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Elena Blundo

Bio: Elena Blundo is an academic researcher from Sapienza University of Rome. The author has contributed to research in topics: Materials science & Medicine. The author has an hindex of 7, co-authored 16 publications receiving 186 citations.

Papers
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Journal ArticleDOI
23 Jan 2020
TL;DR: In this article, the effects of high strain on the optoelectronic properties of 2D crystals were investigated and the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers was demonstrated.
Abstract: This paper reports the effects of high strains on the optoelectronic properties of 2D crystals. By realizing micro- and nano-domes made of single layer transition-metal dichalcogenides, the authors demonstrate the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers. The indirect excitons can be harvested and potentially stored for long times, which is relevant for flexible photovoltaics devices and for inducing bosonic condensation.

94 citations

Journal ArticleDOI
TL;DR: Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications.
Abstract: At the few-atom-thick limit, transition-metal dichalcogenides (TMDs) exhibit strongly interconnected structural and optoelectronic properties. The possibility to tailor the latter by controlling the former is expected to have a great impact on applied and fundamental research. As shown here, proton irradiation deeply affects the surface morphology of bulk TMD crystals. Protons penetrate the top layer, resulting in the production and progressive accumulation of molecular hydrogen in the first interlayer region. This leads to the blistering of one-monolayer thick domes, which stud the crystal surface and locally turn the dark bulk material into an efficient light emitter. The domes are stable (>2-year lifetime) and robust, and host strong, complex strain fields. Lithographic techniques provide a means to engineer the formation process so that the domes can be produced with well-ordered positions and sizes tunable from the nanometer to the micrometer scale, with important prospects for so far unattainable applications.

60 citations

Journal ArticleDOI
TL;DR: Strain has been extensively studied in the literature for the purpose of tuning the properties of 2D materials and their properties on demand, among which the application of mechanical stresses, allowed by the incredible mechanical robustness and flexibility of these atomically thin materials, has been pursued as discussed by the authors.
Abstract: The variegated family of two-dimensional (2D) crystals has developed rapidly since the isolation of its forerunner: Graphene. Their plane-confined nature is typically associated with exceptional and peculiar electronic, optical, magnetic, and mechanical properties, heightening the interest of fundamental science and showing promise for applications. Methods for tuning their properties on demand have been pursued, among which the application of mechanical stresses, allowed by the incredible mechanical robustness and flexibility of these atomically thin materials. Great experimental and theoretical efforts have been focused on the development of straining protocols and on the evaluation of their impact on the peculiar properties of 2D crystals, revealing a novel, alluring physics. The relevance held by strain for 2D materials is introduced in Sec. I. Sections II and III present the multiplicity of methods developed to induce strain, highlighting the peculiarities, effectiveness, and drawbacks of each technique. Strain has largely widened the 2D material phase space in a quasi-seamless manner, leading to new and rich scenarios, which are discussed in Secs. IV–VI of this work. The effects of strain on the electronic, optical, vibrational, and mechanical properties of 2D crystals are discussed, as well as the possibility to exploit strain gradients for single-photon emission, non-linear optics, or valley/spintronics. Quantitative surveys of the relevant parameters governing these phenomena are provided. This review seeks to provide a comprehensive state-of-the-art overview of the straining methods and strain-induced effects, and to shed light on possible future paths. The aims and developments, the tools and strategies, and the achievements and challenges of this research field are widely presented and discussed.

59 citations

Journal ArticleDOI
TL;DR: In this article, a strain-induced direct-to-indirect band gap transition in mechanically deformed WS2 monolayers (MLs) is reported, where the necessary amount of strain is attained by proton irradiation of bulk WS2 and the ensuing formation of one-ML-thick, H2-filled domes.
Abstract: We report a strain-induced direct-to-indirect band gap transition in mechanically deformed WS2 monolayers (MLs). The necessary amount of strain is attained by proton irradiation of bulk WS2 and the ensuing formation of one-ML-thick, H2-filled domes. The electronic properties of the curved MLs are mapped by spatially- and time-resolved micro-photoluminescence revealing the mechanical stress conditions that trigger the variation of the band gap character. This general phenomenon, also observed in MoS2 and WSe2, further increases our understanding of the electronic structure of transition metal dichalcogenide MLs and holds a great relevance for their optoelectronic applications.

