8 and chiral anomaly. The material was fabricated either by the chemical vapor transport method or by the floating zone method at high temperatures.9−11 One common feature in Co-Si compounds is that Co2Si or CoSi2 always coexists with B20-CoSi, and the Co-Si system with a ratio of Co and Si of around 1:1 is often used as a classical example to study eutectic growth.12−14 Co2Si is a strongly ferromagnetic material in thin films or nanoparticles, while it is a weakly magnetic material in the bulk form.15,16 CoSi2 has been reported to be a superconductor with a critical temperature of around 1.5 K and has been used as an ohmic contact material for Si microelectronics.17,18 In the phase diagram of the Co-Si system, Co2Si and CoSi2 are two close neighbors of the B20-CoSi phase: above around 1000 °C, the formation range of CoSi is broad, while it is very narrow in the low-temperature region. Therefore, most of the published papers are based on bulk CoSi grown at high temperatures.

It is known that thin films grown on substrates of technological relevance are appreciated for many practical applications.19−21 However, based on our current knowledge, there are only few studies about Weyl semimetal B20-CoSi films. In early reports about the growth of Co-silicide thin films, it was found that Co2Si and CoSi2 always coexist with B20-CoSi.22,23 Therefore, separating the Co-Si compounds is challenging but is necessary for understanding the topological properties of CoSi films. Tang et al. have first prepared polycrystalline CoSi films on Al2O3 by magnetron sputtering. They studied the spin Hall effect by using CoSi/CoFeB/MgO heterostructures.24 We have prepared single-phase B20-MnSi films by flash-lamp annealing thanks to their fast heating and cooling rates.25,26 By controlling the heating rates and the annealing temperature, different phases can be separated. Thus, this method probably offers a possibility to fabricate pure B20-CoSi films.

Here, we report the preparation of B20-CoSi films by flash-lamp annealing, which induces a fast reaction between the predeposited Co metal film and the Si substrate. By controlling the annealing temperature, B20-CoSi films without parasitic phases are successfully fabricated, as proven by X-ray diffraction, Raman scattering, and magnetization measurements. Transmission electron microscopy analysis also confirms the formation of stoichiometric B20-CoSi. Although the B20-CoSi film is polycrystalline, it shows signatures of the charge density wave and room-temperature chiral anomaly. Our preparation method can be a general phase-selective approach for the exploration of new Weyl semimetal films.

2 Experimental Section

2.1 Film Fabrication

In order to fabricate CoSi films, 25 nm Co films were first deposited on Si(100) wafers by DC magnetron sputtering. Then, the Co films were covered by 20 nm amorphous Si to avoid oxidation. Afterward, flash-lamp annealing (FLA) was employed to realize a fast solid-state reaction between Co and Si. During the FLA process, these samples were heated up by 12 Xe lamps in a continuous N2 flow.26 Samples were annealed from the rear side with different energy densities. With a 3 ms pulse duration, the heating and cooling rates were estimated to be in the magnitude of 105 and 102 ks–1, respectively. Such high heating/cooling rates will allow the control over the parasitic growth of Co2Si and CoSi2 in B20-type CoSi. By changing the flash-lamp energy (and therefore the peak temperature), we can selectively prepare films with the pure phases of CoSi and Co2Si or their mixture. More details about this method were reported in ref (26). The terms 3.8R, 4.0R, and 4.2R represent the samples annealed from the rear side by flash pulses of 3.8, 4.0, and 4.2 kV (the voltage applied to the capacitor of the flash lamps), corresponding to energy densities of 46, 50.5, and 55.5 J/cm2, respectively.

