A5025322259- Pulsars and Gravitational Waves Research
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Cosmology and Gravitation Theories
- High-pressure geophysics and materials
- Thin-Film Transistor Technologies
- Atomic and Subatomic Physics Research
- Silicon Nanostructures and Photoluminescence
- Geophysics and Sensor Technology
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Theoretical and Computational Physics
- Material Dynamics and Properties
- Semiconductor materials and interfaces
- Silicon and Solar Cell Technologies
- Dark Matter and Cosmic Phenomena
- Metallic Glasses and Amorphous Alloys
- Glass properties and applications
- Seismic Waves and Analysis
- Magnetic properties of thin films
- Thermoelastic and Magnetoelastic Phenomena
- Force Microscopy Techniques and Applications
- Physics of Superconductivity and Magnetism
- Ion-surface interactions and analysis
University of California, Berkeley
2018-2024
University of California System
2024
Universitat Autònoma de Barcelona
2011-2015
Centre National de la Recherche Scientifique
2014
Institut Néel
2014
Université Grenoble Alpes
2014
A significant reduction in the N\'eel temperature of CoO ultrathin films is revealed by highly sensitive specific heat measurement. It found that consist weakly coupled antiferromagnetic (AF) grains. The ${T}_{N}$ from large to small grain samples scales with size reduction, according Binder theory critical phenomena systems reduced dimensions. In these finite AF nanosystems, intergrain exchange interaction presence surface Co spins, moments inside
In this paper, we demonstrate that in Ta/MgO/IrMn tunneling junctions, containing no ferromagnetic elements, distinct metastable resistance states can be set by field cooling the devices from above Néel temperature (TN) along different orientations. Variations of up to 10% are found upon applied fields, in-plane or out-of-plane. Well below TN, these insensitive magnetic fields 2 T, thus constituting robust memory states. Our work provides demonstration an electrically readable device, which...
The detection of gravitational waves from compact binary mergers by LIGO has opened the era wave astronomy, revealing a previously hidden side cosmos.To maximize reach existing observatory facilities, we have designed new instrument able to detect at distances 5 times further away than possible with Advanced LIGO, or greater 100 event rate.Observations this will make dramatic steps toward understanding physics nearby universe, as well observing universe out cosmological black hole...
We measure the thermal conductivity of a 17.5-nm-thick single crystalline Si layer by using suspended structure developed from silicon-on-insulator wafer, in which bridges platforms. The obtained value 19 Wm−1 K−1 at room temperature represents tenfold reduction with respect to bulk Si. This design paves way for subsequent lateral nanostructuration lithographic techniques, define different geometries such as nanowires, nanostrips or phononic grids. As proof concept, 0.5 × 10 μm have been...
The kinetics of intermediate phase formation between ultrathin films Pd (12 nm) and single-crystalline Si (100) is monitored by in-situ nanocalorimetry at ultrafast heating rates. heat capacity curves show an exothermic peak related to the Pd2Si. A kinetic model which goes beyond conventional linear-parabolic growth consider independent nucleation lateral Pd2Si along interface vertical mechanisms developed fit calorimetric curves. used extract effective interfacial nucleation/growth...
Kinetic processes involving intermediate phase formation are often assumed to follow an Arrhenius temperature dependence. This behavior is usually inferred from limited data over narrow intervals, where the exponential dependence generally fully satisfied. However, direct evidence wide intervals experimentally challenging and scarce. Here, we report a study of silicide between 12 nm film palladium 15 amorphous silicon in range heating rates, spanning six orders magnitude, 0.1 105 K/s, or...
We present a set-up designed for the measurement of specific heat very thin or ultra-thin quench condensed superconducting films. In an ultra-high vacuum chamber, materials interest can be thermally evaporated directly on silicon membrane regulated in temperature from 1.4 K to 10 K. On this membrane, heater and thermometer are lithographically fabricated, allowing capacity layers. This apparatus permits simultaneous thermal electrical characterization successively deposited layers situ...