49 citations


Cited by
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Journal Article
TL;DR: In this article, the authors demonstrate first room temperature and ultrabright single photon emission from a color center in two-dimensional multilayer hexagonal boron nitride.
Abstract: We demonstrate first room temperature, and ultrabright single photon emission from a color center in two-dimensional multilayer hexagonal boron nitride. Density Functional Theory calculations indicate that vacancy-related centers are a likely source of the emission.

706 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed cutting-edge wearable power generation methodologies, for which they discuss their pros and cons, underlying physics, and general design/evaluation criteria.
Abstract: Wearable devices are drawing increasing attention in both academia and industry in that they can offer unprecedented information related to human health in real-time and human–machine interactions, which is expected to enable a paradigm shift in the digital world. For this shift to occur, green and sustainable energy technology for powering flexible wearable devices is a roadblock. This paper is dedicated to reviewing cutting-edge wearable power generation methodologies, for which we discuss their pros and cons, underlying physics, and general design/evaluation criteria. Sensor types, materials, processing technology, power consumption, and methods of testing the stretchability and flexibility of wearable devices are also summarized. Based on application scenarios in healthcare, industrial inspection, structural monitoring, armed forces and consumer electronics, an integrated system architecture of wearable, flexible systems is presented. Finally, future perspectives of wearable technologies are outlined by covering the aspects of all-in-one printable wearable electronics, fiber and textile electronics, self-powered self-awareness wearable systems, hybrid-integrated Systems on a Chip (SoC) for flexible electronics, and Internet of Things (IoT)-enabled self-contained systems towards full life cycle monitoring.

134 citations

Journal Article
TL;DR: In this paper, the stability of graphane was predicted based on first-principles total energy calculations, which is a fully saturated two-dimensional hydrocarbon derived from a single graphene sheet with formula CH.
Abstract: We predict the stability of an extended two-dimensional hydrocarbon on the basis of first-principles total-energy calculations. The compound that we call graphane is a fully saturated hydrocarbon derived from a single graphene sheet with formula CH. All of the carbon atoms are in $s{p}^{3}$ hybridization forming a hexagonal network and the hydrogen atoms are bonded to carbon on both sides of the plane in an alternating manner. Graphane is predicted to be stable with a binding energy comparable to other hydrocarbons such as benzene, cyclohexane, and polyethylene. We discuss possible routes for synthesizing graphane and potential applications as a hydrogen storage material and in two-dimensional electronics.

102 citations

Journal ArticleDOI
23 Jan 2020
TL;DR: In this article, the effects of high strain on the optoelectronic properties of 2D crystals were investigated and the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers was demonstrated.
Abstract: This paper reports the effects of high strains on the optoelectronic properties of 2D crystals. By realizing micro- and nano-domes made of single layer transition-metal dichalcogenides, the authors demonstrate the possibility to induce a clear-cut crossover from direct to indirect bandgap in strained monolayers. The indirect excitons can be harvested and potentially stored for long times, which is relevant for flexible photovoltaics devices and for inducing bosonic condensation.

94 citations

Journal ArticleDOI
TL;DR: In this article, the biaxial strain effects on the orbital, spin-orbit, and optical properties of monolayer transition-metal dichalcogenides (TMDCs) were analyzed using ab initio calculations.
Abstract: When considering transition-metal dichalcogenides (TMDCs) in van der Waals heterostructures for periodic ab initio calculations, usually, lattice mismatch is present, and the TMDC needs to be strained. In this study we provide a systematic assessment of biaxial strain effects on the orbital, spin-orbit, and optical properties of the monolayer TMDCs using ab initio calculations. We complement our analysis with a minimal tight-binding Hamiltonian that captures the low-energy bands of the TMDCs around the $K$ and ${K}^{\ensuremath{'}}$ valleys. We find characteristic trends of the orbital and spin-orbit parameters as a function of the biaxial strain. Specifically, the orbital gap decreases linearly, while the valence (conduction) band spin splitting increases (decreases) nonlinearly in magnitude when the lattice constant increases. Furthermore, employing the Bethe-Salpeter equation and the extracted parameters, we show the evolution of several exciton peaks, with biaxial strain, on different dielectric surroundings, which are particularly useful for interpreting experiments studying strain-tunable optical spectra of TMDCs.

90 citations