2.2 Structural Characterization

Grazing-incidence X-ray diffraction (GIXRD) was employed to analyze the crystalline phases in the obtained films. GIXRD was done on a Bruker D8 Advance diffractometer with a Cu-target source (Cu Kα, 40 keV, 40 mA) at a grazing incidence angle of 5°. Micro-Raman experiments were done using a Horiba micro-Raman system with an excitation wavelength of 532 nm and a spot size of around 1 μm, and the signal was recorded with a liquid-nitrogen-cooled silicon CCD camera. Cross-sectional bright-field and high-resolution TEM images were recorded with an image-Cs-corrected Titan 80–300 microscope (FEI) operated at an accelerating voltage of 300 kV. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and spectrum imaging analysis based on energy-dispersive X-ray spectroscopy (EDXS) were performed with a Talos F200X microscope (FEI) operated at 200 kV to obtain the elemental composition.

2.3 Magnetic and Electrical Properties

The magnetic properties of the films were measured by a superconducting quantum interference device equipped with a vibrating sample magnetometer (SQUID-VSM) with the field parallel (in-plane) to the films. The transport properties of the CoSi films were investigated by a Lake Shore Hall measurement system. Magnetic-field-dependent resistance was measured between 5 and 300 K using the van der Pauw (out-of-plane) or 4-point-probe (in-plane) geometry on samples with a size of around 5 × 5 mm2. Ag paste was used to contact the sample. The magnetic field was applied parallel to the sample surface plane (in-plane) or normal to the sample surface plane (out-of-plane). To observe the chiral anomaly, an in-plane magnetic field was applied parallel or vertical to the electrical field.

3 Results and Discussion

3.1 The Phase Formation and Microstructure

X-ray diffraction is a fast and nondestructive method that can be used to monitor the structural evolution of thin films depending on the preparation and annealing parameters.27Figure 1a displays the GIXRD patterns obtained from the samples prepared at different annealing parameters. For sample 3.8R (black, bottom curves) annealed at a low temperature, there is a broad Bragg peak present at around 45.3°, which may be from unreacted Co(111) or the newly formed Co2Si(013) or CoSi(210). The diffusion is limited by the low annealing temperature, which results in unreacted residual metallic Co and a low-temperature Co-rich phase, like Co2Si. Another peak at around 28.3° is from Si(111), which originates from the partially crystallized Si capping layer. Upon increasing the annealing energy to 50.5 J/cm2, the Bragg peak at 45.3° becomes narrower, and some new peaks appear, indicating the improvement of crystal quality and the formation of new phases. At this annealing energy, the peak at 28.3° becomes broader and shifts to a higher scattering angle of 28.4°, which is very probably the contribution of the new phase CoSi(110). Upon further increasing the annealing energy, the interdiffusion between Co and Si gets enhanced, and the Si capping layer also reacts with these diffused Co atoms. Sample 4.2R shows more pronounced diffraction peaks, which are consistent with B20-CoSi (PDF card no. 01-081-0484).28,29 Thus, by controlling the annealing temperature, we successfully prepared single-phase CoSi films.

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.

Raman spectroscopy is another useful technique for phase identification with a lateral resolution down to the (sub-)micrometer scale. To cross-check the phase formation of our samples 3.8R, 4.0R, and 4.2R, we measured 7 different positions for each sample. In general, different positions show similar results, proving the lateral homogeneity of our films. As shown in Figure 1b, the virgin sample has two broad peaks arising from the amorphous Si (a-Si) capping layer and one sharp peak at around 520.5 cm–1 caused by the transverse/longitudinal optical (TO/LO) phonon mode of the crystalline Si substrate (c-Si).30 For sample 3.8R, these two broad peaks get much weaker, indicating the beginning of the recrystallization of the amorphous Si capping layer. For sample 4.0R, one peak at around 150 cm–1 and another peak at around 200 cm–1 appear, corresponding to Co2Si and CoSi,31 respectively. It means that sample 4.0R contains two phases. With further increasing the annealing temperature, the Raman peak from Co2Si vanishes, and the CoSi peaks become stronger, indicating a pure CoSi phase in sample 4.2R. To confirm the preparation reproducibility, more samples are shown in the Supporting Information (Figures S1–S3).

