The efficiency of spin-to-charge conversion is a key parameter in determining the performance of emerging spintronic devices. In the topological surface state of a topological insulator (TI), the spin-momentum locking effect offers a great possibility for efficient spin-to-charge conversion. Here, we report the relation between the Fermi level position E F and spin-to-charge conversion efficiency in heterostructure Ni80Fe20 (Py)/(Bi1–x Sb x )2Te3. The band structure of (Bi1–x Sb x )2Te3 films becomes tailored by tuning the ratio of bismuth to antimony so that the position of the Fermi level E F varies from the top side of the valence band to the bottom side of the conduction band through the in-gap surface Dirac cone. The result is consistent with the electronic behavior of the majority carriers varying from n-type to p-type. In spin-pumping measurements, we observed that the inverse Edelstein effect length (λIEE) with a tuned E F near the Dirac point is significantly enhanced, indicating that the spin-charge conversion is determined mainly by the topological surface state. These results demonstrate that fine-tuning of E F in a TI-based heterostructure is critical to maximizing the efficiency of spin-to-charge conversion using a spin-momentum locking mechanism.

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The spin-to-charge conversion in Permalloy (Py)/Cu/Bi2Se3 is tunable by changing the Cu layer thickness. The conversion rate was studied using the spin pumping technique. The inverse Edelstein effect (IEE) length λIEE is found to increase up to ~2.7 nm when a 7 nm Cu layer is introduced. Interestingly, the maximized λIEE is obtained when the effective spin-mixing conductance (and thus Js) is decreased due to Cu insertion. The monotonic increase in λIEE with decreasing Js suggests that the IEE relaxation time (τ) is enhanced due to the additional tunnelling barrier (Cu layer) that limits the interfacial transmission rate. The results demonstrate the importance of interface engineering in the magnetic heterostructure of Py/topological insulators (TIs), the key factor in optimizing spin-to-charge conversion efficiency.

(Bi1−xSbx)2Se3 thin films were prepared by molecular beam epitaxy (MBE). The existence of strong and robust topological surface states was demonstrated in the (Bi1−xSbx)2Se3 ternary system by angle-resolved photoemission spectroscopy (ARPES). The sheet carrier density n2D was found to be decreased by 75% by doping Sb into Bi2Se3, compared with that in the case of undoped Bi2Se3. The enhancement of the surface state transport due to Sb doping was also revealed via the high-field Hall effect and weak antilocalization measurement. Our results reveal the potential of this system for the study of tunable topological-insulator based device physics.

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Phase‐change memory materials such as the pseudobinary GeTe‐Sb2Te3 compounds have recently gained attention for their good thermoelectric properties, which can be used for power‐generation/cooling applications. In this work, GeTe‐rich Ge–Sb–Te thin films deposited using a radio‐frequency magnetron sputtering method readily exhibit the metastable face‐centered cubic (FCC) phase at room temperature. This is in stark contrast to its bulk form, which only transforms to its FCC phase after a transition temperature of around 350 °C. Based on previous works, the FCC phase contributes to the superior thermoelectric properties of this material system. In this study, by decreasing the working deposition pressure, the preferred orientation of (200) plane is observed that translates to improved carrier mobility. Moreover, increasing the annealing temperature has been shown to decrease the carrier concentration due to Te deficiency, leading to a significant improvement in the Seebeck coefficient of the film. By combining these effects, an optimized thermoelectric power factor (21 μW/cm K2) was obtained at an operating temperature of 350 °C.

The current–voltage relations and magnetotransport properties of La0.7Sr0.3MnO3/Si-nanotips and La0.7Sr0.3MnO3/Si-film junctions are studied, revealing that their transport properties are dominated by various mechanisms depending on temperature and bias voltage. A giant positive magnetoresistance (PMR) of ∼200% is observed at 40 K in La0.7Sr0.3MnO3/Si-nanotips junction. The temperature dependence of resistance in the presence of magnetic field suggests the origin of giant PMR to be the strong electron–electron interaction and electron–magnon scattering. Interestingly, such behavior is not observed in regular La0.7Sr0.3MnO3/Si-film junction, implying that the coupling between spin and charge could be greatly enhanced at the interface of La0.7Sr0.3MnO3 and Si nanotips.

Patterned micropads made of metallic nanowires, 50 µm in diameter, are fabricated on a silicon substrate. An aluminium film patterned with SiO2 is anodized to fabricate a patterned nanoporous alumina (PNA) template in which metallic nanowires are electrodeposited. SiO2 that is deposited using the plasma-enhanced chemical vapour deposition process is demonstrated to be an effective barrier to anodization for the fabrication of high aspect ratio PNA templates. Current–voltage characteristics of an individual copper nanowire micropad display ohmic behaviour with a low resistance value of 5.5 mΩ. The nanowires are able to withstand the solder reflow process. Cu nanowire/Sn solder reflow reaction leads to Cu6Sn5 intermetallic formation. These micropads made of metallic nanowires have the potential for application as chip to substrate interconnects. Nanostructure synthesis is carried out using standard microelectronics fabrication techniques that would enable easy integration of such nanodevices into routine silicon manufacturing.