arXiv subjects

Andrea Cattoni

Publications and source records attributed to Andrea Cattoni.

5 recordsLinked to original sources

arXiv2026

Integrated tunable magnonic devices for beyond 6 GHz signal processing

In the search for novel technology platforms supporting the transition towards ''beyond 6G'' telecommunications, magnonics is emerging as a viable route, primarily due to its intrinsic compatibility with the UWB-FR3 bands and its easy tunability. In this paper, we present a proof-of-concept device based on a CoFeB magnonic waveguide, fully integrated on silicon, which demonstrates all the key features of our integration approach, based on co-integrated hard magnetic micromagnets, magnonic conduits, reconfigurable soft magnetic elements and MEMS. The bias field enabling operation up to about 12 GHz is provided by SmCo micromagnets embedded in the silicon substrate. Real-time tunability is implemented in two ways. First, current-driven control is achieved via an integrated current line that generates an additional localized magnetic field, enabling continuous tuning of Backward Volume spin-wave propagation. Second, we achieve voltage-controlled tunability by integrating a NiFeMo soft magnetic element onto a piezoelectric MEMS cantilever and flip-chipping it onto the magnonic device. Upon actuation, the cantilever brings the NiFeMo into proximity with the permanent micromagnets, where it captures the stray field. The resulting voltage-controlled displacement modulates the coupling between the hard and soft magnetic components, effectively reducing the local bias field on the CoFeB waveguide and enabling fine control of Damon--Eshbach spin waves.

physics.app-ph↗

arXiv2025

Self Biased Integrated Magnonic Device

In the race towards "beyond 6G" telecommunication platforms, magnonics emerges as a promising solution due to its wide tunability within the FR3 band (7-24 GHz). So far, however, the need for an external magnetic bias field to allow the coherent excitation of spin waves has been a major bottleneck. Conventional bulky electromagnets are power-intensive and challenging to integrate on-chip, restricting magnonic applications largely to academic research. Here, we present the first demonstration of a standalone, tunable magnonic device featuring all-electric input and output, fully integrated on a silicon substrate with a compact footprint of 100 x 150 $\mu$m. The device consists of a CoFeB waveguide equipped with two radio frequency antennas, flanked by a symmetric configuration of T-shaped magnetic flux concentrators and rectangular SmCo permanent micromagnets. By varying the distance D between the flux concentrators and the permanent magnets from 0 to 12 $\mu$m, the transverse bias field can be tuned from 20.5 mT to 11 mT, respectively. This variation directly modulates the dispersion relation of Damon-Eshbach spin wave modes in the CoFeB waveguide. In these proof-of-concept devices, the spin wave frequency band ranges from 3 to 8 GHz, with precise phase shift tuning of up to 120 degrees at 6 GHz achieved by varying D within the 0-8 $\mu$m range. The operational frequency band could even be pushed to higher frequencies through optimized micromagnet engineering.

physics.app-ph↗

arXiv2024

Tuning magnonic devices with on-chip permanent micromagnets

One of the most appealing features of magnonics is the easy tunability of spin-waves propagation via external magnetic fields. Usually this requires bulky and power-hungry electromagnets which are not compatible with device miniaturization. Here we propose a different approach, exploiting the stray field from permanent micromagnets integrated on the same chip of a magnonic wave-guide. In our monolithic device, we employ two SmCo square micromagnets (10x10 $μ$m$^2$) flanking a CoFeB conduit at different distances from its axis, to produce a tunable transverse bias field between 7.5 and 3.0 mT in the conduit region between the magnets. Spin waves excited by an antenna just outside the region between the magnets enter a region with a variable higher (lower) effective field when an external bias field is applied parallel (antiparallel) to that from the micromagnets. Consequently, the attenuation length and phase shift of Damon-Eshbach spin waves can be tuned in a wide range by playing with the parallel-antiparallel configuration of the external bias and the distance between SmCo micromagnets and the CoFeB conduit. This work demonstrates the potential of permanent micro-magnets for the realization of low-power, integrated magnonic devices with tunable functionalities.

physics.app-ph↗

arXiv2022

Quantitative Assessment of Carrier Density by Cathodoluminescence. I. GaAs thin films and modeling

Doping is a fundamental property of semiconductors and constitutes the basis of modern microelectronic and optoelectronic devices. Their miniaturization requires contactless characterization of doping with nanometer scale resolution. Here, we use low- and room-temperature cathodoluminescence (CL) measurements to analyze p-type and n-type GaAs thin films over a wide range of carrier densities ($2\times 10^{17}$ to $1\times 10^{19}$ cm$^{-3}$). The spectral shift and broadening of CL spectra induced by shallow dopant states and band filling are the signature doping. We fit the whole spectral lineshapes with the generalized Planck's law and refined absorption models to extract the bandgap narrowing (BGN) and the band tail for both doping types, and the electron Fermi level for n doping. This work provides a rigorous method for the quantitative assessment of p-type and n-type carrier density using CL. Taking advantage of the high spatial resolution of CL, it can be used to map the doping in GaAs nanostructures, and it could be extended to other semiconductor materials.

cond-mat.mtrl-sci↗

arXiv2022

Quantitative Assessment of Carrier Density by Cathodoluminescence. II. GaAs nanowires

Precise control of doping in single nanowires (NWs) is essential for the development of NW-based devices. Here, we investigate a series of MBE-grown GaAs NWs with Be (p-type) and Si (n-type) doping using high-resolution cathodoluminescence (CL) mapping at low- and room-temperature. CL spectra are analyzed selectively in different regions of the NWs. Room-temperature luminescence is fitted with the generalized Planck law and an absorption model, and the bandgap and band tail width are extracted. For Be-doped GaAs NWs, the bandgap narrowing provides a quantitative determination of the hole concentration ranging from about $1\times 10^{18}$ to $2\times 10^{19}$~cm$^{-3}$, in good agreement with the targeted doping levels. High-resolution maps of the hole concentration demonstrate the homogeneous doping in the pure zinc-blende segment. For Si-doped GaAs NWs, the electron Fermi level and the full-width at half maximum of low-temperature CL spectra are used to assess the electron concentration to approximately $3\times 10^{17}$ to $6\times 10^{17}$~cm$^{-3}$. These findings confirm the difficulty to obtain highly-doped n-type GaAs NWs, maybe due to doping compensation. Notably, signatures of high concentration (5--9$\times 10^{18}$~cm$^{-3}$) at the very top of NWs are unveiled.

cond-mat.mtrl-sci↗