As shown in Figure 1c, the Raman peak of B20-CoSi and Si for sample 4.2R can be detected from 4 to 300 K. With increasing the temperature, all Raman peaks for CoSi and Si shift to lower wavenumbers. The peak positions as a function of temperature are plotted in Figure 1d. The redshift with increasing temperature is well-understood as the thermal expansion. The tendency of the CoSi Raman shift is similar to Si, indicating that the thermal expansion is also the main reason for the redshift of the CoSi Raman peaks. It also indicates that there is no visible transition temperature from 4 to 300 K for CoSi films.

Figure 2a shows a representative cross-sectional bright-field TEM image of sample 4.2R. On top of the Si substrate (light-gray appearance with uniform brightness), there is an about 50 nm-thick film characterized by a sharp interface to the substrate. The varying contrast of this film points to its polycrystalline nature. A light-gray bead-like line, indicating the presence of a light element (see below), divides the upper third of this layer from the lower two-thirds. The top 15 nm-thick surface region has a structured appearance. To further characterize the phase structure of the continuous polycrystalline layer in the lower two-thirds, high-resolution TEM imaging (Figure 2b) combined with fast Fourier transform analysis (Figure 2c) was performed. Taking the B20-type CoSi structure, the diffractogram in Figure 2c can be described by a [11̅2] zone axis pattern. The spatially resolved distributions of the elements Co, Si, and O were characterized by EDXS-based analysis in the scanning TEM mode and are shown in Figure 2d. In particular, Co and Si are homogeneously distributed within the lower two-thirds of the silicide layer, and the Co:Si atomic ratio is determined to be 1:1 (Figure 2e). The bead-like layer is mainly depleted in cobalt and shows a significant O signal. The 15 nm-thick structured surface region is composed of Co silicide regions between oxidized silicon (Figure 2d,e). It should be mentioned that the weak oxygen signal within the Co silicide is caused by TEM lamella side-wall oxidation during storage in air. In summary, TEM analysis confirms the formation of a continuous polycrystalline B20-type CoSi film.

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).

3.2 Magnetic and Electrical Properties vs Annealing Parameters

The magnetic hysteresis (MH) curves measured at 5 K for all annealed samples are shown in Figure 3. The virgin sample has a strong saturation magnetization of around 1300 emu/cm3 and a small saturation field of around 100 Oe. The saturation magnetization is close to that of metallic Co.32 After annealing at an energy density of 46 J/cm2, the saturation magnetization decreases to 310 emu/cm3, and the saturation field increases to 1200 Oe. Though bulk Co2Si shows weak saturation magnetization, it is known that Co2Si thin films or nanowires show a strong ferromagnetic behavior.15,16 The saturation magnetization of sample 3.8R is close to the values in ref (16) (350 emu/cm3). With increasing the annealing energy to 50.5 J/cm2, most of the Co2Si grains transform into B20-CoSi, resulting in a dramatic decrease of the saturation magnetization to around 20 emu/cm3, since B20-CoSi is not ferromagnetic. Sample 4.2R with pure B20-CoSi has a negligible saturation magnetization, which is in good agreement with theory and experimental results for bulk CoSi.33 The zero-field cooling and field cooling magnetization measurements show consistent results regarding the phase transformation of all samples (see Figures S5 and S6 in the Supporting Information).

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 3b shows the temperature-dependent resistivity of all annealed films. The resistivity of sample 3.8R increases with increasing temperature, which is a typical metallic behavior.34 The resistivity of sample 4.0R also increases with temperature, indicating the mixed contribution of metallic Co2Si and semimetallic CoSi. With an increasing phase contribution of semimetallic CoSi, the resistivity increases. Sample 4.2R shows the highest resistivity and a clear deviation from metallic behavior, which will be discussed in detail in the next section. We also notice that at low temperatures, the residual resistivity in all samples is very high, leading to a low residual resistivity ratio. This is very probably due to the oxide impurities and the crystalline defects. Both can introduce additional scattering and increase the low-temperature resistivity. The out-of-plane magnetoresistance and the Hall resistance of the annealed samples are shown in Figure S7 in the supporting materials, which are totally different for the three samples composed of different Co silicide phases.

