Effect of annealing on the structure and magnetic properties of Co2FeAl0.5Si0.5 thin films on Ge(111)

Kuerbanjiang, Balati; Love, Christopher; Kepaptsoglou, Demie; Nedelkoski, Zlatko; Yamada, Shinya; Ghasemi, Arsham; Ramasse, Quentin M.; Hamaya, Kohei; Cavill, S. A.; Lazarov, Vlado K.

doi:10.1016/j.jallcom.2018.03.075

Cited by 11 publications

(5 citation statements)

References 30 publications

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“…S1(a) in the Supplementary Material 36 ), as well as few atomic layers (∼3Å) of δ-doped P + Si insertion. The different crystallographic structure of Ge and CFAS shows the structural abruptness of the interface, and epitaxial relationship between the layers, previously stud-ied in details when CFAS is directly deposited on single crystal Ge(111) substrates 37,38 . We also note a presence of n + -Ge(111) atomic step terraces at the interface.…”

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confidence: 88%

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

et al. 2018

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We show a direct evidence for the impact of Heusler/semiconductor interfaces atomic structure on the spin transport signals in semiconductor-based lateral spin-valve (LSV) devices. Based on atomic scale Z contrast scanning transmission electron microscopy and energy dispersive x-ray spectroscopy we show that atomic order/disorder of Co2FeAl0.5Si0.5 (CFAS)/n-Ge LSV devices is critical for the spin injection in Ge. By conducting a post annealing of the LSV devices, we find 90% decrease in the spin signal while there is no difference in the electrical properties of the CFAS/n-Ge contacts and in the spin diffusion length of the n-Ge layer. We show that the reduction in the spin signals after annealing is attributed to the presence of intermixing phases at the Heusler/semiconductor interface. First principles calculations show how that intermixed interface region has drastically reduced spin polarisation at the Fermi level, which is the main cause for the significant decrease of the spin signal in the annealed devices above 300 • C.

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confidence: 88%

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

et al. 2018

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“…For anneal temperatures of 350 C, both CFAS/Si and CFAS/Ge show narrow and relatively sharp interface regions. As the anneal temperature is increased, the interfacial roughness increases accordingly due to mixing, 18 leading to a reduction in the amplitude of the Kiessig oscillations, especially at high angles (2h). The XRR results are consistent with previous electron based chemical mapping, showing that, above a critical anneal temperature, intermixing between the film and the substrate is ubiquitous.…”

Section: Articlementioning

confidence: 99%

“…The XRR results are consistent with previous electron based chemical mapping, showing that, above a critical anneal temperature, intermixing between the film and the substrate is ubiquitous. 18 Further details of the XRR analysis and crosssectional TEM, showing the effect of anneal temperature on the intermixing and size of the interface layer, can be found in the online supplementary material.…”

Section: Articlementioning

confidence: 99%

Substrate dependent reduction of Gilbert damping in annealed Heusler alloy thin films grown on group IV semiconductors

Love

Kuerbanjiang

Kerrigan

et al. 2021

Applied Physics Letters

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A structural and FMR study is presented for epitaxial thin films of the Heusler alloy Co 2 FeAl 0.5 Si 0.5 (CFAS) grown on Ge(111) and Si(111) substrates. All films, as-grown and post-annealed, show B2 ordering; full chemical order (L2 1 ) is not obtained over the range of anneal temperatures used in this study. As-grown films show a lower Gilbert damping constant, a, when grown on a Si(111) substrate compared to Ge(111). Annealing the films to 450 C significantly reduces a for CFAS on Ge while increasing a for CFAS on Si. This is related to a substrate dependent competition between improvements in lattice structure and increased interfacial intermixing as a function of anneal temperature. The optimal annealing temperature to minimize a is found to differ by $100 K between the two substrates. Above an anneal temperature of 500 C, films grown on both substrates have increased coercivity, decreased saturation magnetization, and show characteristic two-magnon scattering features.

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“…Thus, it is very important for the epitaxial growth of bcc FM alloys on Ge to use the atomic arrangement matching at the (1 1 1) plane between FM and Ge, as shown in figures 5(a) and (b). According to the postgrowth annealing experiments [104], the magnetic properties of CFAS/Ge(1 1 1) are stable up to 450 °C. The spin polarization of these bcc-alloys was roughly estimated from spin transport measurements in LSV devices with a Cu channel and transparent Heusler alloy/Cu interfaces [105][106][107][108].…”

Section: Epitaxially Grown Heusler Alloys As Spin Injector/detectormentioning

confidence: 99%

Spin transport and relaxation in germanium

Hamaya

Fujita

Yamada

et al. 2018

J. Phys. D: Appl. Phys.

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This paper reviews the recent progress in germanium (Ge) spintronics on the basis of the electrical spin injection from ferromagnets (FM), where Ge is a next generation semiconductor for applications such as CMOS and optical communication on the silicon platform. In general, four-terminal nonlocal voltage measurements in FM–Ge lateral spin-valve devices are important to discuss the spin transport and spin relaxation in n-Ge. First, to obtain relatively low contact resistance compared to the FM/MgO/Ge contacts, we introduce the formation of high-quality FM/Ge heterointerfaces with a phosphorus δ-doped Ge layer, where the atomic arrangement matching at the interface between the (1 1 1) surface of body-centered cubic FMs and Ge(1 1 1) is important. Next, we explain electrical detections of the spin transport in degenerate n-Ge. Owing to the Heusler alloy/Ge Schottky-tunnel barrier contacts, we obtain relatively large spin signals compared to those detected by using conventional CoFe contacts. Furthermore, we can experimentally determine the spin diffusion length and the spin lifetime in degenerate n-Ge by quantitatively analyzing the contact-distance dependence of the spin signals and the Hanle-effect curves. Since we can clarify the temperature dependence of the spin lifetime from 8 to 296 K, the spin relaxation mechanism in n-Ge can be understood as a consequence of the intervalley spin-flip scattering in the conduction band. We propose an advantage over GaAs systems by comparing the spin lifetimes between Ge and GaAs at around room temperature. Finally, we describe future prospects of Ge spintronics, including vertically fabricated device structures such as vertical spin MOSFETs and spin LEDs.

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Effect of annealing on the structure and magnetic properties of Co2FeAl0.5Si0.5 thin films on Ge(111)

Abstract: This is a repository copy of Effect of annealing on the structure and magnetic properties of Co2FeAl0.5Si0.5 thin films on Ge(111).

Cited by 11 publications

References 30 publications

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

Substrate dependent reduction of Gilbert damping in annealed Heusler alloy thin films grown on group IV semiconductors

Spin transport and relaxation in germanium

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