Finely Controlled Approaches to Formation of Heusler-Alloy/Semiconductor Heterostructures for Spintronics

Abstract

We present recent progress of the low-temperature growth of Heusler-alloy/silicon(Si) or Heusler-alloy/germanium(Ge) heterostructures and of their applications for spintronics. First, a concept of the realization of the low-temperature heteroepitaxy for high-quality Heusler alloy/ Si or Heusler alloy/Ge heterostructures is shown. Despite very low-growth temperatures, B2 or L2 1 ordered full-Heusler alloys are achieved. Next, by applying this concept to the growth of Ge on a Heusler alloy or a Heusler alloy on another Heusler alloy, we can also achieve unusual heterostructures for the possibility of novel spintronics applications. Finally, we demonstrate the pure spin current transport in Cu and Ge using these Heusler-alloy spin injectors and detectors. Our approaches will open new avenues for developing high-performance spintronic applications with Heusler alloys.

Growth of Fe3Si/Ge/Fe3Si trilayers on GaAs(001) using solid-phase epitaxy

“…13 FM/SC/FM hybrid trilayers could be grown with a variety of Heusler alloys in combination with Ge and Si in the (111) orientation using surfactant-mediated MBE 14 and low-temperature MBE. 11,32 However, the (001) orientation is preferable as it is more frequently used for semiconductor technology.…”

Great Differences between Low-Temperature Grown Co2FeSi and Co2MnSi Films on Single-Crystalline Oxides

“…Here we set the supplied atomic composition ratio of Co:Fe or Mn:Si to 2.0:1.0:1.0 during the growth. 55 Structural characterizations were investigated by using in situ RHEED observations, X-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy dispersive X-ray spectroscopy (EDX) measurements. Magnetic properties were measured by using a vibrating sample magnetometer in a physical property measurement system (Quantum Design).…”

“…Cooling the substrates down to <80 °C, we grew Co 2 FeSi and Co 2 MnSi films with a thickness of ∼25 nm by coevaporating Co, Fe, or Mn, and Si elements by using Knudsen cells, as schematically illustrated in Figure a. Here we set the supplied atomic composition ratio of Co:Fe or Mn:Si to 2.0:1.0:1.0 during the growth . Structural characterizations were investigated by using in situ RHEED observations, X-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy dispersive X-ray spectroscopy (EDX) measurements.…”

Spin transport in antimony-doped germanium detected using vertical spin-valve structures

“…Considering these facts, we utilize vertically stacked ferromagnet (FM)/Ge/FM spin-valve structures that we have already developed. 29,[37][38][39][40] Recently, since we already observed the spin-dependent transport through undoped p-Ge up to room temperature using an all-epitaxial CoFe/Ge/Fe 3 Si trilayer structure despite the very short spin diffusion length less than 100 nm, 29) the detection of the spin transport in Sb-doped Ge can be expected for the vertically stacked spin-valve structure.…”

“…45) Then, the Fe 3 Si surface was terminated with two monolayers of Si. 37,46,47) Subsequently, by combining solid phase epitaxy (SPE) and MBE with Sb doping, the Sbdoped Ge layer (∼150 nm) was grown on top of the Fe 3 Si layer. Detailed growth procedures have been published elsewhere.…”