The sensitivity of gravitational-wave detectors is limited by the mechanical loss associated with amorphous coatings detectors' mirrors. Amorphous silicon has higher refraction index and lower than current high-index coatings, but its optical absorption at wavelength used for present large. addition hydrogen to network reduces both films prepared under a range conditions all measured wavelengths temperatures, particularly large effect on grown room temperature. uptake greatest in...
The ability to observe astronomical events through the detection of gravitational waves relies on quality multilayer coatings used optical mirrors interferometers. Amorphous ${\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$ (including ${\mathrm{TiO}}_{2}:{\mathrm{Ta}}_{2}{\mathrm{O}}_{5}$) currently limits detector sensitivity due high mechanical loss. In this paper, loss measured at both cryogenic and room temperatures amorphous films grown by magnetron sputtering annealed in air 500...
Amorphous, ferrimagnetic Tb–Co thin films prepared with a Ta underlayer and either or Pt overlayer show evidence of both soft hard magnetic phases. At room temperature, the exhibit conventional ferromagnetism, but low temperature magnetometry measurements reveal decoupling two phases decreasing due to increased anisotropy energy layer at lower temperatures. Decreasing film thickness 2 nm, slightly above superparamagnetic limit found 1 soft, low-density phase was isolated be present in all as...
Thermoelastic loss is an important energy dissipation mechanisms in resonant systems. A careful analysis of the thermoelastic critical to design low-noise devices for high-precision applications, such as mirrors used gravitational-wave detectors. In this paper, we present analytical solutions due thermoelasticity between different materials that are contact. We find expressions multimaterial coatings finite substrates, and analyze its dependencies on material properties, mirror operating...
Abstract Specific heat measurements from 2 to 300 K of hydrogenated amorphous silicon prepared by hot-wire chemical vapor deposition show a large excess specific at low temperature, significantly larger than the Debye calculated measured sound velocity. The as-prepared films have Schottky anomaly that is associated with metastable hydrogen in network, as well linear and cubic term commonly tunneling two-level systems solids. Annealing 200 °C, temperature enables mobility but not evaporation,...
The use of a membrane-based chip nanocalorimeter in powder diffraction beamline is described. Simultaneous wide-angle X-ray scattering and scanning nanocalorimetric measurements are performed on thin-film stack palladium/amorphous silicon (Pd/a-Si) at heating rates from 0.1 to 10 K s(-1). works under power-compensation scheme previously developed by the authors. Kinetic structural information consumed created phases can be obtained combined techniques. formation Pd2Si produces broad...
Amorphous silicon contains tunneling two-level systems, which are the dominant energy loss mechanisms for amorphous solids at low temperatures. These systems affect both mechanical and electromagnetic oscillators believed to produce thermal noise loss. However, it is unclear whether that dominate dielectric losses same; former relies on phonon-TLS coupling, with an elastic field coupling constant, $\gamma$, while latter depends a TLS dipole moment, $p_0$, couples field. Mechanical...
Amorphous silicon films prepared by electron-beam evaporation have systematically and substantially greater atomic density for higher thickness, growth temperature, slower deposition rate, reaching the of crystalline Si when thickness than $\ensuremath{\sim}$300 nm are grown at 425 ${}^{\ensuremath{\circ}}$C $<$1 \AA{}/s. A combination spectroscopic techniques provide insight into disorder, local strains, dangling bonds, nanovoids. Electron diffraction shows that short-range order...
Specific heat measurements of hydrogenated amorphous silicon prepared by hot-wire chemical vapor deposition show a large density two-level systems at low temperature. Annealing 200 ${}^{\ensuremath{\circ}}\mathrm{C}$, well below the growth temperature, does not significantly affect already-low internal friction or sound velocity, but irreversibly reduces non-Debye specific an order magnitude 2 K, indicating reduction in systems. Comparison with suggests that are uncharacteristically...