Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium-Nitride-based devices, specifically, AlGaN/GaN high-electron-mobility Transistors (HEMTs) with a novel packaging design provided by STMicroelectronics S.r.l. (Catania, Italy). The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of packaging.

For optical beams transmitted by a right-angle prism, the Goos–Hänchen shift can never be seen as a pure effect. Indeed, the lateral displacement, caused by the total internal reflection, will always be accompanied by angular deviations generated by the transmission through the incoming and outgoing interfaces. This combined effect can be analyzed by using the Taylor expansion of the Fresnel coefficients. The analytic expression found for the transmitted beam allows us to determine the beam parameters, the incidence angles, and the axial distance for which lateral displacements are compensated by angular deviations. Proposals to optimize experimental implementations are also briefly discussed.

Lattice defects, particularly oxygen vacancies, are commonly considered beneficial to photocatalytic performance, as they can reduce the bandgap, broaden the light absorption range, and suppress electron/hole recombination. In this perspective, high-entropy oxides (HEOs) could be considered “ideal” materials for photocatalysis because the random distribution of multiple metal cations within the crystalline lattice generates intrinsic structural disorder, which can be modulated by varying their composition and synthesis conditions. This work studies the photocatalytic activity of electrospun Cr–Mn–Fe–Co–Ni-based HEOs for the degradation of methylene blue in aqueous solution. The selected preparation conditions (calcination in air at 400 °C for 2 h) yield nanofibers consisting of ultra-small grains (≤9 nm) with copious oxygen vacancies on their surface. The presented results raise an important question: does the catalyst always promote the dye photodegradation or does it sometimes hinder it? A critical discussion is proposed, highlighting the case in which defects can induce competitive recombination pathways, negatively impacting the material’s photocatalytic performance.

Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium Nitride-based devices, specifically AlGaN/GaN High Electron Mobility Transistors (HEMTs) in a novel packaging design provided by STMicroelectronics S.r.l. The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of a packaging.

Archaeological research is increasingly relying on materials characterization protocols to provide information on artefacts and remains. Indeed, analytical results are fundamental to draw meaningful conclusions as concerns: raw materials procurement and provenance; technological advancement levels; commercial exchanges and societal aspects. Experimental measurements are done both ex-situ, by extracting small portions of material from the analyzed object, and in-situ, exploiting non-destructive techniques, that can probe the material without sampling or alteration. This approach is also interesting for ex-situ analyses, as it opens the possibility of combining different experimental techniques on the very same sample, even if a limited amount of material is available. In the present paper, we highlight the possibilities offered by the combined use of Raman and X-ray fluorescence (XRF) spectroscopy of Archaeological specimens. These two techniques are non-destructive and provide information on the elemental composition as well as on the structure of the investigated materials. The combined analytical and structural information is particularly important when dealing with natural materials, like garnets in the present study, commonly featuring intrinsic fluctuations in the chemical composition. Moreover, the approach can smoothly assess the actual origin of materials that can be of natural, like minerals, or anthropogenic, like glasses, origin. As a case study, we critically discuss the results obtained on two brooches, decorated with garnets and glasses, belonging to the Longobard culture in the North-Eastern Italian regions. The combination of the analytical data, from XRF spectroscopy, and of the structural ones, from Raman spectroscopy, provide indications on the composition of the base alloys and provenance of the mentioned stones.

The increasing demand for real-time monitoring systems has accelerated the adoption of distributed sensors operating in the ultra-low-power regime. However, in retrofittable and hard-to-access applications, providing a continuous external power supply is challenging, while batteries are limited by their lifetime and maintenance requirements. Energy harvesting represents a promising approach to enable autonomous sensor operation by exploiting ambient energy sources, including photovoltaic, thermal, mechanical, and electromagnetic sources. In this work, different circuit topologies for near-field electromagnetic energy harvesting are investigated through simulation and experimental validation. The proposed approach exploits the electromagnetic interference generated by shielded commercial power electronics, such as drivers and power supplies, as an available energy source. The results demonstrate the capability of compact and easily deployable circuits to capture and convert near-field electromagnetic energy into usable electrical power. The proposed methodology provides a flexible solution for powering low-power monitoring systems and can be adapted to different environments by tailoring the harvesting circuit parameters to the available electromagnetic source.