and duesberg@tcd.ie Platinum diselenide (PtSe 2 ) is a newly discovered 2D material which is of great interest for applications in electronics and catalysis. PtSe 2 films were synthesized by thermally-assisted selenization of predeposited platinum films and scanning transmission electron microscopy revealed the crystal structure of these films to be 1T. Raman scattering of these films was studied as a function of film thickness, laser wavelength and laser polarization. E g and A 1gRaman active modes were identified using polarization measurements in the Raman setup.These modes were found to display a clear position and intensity dependence with film thickness, for multiple excitation wavelengths, and their peak positions agree with simulated phonon dispersion curves for PtSe 2 . These results highlight the practicality of using Raman spectroscopy as a prime characterization technique for newly-synthesized 2D materials.
We report subnanometer modification enabled by an ultrafine helium ion beam. By adjusting ion dose and the beam profile, structural defects were controllably introduced in a few-layer molybdenum disulfide (MoS2) sample and its stoichiometry was modified by preferential sputtering of sulfur at a few-nanometer scale. Localized tuning of the resistivity of MoS2 was demonstrated and semiconducting, metallic-like, or insulating material was obtained by irradiation with different doses of He(+). Amorphous MoSx with metallic behavior has been demonstrated for the first time. Fabrication of MoS2 nanostructures with 7 nm dimensions and pristine crystal structure was also achieved. The damage at the edges of these nanostructures was typically confined to within 1 nm. Nanoribbons with widths as small as 1 nm were reproducibly fabricated. This nanoscale modification technique is a generalized approach that can be applied to various two-dimensional (2D) materials to produce a new range of 2D metamaterials.
We present magnetodielectric measurements in single crystals of the cubic spin-1/2 compound Cu2OSeO3. A magnetic field-induced electric polarization (P) and a finite magnetocapacitance (MC) is observed at the onset of the magnetically ordered state (Tc = 59 K). Both P and MC are explored in considerable detail as a function of temperature (T), applied field Ha, and relative field orientations with respect to the crystallographic axes. The magnetodielectric data show a number of anomalies which signal magnetic phase transitions, and allow to map out the phase diagram of the system in the Ha-T plane. Below the 3up-1down collinear ferrimagnetic phase, we find two additional magnetic phases. We demonstrate that these are related to the field-driven evolution of a long-period helical phase, which is stabilized by the chiral Dzyalozinskii-Moriya term D M·(∇×M) that is present in this non-centrosymmetric compound. We also present a phenomenological LandauGinzburg theory for the MEH effect, which is in excellent agreement with experimental data, and shows three novel features: (i) the polarization P has a uniform as well as a long-wavelength spatial component that is given by the pitch of the magnetic helices, (ii) the uniform component of P points along the vector (, and (iii) its strength is proportional to η 2 − η 2 ⊥ /2, where η is the longitudinal and η ⊥ is the transverse (and spiraling) component of the magnetic ordering. Hence, the field dependence of P provides a clear signature of the evolution of a conical helix under a magnetic field. A similar phenomenological theory is discussed for the MC.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.