3.3 Magnetotransport Properties of the CoSi Film

Figure 4 shows the temperature-dependent resistivity (ρ) and the calculated derivative dρ/dT for sample 4.2R, which contains only B20-CoSi. Being much different from the metallic behavior, its resistivity does not show a monotonic dependence on temperature and is very close to the behavior of bulk CoSi.34 At around 40 K, we observe a change in the slope of the resistivity, which is more prominent in the derivative of the resistivity. The temperature coefficient of resistivity shows a broad peak at around 100 K, then decreases from 1.45 to 0.19 nΩ m K–1 at 40 K. Below 40 K, it starts to increase again up to 1.04 nΩ m K–1 at 12 K. This phenomenon is often attributed to the charge density wave (CDW) or spin density wave (SDW), but it is difficult to distinguish between CDW and SDW only by the resistivity.35,36 Comparing our magnetization results (Figure 3a) and the temperature-dependent magnetization (Figure S6) shown in the supporting materials, we assume that this resistance anomaly is very probably due to CDW.

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.

To check the chiral anomaly in the CoSi film, we investigated the magnetoresistance (MR), (RH is the resistance under magnetic fields, R0 is the resistance at zero field), for different field orientations. We applied the magnetic field (B) in-plane, being perpendicular (transverse magnetoresistance: TMR) or parallel (longitudinal magnetoresistance: LMR) to the electrical field (E) (schematics shown in Figure 5a). For many topological materials like Dirac or Weyl semimetals with chiral anomaly, negative LMR and positive TMR are observed.37−39 The chiral anomaly is a positive correction to the magnetoconductance when the magnetic field is parallel to the electrical (LMR) since the chiral symmetry of the Weyl fermions is broken. Thus, this effect does not appear when the magnetic field is perpendicular to the electrical field (TMR).34 Our results at high temperatures (200 and 300 K) shown in Figure 5e,f are in agreement with these observations. At lower temperatures (Figure 5b–d), LMR is also much bigger than TMR, indicating the influence of the chiral anomaly on our sample. At low temperatures, the magnetotransport is influenced by many other effects, like the weak antilocalization/weak localization and the appearance of CDW. In ref (34), the authors tried to decouple different effects in single-crystalline CoSi microribbons. For our thin films, a detailed analysis of the magnetotransport could be possible after properly optimizing the sample growth, i.e., by removing the top oxidized layer.

Figure 5 (a) Schematic for the parallel and perpendicular configuration of in-plane magnetoresistance. (b–f). LMR and TMR measurements at different temperatures.

4 Conclusions

In summary, in this work, we have succeeded in preparing B20-CoSi films on Si by nonequilibrium flash-lamp annealing. Comprehensive structural characterizations point to the importance of annealing energy density to eliminate the parasitic Co2Si phase. The magnetic and magnetotransport properties indicate the coexistence of the charge density wave and chiral anomaly in our CoSi films. For a better understanding of the CoSi films, it is required to optimize their preparation to obtain phase-pure, epitaxial films. The nonequilibrium solid-state reaction via millisecond-range flash-lamp annealing can be a versatile approach to prepare binary transition-metal silicides and germanides.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsami.3c05634.Additional measurements for the structural, magnetic, and magnetotransport properties (PDF)

Supplementary Material

am3c05634_si_001.pdf

The authors declare no competing financial interest.

