Francesco Bisio

Superconducting and other Innovative Materials and Devices Institute

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M. Canepa

University of Genoa

L. Mattera

University of Genoa

R. Moroni

Superconducting and other Innovative Materials and Devices Institute

M. Magnozzi

University of Genoa

Camilla Coletti

Center for Nanotechnology Innovation

Marzia Ferrera

Italian Institute of Technology

J. Kirschner

Max Planck Institute of Microstructure Physics

Maria Sygletou

University of Genoa

Ornella Cavalleri

University of Genoa

F. Buatier de Mongeot

University of Genoa

Cooperative Institutions

University of Genoa

Italian Institute of Technology

Istituto Nazionale di Fisica Nucleare, Sezione di Genova

National Research Council

AREA Science Park

National Interuniversity Consortium for the Physical Sciences of Matter

Superconducting and other Innovative Materials and Devices Institute

Istituto Officina dei Materiali

Politecnico di Milano

Istituto Nazionale per la Fisica della Materia

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Integration of High‐Tc Superconductors with High‐Q‐Factor Oxide Mechanical Resonators

Advanced Functional Materials (2024)

Nicola Manca Alexei Kalaboukhov Alejandro Plaza L. Cichetto Eric Wahlberg

Abstract Micro‐mechanical resonators are building blocks of a variety of applications in basic science and consumer electronics. This device technology is mainly based on well‐established and reproducible silicon‐based fabrication processes with outstanding performances in term of mechanical Q ‐factor and sensitivity to external perturbations. Broadening the functionalities of micro‐electro‐mechanical systems (MEMS) by the integration of functional materials is a key step for both applied and fundamental science. However, combining functional materials with silicon‐based devices is challenging. An alternative approach is directly fabricating MEMS based on compounds inherently showing non‐trivial functional properties, such as transition metal oxides. Here, a full‐oxide approach is reported, where a high‐ superconductor YBa 2 Cu 3 O 7 (YBCO) is integrated with high Q ‐factor micro‐bridge resonators made of single‐crystal LaAlO 3 (LAO) thin films. LAO resonators are tensile strained, with a stress of about 350 MPa, show a Q ‐factor above 200k, and have low roughness. YBCO overlayers are grown ex situ by pulsed laser deposition and YBCO/LAO bridges show zero resistance below 78 K and mechanical properties similar to those of bare LAO resonators. These results open new possibilities toward the development of advanced transducers, such as bolometers or magnetic field detectors, as well as experiments in solid state physics, material science, and quantum opto‐mechanics.

10.1002/adfm.202403155

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Strain, Young's modulus, and structural transition of EuTiO3 thin films probed by micro-mechanical methods

arXiv (Cornell University) (2023)

Nicola Manca Gaia Tarsi Alexei Kalaboukhov Francesco Bisio Federico Caglieris

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-distorsive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. 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 the hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.

Hysteresis

10.48550/arxiv.2307.01022

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Optical Response of CVD-Grown ML-WS2 Flakes on an Ultra-Dense Au NP Plasmonic Array

Chemosensors (2022)

Marzia Ferrera Lorenzo Ramó Domenica Convertino G. Orlandini Simona Pace

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.

10.3390/chemosensors10030120

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Optical properties of cluster-assembled nanoporous gold films

Physical Review B (2009)

Francesco Bisio Marco Palombo Mirko Prato Ornella Cavalleri E. Barborini

We report a spectroscopic ellipsometry investigation of the electronic and morphological properties of cluster-assembled nanoporous metallic gold films deposited from a low-energy supersonic cluster beam. We modeled the optical response of the medium by explicitly introducing a variable degree of porosity in the film and finite-size effects due to the cluster nanometeric size. We deduced the characteristic size of the individual clusters within the nanoporous structure and their depth-resolved arrangement. Comparison with independent data available in the literature yielded extremely good quantitative agreement with the results extracted from our model, in terms of the degree of porosity of the films and of their surface roughness. The cluster-size distribution in the films obtained by the optical model matched extremely well the one obtained by atomic-force microscopy on isolated clusters. This demonstrates that, though the clusters are in contact with one another in the porous film, they retain their crystallographic individuality when assembled in three-dimensional structures.

Nanoporous

Ellipsometry

10.1103/physrevb.80.205428

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Citations (33)

Mechanisms of High-Order Perturbative Photoemission from Cu(001)

Physical Review Letters (2006)

Francesco Bisio M. Nývlt J. Franta Hrvoje Petek J. Kirschner

We observed high-order 2- to 4-photon photoemission and above threshold photoemission (ATP) processes with 3.07 eV light from the Cu(001) surface. The intensity of 3-photon photoemission via excitation through the $n=1$ image potential state significantly exceeded that of the 2-photon process. The ATP occurs either via single photon transitions from the image potential resonances above the vacuum level or by multiphoton transitions from image potential states below the vacuum level. The experimental ratio of the $m$- to $(m+1)$-photon process yields is sensitive to the electronic band structure of the solid.

10.1103/physrevlett.96.087601

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Citations (66)

Correlation between magnetism and structure in ultrathinFe∕Cu3Au(001)films

Physical Review B (2005)

Francesco Bisio S. Terreni M. Canepa L. Mattera

We have studied the correlation between the magnetic properties and the structure of ultrathin ferromagnetic $\mathrm{Fe}∕{\mathrm{Cu}}_{3}\mathrm{Au}(001)$ films for thicknesses up to 15 \AA{}. We have found that two different face centered tetragonal structural phases coexist within the film in the thickness range 5--15 \AA{}. The coexistence of the two structural phases induces an anomalous thickness dependence of the Curie temperature of the films. We ascribe this thickness dependence to a difference in the exchange coupling between the two phases. The irreversible modifications of the magnetic properties of the films after a mild thermal treatment are discussed on the basis of the corresponding changes of the structure and the morphology.

