arXiv subjects

Sara Gonzalez

Publications and source records attributed to Sara Gonzalez.

4 recordsLinked to original sources

arXiv2025

LIFY: IoT System for Monitoring Vital Signs of Elderly People

This article describes the implementation of a technological solution aimed at improving the recording of physiological signals in the elderly population residing in geriatric facilities. The developed system consists of a smart device equipped with sensors for body temperature, heart rate, and blood oxygen levels. This device establishes an Internet connection to transmit data to a cloud-based platform for storage. Within this platform, a dashboard has been created to visualize real-time values captured by the sensors, along with additional functionalities such as user management and the configuration of personalized alerts, which are transmitted to the solution's users through the instant messaging system called Telegram.

cs.NI↗

arXiv2025

Novel Electrical Characterization Method for Antiferroelectrics using a Positive Up Negative Down Approach

This study demonstrates the effectiveness of AFE-PUND, a revisited Positive Up Negative Down (PUND) protocol for characterizing antiferroelectric (AFE) materials, in analyzing $ZrO_2$ films across different thicknesses, revealing key trends. The proposed AFE-PUND method enables the isolation of switching currents from non-switching contributions, allowing precise extraction of remanent polarization and coercive field from hysteresis loops. The remanent polarization increases with film thickness, reflecting enhanced domain stability, while endurance cycles highlight the wake-up effect and its eventual degradation due to fatigue in thicker films. Similarly, coercive fields decrease with thickness, indicating reduced switching barriers and a clearer transition between tetragonal and orthorhombic phases. The method provides valuable insights into micro-structural influences, such as defect accumulation, grain size, and domain wall pinning, which critically affect device performance. AFE-PUND thus establishes itself as an essential tool for advancing the understanding and optimization of antiferroelectric materials.

cond-mat.mtrl-sci↗

arXiv2024

Comparative Performance of Fluorite-Structured Materials for Nanosupercapacitor Applications

Over the last fifteen years, ferroelectric and antiferroelectric ultra thin films based on fluorite-structured materials have drawn significant attention for a wide variety of applications requiring high integration density. Antiferroelectric $ZrO_2$, in particular, holds significant promise for nanosupercapacitors, owing to its potential for high energy storage density (ESD) and high efficiency ($η$). This work assesses the potential of high-performance $Hf_{1-x}Zr_{x}O_2$ thin films encapsulated by TiN electrodes that show linear dielectric (LD), ferroelectric (FE), and antiferroelectric (AFE) behavior. Oxides on silicon are grown by magnetron sputtering and plasma-enhanced atomic layer deposition. ESD and $η$ are compared for FE, AFE, and LD samples at the same electrical field (3.5 MV/cm). As expected, ESD is higher for the FE sample ($95 J/cm^3$), but $η$ is ridiculously small ($\approx$ 55%), because of the opening of the FE hysteresis curve inducing high loss. Conversely, LD samples exhibit the highest efficiency (nearly 100%), at the expense of a lower ESD. AFE $ZrO_2$ thin film strikes a balance between FE and LD behavior, showing reduced losses compared to the FE sample but an ESD as high as $52 J/cm^3$ at 3.5 MV/cm. This value can be further increased up to $84 J/cm^3$ at a higher electrical field (4.0 MV/cm), with an $η$ of 75%, among the highest values reported for fluorite-structured materials, offering promising perspectives for future optimization.

physics.app-ph↗

arXiv2020

Structural and electronic properties of the pure and stable elemental 3D topological Dirac semimetal $α$-Sn

In-plane compressively strained $α$-Sn films have been theoretically predicted and experimentally proven to possess non-trivial electronic states of a 3D topological Dirac semimetal. The robustness of these states typically strongly depends on purity, homogeneity and stability of the grown material itself. By developing a reliable fabrication process, we were able to grow pure strained $α$-Sn films on InSb(100), without heating of the substrate during growth, nor using any dopants. The $α$-Sn films were grown by molecular beam epitaxy, followed by experimental verification of the achieved chemical purity and structural properties of the film's surface. Local insight into the surface morphology was provided by scanning tunneling microscopy. We detected the existence of compressive strain using Mössbauer spectroscopy and we observed a remarkable robustness of the grown samples against ambient conditions. The topological character of the samples was confirmed by angle-resolved photoemission spectroscopy, revealing the Dirac cone of the topological surface state. Scanning tunneling spectroscopy, moreover, allowed obtaining an improved insight into the electronic structure of the 3D topological Dirac semimetal $α$-Sn above the Fermi level.

cond-mat.mtrl-sci↗