Acknowledgments

The author Z.L. acknowledges the financial support from the China Scholarship Council (File No. 201707040077). The authors thank Romy Aniol for TEM specimen preparation and Andrea Scholz for XRD measurements. Furthermore, the use of the HZDR Ion Beam Center TEM facilities and the funding of TEM Talos by the German Federal Ministry of Education and Research (BMBF), Grant No. 03SF0451, in the framework of HEMCP are acknowledged. The work was also financially supported by the German Research Foundation (DFG, ZH 225/6-1) and by the Key Research and Development Program of Guangdong Province (Grant No. 2020B010174003). Y.Z. thanks the funding from the Guangdong Special Support Project (2019BT02X030), the Shenzhen Peacock Group Plan (KQTD20180413181702403), and the Shenzhen Fundamental Research Fund (Grant No. JCYJ20210324120213037).
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References

Tang P. ; Zhou Q. ; Zhang S. Multiple Types of Topological Fermions in Transition Metal Silicides. Phys. Rev. Lett. 2017, 119 , 206402 10.1103/PhysRevLett.119.206402.29219362
Rao Z. ; Li H. ; Zhang T. ; Tian S. ; Li C. ; Fu B. ; Tang C. ; Wang L. ; Li Z. ; Fan W. ; Li J. ; Huang Y. ; Liu Z. ; Long Y. ; Fang C. ; Weng H. ; Shi Y. ; Lei H. ; Sun Y. ; Qian T. ; Ding H. Observation of Unconventional Chiral Fermions with Long Fermi Arcs in CoSi. Nature 2019, 567 , 496–499. 10.1038/s41586-019-1031-8.30894751
Sanchez D. S. ; Belopolski I. ; Cochran T. A. ; Xu X. ; Yin J. ; Chang G. ; Xie W. ; Manna K. ; Süß V. ; Huang C. Y. ; Alidoust N. ; Multer D. ; Zhang S. S. ; Shumiya N. ; Wang X. ; Wang G. ; Chang T. R. ; Felser C. ; Xu S. Y. ; Jia S. ; Lin H. ; Hasan M. Z. Topological Chiral Crystals with Helicoid-arc Quantum States. Nature 2019, 567 , 500–505. 10.1038/s41586-019-1037-2.30894753
Takane D. ; Wang Z. ; Souma S. ; Nakayama K. ; Nakamura T. ; Oinuma H. ; Nakata Y. ; Iwasawa H. ; Cacho C. ; Kim T. ; Horiba K. ; Kumigashira H. ; Takahashi T. ; Ando Y. ; Sato T. Observation of chiral fermions with a large topological charge and associated Fermi-arc surface states in CoSi. Phys. Rev. Lett. 2019, 122 , 076402 10.1103/PhysRevLett.122.076402.30848650
Pshenay-Severin D. A. ; Ivanov Y. V. ; Burkov A. A. ; Burkov A. T. Band Structure and Unconventional Electronic Topology of CoSi. J. Phys.: Condens. Matter 2018, 30 , 135501 10.1088/1361-648X/aab0ba.29460854
Xu B. ; Fang Z. ; Sánchez-Martínez M. A. ; Venderbos J. W. F. ; Ni Z. ; Qiu T. ; Manna K. ; Wang K. ; Paglione J. ; Bernhard C. ; Felser C. ; Mele E. J. ; Grushin A. G. ; Rappe A. M. ; Wu L. Optical Signatures of Multifold Fermions in the Chiral Topological Semimetal CoSi. Proc. Natl. Acad. Sci. 2020, 117 , 27104–27110. 10.1073/pnas.2010752117.33077590