Tetragonal crystal system

Magnetism

10.1103/physrevb.72.174413

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Modulation of resistance switching in Au/Nb:SrTiO3 Schottky junctions by ambient oxygen

Applied Physics Letters (2012)

Renato Buzio Andrea Gerbi A. Gadaleta Luca Anghinolfi Francesco Bisio

We investigated the room-temperature current-voltage characteristics of Au/Nb:SrTiO3 Schottky junctions under various atmospheres and working pressures. We observed that oxygen partial pressure reversibly modulates junction response, briefly individual specimens behave as high-quality rectifiers in oxygen-rich atmospheres and as bipolar resistive switches in vacuum and inert gases. A two orders of magnitude modulation of resistance switching characterizes samples with the highest content of interfacial oxygen vacancies. We attribute this behavior to oxygen ionosorption and chemical oxidation at the metal-oxide interface. Our results are relevant to oxide devices displaying resistive switching at ambient-exposed interfaces, and might be exploited for gas detection purposes.

Inert gas

Resistive touchscreen

Modulation (music)

10.1063/1.4771603

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Citations (45)

Suppression of grain boundary contributions on carrier mobility in thin Al-doped ZnO epitaxial films

Applied Surface Science (2023)

Riccardo Magrin Maffei A. di Bona Maria Sygletou Francesco Bisio Sergio D’Addato

Realizing very thin transparent conductive (TCO) films is a key aspect of many applications, but often the film quality tends to worsen at very small thicknesses. In this work we demonstrate that Al-doped ZnO (AZO) thin films grown epitaxially on SrTiO3 retain their optimal properties even at thicknesses as low as 30 nm. We deposit by radio frequency magnetron sputtering and investigate the film morphology, structure, crystallinity, electrical and optical properties. We prove that the Hall mobility of epitaxial films is limited mostly by ionized impurity scattering, with a negligible contribution of grain boundary scattering, leading to comparably high mobility in thin epitaxial films. On the contrary, in polycrystalline films the properties of AZO films strongly deteriorate at reduced film thickness, due to grain boundary contributions. The optical carrier density and mobility do not change significantly between epitaxial and polycrystalline films, suggesting that the different electrical properties are indeed mainly due to grain boundary scattering and not to a reduction of carriers and intrinsic mobility. In this way we obtain an epitaxial thin TCO film with the optimal properties of a bulk by a scalable technique, paving the way to applications in plasmonic devices and in thin films solar cells.

Electron Mobility

10.1016/j.apsusc.2023.157133

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Polarization dependence and surface sensitivity of linear and nonlinear photoemission from Bi/Cu(111)

Physical Review B (2012)

A. A. Ünal Aimo Winkelmann Christian Tusche Francesco Bisio Martin Ellguth

We analyze the polarization dependence of photoelectron momentum maps observed in one-photon photoemission (1PPE) and two-photon photoemission (2PPE) from clean Cu(111) surfaces and from surface alloys of Bi on Cu(111). For clean Cu(111), we find similar emission patterns and a similar polarization dependence in 1PPE and 2PPE due to the dominating influence of direct optical transitions between initial and final bulk states. In contrast, on the Bi/Cu(111) surface, we observe significantly different emission patterns between linear and nonlinear photoemission measurements. This behavior is assigned to the presence of unoccupied states, which favor surface two-photon transitions specific to the Bi surface alloy and suppress the strong bulk contribution seen in 1PPE. The polarization dependence of the 2PPE momentum patterns can be assigned to the properties of the occupied states of the Bi/Cu(111) surface alloy, which we analyze with the help of one-step photoemission calculations.

Surface States

Inverse photoemission spectroscopy

10.1103/physrevb.86.125447

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Citations (10)

Plasmonic Color-Graded Nanosystems with Achromatic Subwavelength Architectures for Light Filtering and Advanced SERS Detection

ACS Applied Materials & Interfaces (2016)

Remo Proietti Zaccaria Francesco Bisio Gobind Das Giulia Maidecchi M. Caminale

Plasmonic color-graded systems are devices featuring a spatially variable plasmonic response over their surface. They are widely used as nanoscale color filters; their typical size is small enough to allow integration with miniaturized electronic circuits, paving the way to realize novel nanophotonic devices. Currently, most plasmonic color-graded systems are intrinsically discrete because their chromatic response exploits the tailored plasmon resonance of microarchitectures characterized by different size or geometry for each target color. Here, we report the realization of multifunctional plasmon-graded devices where continuously graded chromatic response is achieved by smoothly tuning the composition of the resonator material while simultaneously maintaining an achromatic nanoscale geometry. The result is a new class of versatile materials: we show their application as plasmonic filters with a potential pixel size smaller than half of the exciting wavelength but also as multiplexed surface-enhanced Raman spectroscopy (SERS) substrates. Many more implementations, such as photovoltaic efficiency boosters or color routers, await and will benefit from the low fabrication cost and intrinsic plasmonic flexibility of the presented systems.

Achromatic lens

Nanophotonics

Surface-Enhanced Raman Spectroscopy

10.1021/acsami.6b00726

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Citations (38)