https://iopscience.iop.org/article/10.1088/2053-1583/aaf836/pdf

A roadmap for electronic grade 2D materials

Using angle-resolved photoemission spectroscopy, we report electronic structure for representative members of ternary topological insulators. We show that several members of this family, such as Bi2Se2Te, Bi2Te2Se, and GeBi2Te4, exhibit a singly degenerate Dirac-like surface state, while Bi2Se2S is a fully gapped insulator with no measurable surface state. One of these compounds, Bi2Se2Te, shows tunable surface state dispersion upon its electronic alloying with Sb (SbxBi2-xSe2Te series). Other members of the ternary family such as GeBi2Te4 and BiTe1.5S1.5 show an in-gap surface Dirac point, the former of which has been predicted to show nonzero weak topological invariants such as (1;111); thus belonging to a different topological class than BiTe1.5S1.5. The measured band structure presented here will be a valuable guide for interpreting transport, thermoelectric, and thermopower measurements on these compounds. The unique surface band topology observed in these compounds contributes towards identifying designer materials with desired flexibility needed for thermoelectric and spintronic device fabrication.

Topological surface states and Dirac point tuning in ternary topological insulators

One-dimensional growth mechanism of crystalline silicon nanowires

The emerging two-dimensional ferromagnetic materials present atomic layer thickness and a perfect interface feature, which have become an attractive research direction in the field of spintronics f...

Above Room-Temperature Ferromagnetism in Wafer-Scale Two-Dimensional van der Waals Fe3GeTe2 Tailored by a Topological Insulator.

We report the heteroepitaxy of single crystal thin films of Bi2Se3 on the (111)B surface of GaAs by molecular beam epitaxy. We find that Bi2Se3 grows highly c-axis oriented, with an atomically sharp interface with the GaAs substrate. By optimizing the growth of a very thin GaAs buffer layer before growing the Bi2Se3, we demonstrate the growth of thin films with atomically flat terraces over hundreds of nanometers. Initial time-resolved Kerr rotation measurements herald opportunities for probing coherent spin dynamics at the interface between a candidate topological insulator and a large class of GaAs-based heterostructures.

Coherent Heteroepitaxy of Bi2Se3 on GaAs (111)B

Visible photoluminescence (PL), optical transmission, and Raman scattering spectra of Si nanocrystals embedded in SiO2 matrix have been studied. Films were deposited by rf magnetron sputtering of compound SiO2/Si targets. Films containing silicon in the form of nanocrystals clusters show intense luminescence at room temperature. Films containing only amorphous Si clusters show little or no PL. Annealing in vacuum or in specific atmosphere leads to strong change of the PL spectrum and its intensity. Results are explained by strong influence of the Si/SiO2 interface state on integral PL emission.

Optical properties of Si nanocrystals prepared by magnetron sputtering

Growth of Bi2Te3 films and other phases of Bi-Te system by MOVPE

We present the generation and detection of spin currents by using magnetoelastic resonance excitation in a magnetoelectric composite high overtone bulk acoustic wave (BAW) resonator (HBAR) formed by a Al-ZnO-Al-GGG-YIG-Pt structure. Transversal BAW drives magnetization oscillations in YIG film at a given resonant magnetic field, and the resonant magneto-elastic coupling establishes the spin-current generation at the Pt/YIG interface. Due to the inverse spin Hall effect (ISHE) this BAW-driven spin current is converted to a dc voltage in the Pt layer. The dependence of the measured voltage both on magnetic field and frequency has a resonant character. The voltage is determined by the acoustic power in HBAR and changes its sign upon magnetic field reversal. We compare the experimentally observed amplitudes of the ISHE electrical field achieved by our method and other approaches to spin current generation that use surface acoustic waves and microwave resonators for ferromagnetic resonance excitation, with the theoretically expected values.

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Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

—In this paper, we present theoretical and experimental results on the excitation and detection of spin waves and spin currents in multifrequency bulk acoustic wave resonators containing iron–yttrium garnet (YIG) films in contact with the Pt film. Acoustically excited magnetic precession under the resonator conditions was established to produce spin pumping that also has a resonance character. A significant asymmetry in the frequency dependence of the voltage signal detected on the Pt film is revealed with respect to the frequency of the magnetoelastic resonance and is confirmed by theoretical calculations. Acoustic resonator spectroscopy in combination with the electric detection of magnetic dynamics using the inverse spin Hall effect is shown to be of interest for studying the dispersion of spin waves, as well as magnetic and magnetoelastic parameters of ferromagnetic films.

V. A. Luzanov

Papers

Optical properties of Si nanocrystals prepared by magnetron sputtering

Growth of Bi2Te3 films and other phases of Bi-Te system by MOVPE

Acoustic spin pumping in magnetoelectric bulk acoustic wave resonator

Electroacoustic Excitation of Spin Waves and Their Detection due to the Inverse Spin Hall Effect

Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3−xSex compounds