Yuan Q.-Q. ; Zhou L. ; Rao Z.-C. ; Tian S. ; Zhao W.-M. ; Xue C.-L. ; Liu Y. ; Zhang T. ; Tang C.-Y. ; Shi Z.-Q. ; Jia Z.-Y. ; Weng H. ; Ding H. ; Sun Y.-J. ; Lei H. ; Li S.-C. Quasiparticle Interference Evidence of the Topological Fermi Arc States in Chiral Fermionic Semimetal CoSi. Sci. Adv. 2019, 5 , eaaw9485 10.1126/sciadv.aaw9485.32064310
Ni Z. ; Wang K. ; Zhang Y. ; Pozo O. ; Xu B. ; Han X. ; Manna K. ; Paglione J. ; Felser C. ; Grushin A. G. ; de Juan F. ; Mele E. J. ; Wu L. Giant Topological Longitudinal Circular Photo-Galvanic Effect in the Chiral Multifold Semimetal CoSi. Nat. Commun. 2021, 12 , 6089 10.1038/s41467-020-20408-5.34667176
Xu X. ; Wang X. ; Cochran T. A. ; Sanchez D. S. ; Chang G. ; Belopolski I. ; Wang G. ; Liu Y. ; Tien H.-J. ; Gui X. ; Xie W. ; Hasan M. Z. ; Chang T.-R. ; Jia S. Crystal Growth and Quantum Oscillations in the Topological Chiral Semimetal CoSi. Phys. Rev. B 2019, 100 , 045104 10.1103/PhysRevB.100.045104.
Wu D. S. ; Mi Z. Y. ; Li Y. J. ; Wu W. ; Li P. L. ; Song Y. T. ; Liu G. T. ; Li G. ; Luo J. L. Single Crystal Growth and Magnetoresistivity of Topological Semimetal CoSi. Chin. Phys. Lett. 2019, 36 , 077102 10.1088/0256-307X/36/7/07710202.
Wang H. ; Xu S. ; Lu X.-Q. ; Wang X.-Y. ; Zeng X.-Y. ; Lin J.-F. ; Liu K. ; Lu Z.-Y. ; Xia T.-L. De Haas–van Alphen Quantum Oscillations and Electronic Structure in the Large-Chern-number Topological Chiral Semimetal CoSi. Phys. Rev. B 2020, 102 , 115129 10.1103/PhysRevB.102.115129.
Zhang L. ; Du Y. ; Ouyang Y. ; Xu H. ; Lu X. G. ; Liu Y. ; Kong Y. ; Wang J. Atomic Mobilities, Diffusivities and Simulation of Diffusion Growth in the Co–Si system. Acta Mater. 2008, 56 , 3940–3950. 10.1016/j.actamat.2008.04.017.
Zhang J. ; Wang H. ; Kuang W. ; Zhang Y. ; Li S. ; Zhao Y. ; Herlach D. M. Rapid Solidification of Nonstoichiometric Intermetallic Compounds: Modeling and Experimental Verification. Acta Mater. 2018, 148 , 86e99 10.1016/j.actamat.2018.01.040.
Jeon S. ; Kolbe M. ; Kaban V. ; String G. ; Cleaver A. ; Kaban I. ; Shuleshova O. ; Gao J. ; Matson D. M. Metastable Solidification Pathways of Undercooled Eutectic CoSi–CoSi2 Alloys. Acta Mater. 2019, 176 , 43–52. 10.1016/j.actamat.2019.06.048.
Seo K. ; Lee S. ; Yoon H. ; In J. ; Varadwaj K. S. K. ; Jo Y. ; Jung M.-H. ; Kim J. ; Kim B. Composition-tuned CoSi Nanowires: Location-selective Simultaneous Growth Along Temperature Gradient. ACS Nano 2009, 3 , 1145–1150. 10.1021/nn900191g.19388670
Balasubramanian B. ; George T. A. ; Manchanda P. ; Pahari R. ; Ullah A. ; Skomski P. ; Sellmyer D. J. Magnetic and Electron Transport Properties of Co2Si Nanomagnets. Phys. Rev. Mater. 2021, 5 , 024402 10.1103/PhysRevMaterials.5.024402.
