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EuTiO3 (ETO) is a well-known complex oxide mainly investigated for its magnetic properties and its incipient ferro-electricity. In this work, we demonstrate the realization of suspended micro-mechanical structures, such as cantilevers and micro-bridges, from 100 nm-thick single-crystal epitaxial ETO films deposited on top of SrTiO3(100) substrates. By combining profile analysis and resonance frequency measurements of these devices, we obtain the Young’s modulus, strain, and strain gradients of the ETO thin films. Moreover, we investigate the ETO anti-ferro-distortive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. The comparison between experimental and literature data allows us to weight the contribution from thermal expansion and softening to the tuning slope, while a full understanding of the origin of such a wide hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.

Abstract The opto‐electronic properties of semiconducting 2D materials can be flexibly manipulated by engineering the atomic‐scale environment. This can be done by including 2D materials in tailored van der Waals (vdW) stacks, whose optical response is a function of the number and the type of adjacent 2D layers. This work reports a systematic investigation of the dielectric function of 2D semiconducting WS2 in various stacking configurations: monolayer, 3R/2H homobilayer, and WS2/MoS2 heterobilayer. Reliable, Kramers–Kronig‐consistent dielectric functions are obtained for WS2 in each configuration by means of spectroscopic ellipsometry (SE) and related parametric optical modeling in a wide spectral range (1.55–3.10 eV). The results of SE are combined with photoluminescence and absorbance spectra to identify the spectral position of the main excitonic features in WS2, which manifest sizable redshifts depending on the stacking configuration. These results represent a consistent reference set for the dielectric function of WS2 in vdW stacking configurations of particular interest for the scientific and technological field, and can be fruitfully exploited for reliable predictions of the optical response of WS2‐containing systems.

The combination of metallic nanostructures with two-dimensional transition metal dichalcogenides is an efficient way to make the optical properties of the latter more appealing for opto-electronic applications. In this work, we investigate the optical properties of monolayer WS2 flakes grown by chemical vapour deposition and transferred onto a densely-packed array of plasmonic Au nanoparticles (NPs). The optical response was measured as a function of the thickness of a dielectric spacer intercalated between the two materials and of the system temperature, in the 75–350 K range. We show that a weak interaction is established between WS2 and Au NPs, leading to temperature- and spacer-thickness-dependent coupling between the localized surface plasmon resonance of Au NPs and the WS2 exciton. We suggest that the closely-packed morphology of the plasmonic array promotes a high confinement of the electromagnetic field in regions inaccessible by the WS2 deposited on top. This allows the achievement of direct contact between WS2 and Au while preserving a strong connotation of the properties of the two materials also in the hybrid system.

In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS2 flakes were fabricated on SiO2/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes had a mean lateral size of 10–20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS2 flakes. Although the Fe coverage was much thicker than the MoS2 atomic step height (∼0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 were expected, a magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (Hc) was 28  ±  5 Oe, while in contrast, the Hc of 3.6 nm Fe/SiO2 ranged 58  ±  5 Oe. With a thicker Fe coverage of 7.0 nm, the Hc of Fe/MoS2 and Fe/SiO2 converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS2 for future spintronic applications. [ABSTRACT FROM AUTHOR]

We investigated the plasmonic response of arrays of Al nanowires fabricated in high-vacuum and embedded within a transparent protective medium. The nanostructures exhibited a strongly-birefringent plasmonic response which, depending on the mutual orientation of the incident-field polarization and the nanowire axis, allowed the plasmon resonance to span the whole spectral range from the visible to the deep-ultraviolet regime. Comparing the experimental data with theoretical calculations allowed to rationalize the optical response in terms of non-ideal nanowire morphologies arising from the bottom-up character of the nanofabrication method. The broadband plasmonic response suggests the potential application of these systems in plasmon-enhanced photovoltaics, exploiting the great advantage of the low-cost of aluminium. [ABSTRACT FROM AUTHOR]

We present a systematic investigation of the optical properties of cluster-assembled TiO2 films (20–150 nm nominal thickness) deposited onto Si wafers and processed with two types of ex-situ oxidation treatments. Spectroscopic ellipsometry (0.7–5 eV energy range), supported by x-ray photoelectron spectroscopy and atomic force microscopy measurements, allowed us to obtain information on the depth-dependent morphology of the films in a non-destructive mode. The characteristic grainy and porous structure of the films was modelled by means of a flexible effective-medium approach, allowing us to obtain a reliable estimate of the amount and distribution of voids into the films and their accessibility to foreign liquids. The absorption-edge broadening and significant optical absorptions within the gap were attributed to the intrinsically nanogranular morphology and to the interrelated defective structure/stoichiometry of the particles, also in relation to the occurrence of poorly accessible interstices or pores in the inner parts of the film. [ABSTRACT FROM AUTHOR]