Lenssen D. ; Mantl S. Observation of Quantum Interference Effects in Submicron CoSi2 Wires in Si(100). Appl. Phys. Lett. 1997, 71 , 3540 10.1063/1.120384.
Hsia S. L. ; Tan T. Y. ; Smith P. ; McGuire G. E. Resistance and Structural Stabilities of Epitaxial CoSi2 Films on (001) Si Substrates. J. Appl. Phys. 1992, 72 , 1864 10.1063/1.351659.
Xie Y. ; Yuan Y. ; Wang M. ; Xu C. ; Hübner R. ; Grenzer J. ; Zeng Y. J. ; Helm M. ; Zhou S. ; Prucnal S. Epitaxial Mn5Ge3 (100) layer on Ge (100) substrates obtained by flash lamp annealing. Appl. Phys. Lett. 2018, 113 , 222401 10.1063/1.5057733.
Li Y. ; Kanazawa N. ; Yu X. Z. ; Tsukazaki A. ; Kawasaki M. ; Ichikawa M. ; Jin X. F. ; Kagawa F. ; Tokura Y. Robust Formation of Skyrmions and Topological Hall Effect Anomaly in Epitaxial Thin Films of MnSi. Phys. Rev. Lett. 2013, 110 , 117202 10.1103/PhysRevLett.110.117202.25166569
Gajdzik M. ; Sürgers C. ; Kelemen M. ; Löhneysen H. Ferromagnetism in Carbon-Doped Mn5Si3 Films. J. Appl. Phys. 2000, 87 , 6013–6015. 10.1063/1.372597.
Aprilesi G. ; Mazzega E. ; Michelini M. ; Nava F. ; Queirolo G. ; Meda L. Electrical Transport Properties in Co-Silicides Formed by Thin Film Reactions. J. Appl. Phys. 1986, 60 , 310–317. 10.1063/1.337645.
Liu F. M. ; Ye J. H. ; Ren B. ; Yang Z. L. ; Liao Y. Y. ; See A. ; Chan L. ; Tian Z. Q. Raman Spectroscopic Studies of the Formation Processes of Cobalt Silicide Thin Films. Thin Solid Films 2005, 471 , 257 10.1016/j.tsf.2004.06.111.
Tang K. ; Lau Y.-C. ; Nawa K. ; Wen Z. ; Xiang Q. ; Sukegawa H. ; Seki T. ; Miura Y. ; Takanashi K. ; Mitani S. Spin Hall effect in a spin-1 chiral semimetal. Phys. Rev. Res. 2021, 3 , 033101 10.1103/PhysRevResearch.3.033101.
Li Z. ; Yuan Y. ; Hübner R. ; Begeza V. ; Naumann T. ; Rebohle L. ; Hellwig O. ; Helm M. ; Nielsch K. ; Prucnal S. ; Zhou S. B20-MnSi Films Grown on Si(100) Substrates with Magnetic Skyrmion Signature. Mater. Today Phys. 2021, 21 , 100541 10.1016/j.mtphys.2021.100541.
Li Z. ; Xie Y. ; Yuan Y. ; Ji Y. ; Begeza V. ; Cao L. ; Hübner R. ; Rebohle L. ; Helm M. ; Nielsch K. ; Prucnal S. ; Zhou S. Phase Selection in Mn-Si Alloys by Fast Solid-State Reaction with Enhanced Skyrmion Stability. Adv. Funct. Mater. 2021, 31 , 2009723 10.1002/adfm.202009723.
Zhou S. ; Potzger K. ; Reuther H. ; Talut G. ; Eichhorn F. ; von Borany J. ; Skorupa W. ; Helm M. ; Fassbender J. Crystallographically Oriented Magnetic ZnFe2O4 Nanoparticles Synthesized by Fe Implantation into ZnO. J. Phys. D: Appl. Phys. 2007, 40 , 964 10.1088/0022-3727/40/4/007.
Longhin M. ; Viennois R. ; Ravot D. ; Robin J. J. ; Papet P. Nanostructuration of CoSi by Mechanical Milling and Mechanical Alloying. Solid State Sci. 2014, 38 , 129 10.1016/j.solidstatesciences.2014.10.011.
Sun H. ; Lu X. ; Morelli D. T. Detrimental Effect of Powder Processing on the Thermoelectric Properties of CoSi. J. Mater. Sci. 2017, 52 , 8293–8299. 10.1007/s10853-017-1045-2.
Smith J. E. ; Brodsky M. H. ; Crowder B. L. ; Nathan M. I. ; Pinczuk A. Raman Spectra of Amorphous Si and Related Tetrahedrally Bonded Semiconductors. Phys. Rev. Lett. 1971, 26 , 642 10.1103/PhysRevLett.26.642.
Sedrati C. ; Bouabellou A. ; Kabir A. ; Haddad R. ; Boudissa M. ; Taabouche A. ; Fiad H. ; Hammoudi A. A Study of Nickel and Cobalt Silicides Formed in the Ni/Co/Si(100) System by Thermal Annealing. Mater. Sci.-Pol. 2020, 38 , 394–399. 10.2478/msp-2020-0057.
Bautin V. A. ; Seferyan A. G. ; Nesmeyanov M. S. ; Usov N. A. Magnetic Properties of Polycrystalline Cobalt Nanoparticles. AIP Adv. 2017, 7 , 045103 10.1063/1.4979889.
Stishov S. M. ; Petrova A. E. ; Sidorov V. A. ; Menzel D. Self-Doping Effects in Cobalt Silicide CoSi: Electrical, Magnetic, Elastic, and Thermodynamic Properties. Phys. Rev. B 2012, 86 , 064433 10.1103/PhysRevB.86.064433.
Schnatmann L. ; Geishendorf K. ; Lammel M. ; Damm C. ; Novikov S. ; Thomas A. ; Burkov A. ; Reith H. ; Nielsch K. ; Schierning G. Signatures of a Charge Density Wave Phase and the Chiral Anomaly in the Fermionic Material Cobalt Monosilicide CoSi. Adv. Electron. Mater. 2020, 6 , 1900857 10.1002/aelm.201900857.
Fukuyama H. ; Lee P. A. Dynamics of the Charge-Density Wave. I. Impurity Pinning in a Single Chain. Phys. Rev. B 1978, 17 , 535 10.1103/PhysRevB.17.535.
Fawcett E. ; Alberts H. L. ; Galkin V. Y. ; Noakes D. R. ; Yakhmi J. V. Spin-Density-Wave Antiferromagnetism in Chromium Alloys. Rev. Mod. Phys. 1994, 66 , 25 10.1103/RevModPhys.66.25.
Xiong J. ; Kushwaha S. K. ; Liang T. ; Krizan J. W. ; Hirschberger M. ; Wang W. ; Cava R. J. ; Ong N. P. Evidence for the Chiral Anomaly in the Dirac Semimetal Na3Bi. Science 2015, 350 , 413–416. 10.1126/science.aac6089.26338798
Huang X. ; Zhao L. ; Long Y. ; Wang P. ; Chen D. ; Yang Z. ; Liang H. ; Xue M. ; Weng H. ; Fang Z. ; Dai X. ; Chen G. Observation of the Chiral-Anomaly-Induced Negative Magnetoresistance in 3D Weyl Semimetal TaAs. Phys. Rev. X 2015, 5 , 031023 10.1103/PhysRevX.5.031023.
Zhang C.-L. ; Xu S.-Y. ; Belopolski I. ; Yuan Z. ; Lin Z. ; Tong B. ; Bian G. ; Alidoust N. ; Lee C.-C. ; Huang S.-M. ; Chang T.-R. ; Chang G. ; Hsu C.-H. ; Jeng H.-T. ; Neupane M. ; Sanchez D. S. ; Zheng H. ; Wang J. ; Lin H. ; Zhang C. ; Lu H.-Z. ; Shen S.-Q. ; Neupert T. ; Zahid Hasan M. ; Jia S. Signatures of the Adler–Bell–Jackiw Chiral Anomaly in a Weyl Fermion Semimetal. Nat. Commun. 2016, 7 , 10735 10.1038/ncomms10735.26911701