A5049346955- Magnetic properties of thin films
- Magneto-Optical Properties and Applications
- Terahertz technology and applications
- Magnetic Properties and Applications
- Thermal Radiation and Cooling Technologies
- Advancements in Semiconductor Devices and Circuit Design
- Quantum and electron transport phenomena
- Photonic Crystals and Applications
- Metamaterials and Metasurfaces Applications
- Magnetic and transport properties of perovskites and related materials
- Characterization and Applications of Magnetic Nanoparticles
- Diamond and Carbon-based Materials Research
- Semiconductor materials and devices
- Graphene research and applications
- X-ray Spectroscopy and Fluorescence Analysis
- Advanced X-ray Imaging Techniques
- Crystallography and Radiation Phenomena
- Plasmonic and Surface Plasmon Research
- Molecular Junctions and Nanostructures
- Topological Materials and Phenomena
- Advanced Memory and Neural Computing
- Radiation Effects in Electronics
- Superconducting and THz Device Technology
- Electromagnetic Compatibility and Noise Suppression
- Advanced Materials and Mechanics
University of California, Berkeley
2021-2024
SRM Institute of Science and Technology
2022-2024
Lawrence Berkeley National Laboratory
2021-2023
Fraunhofer Institute for Photonic Microsystems
2022
Stockholm University
2018-2022
S.N. Bose National Centre for Basic Sciences
2011-2017
Material Sciences (United States)
2014
Abstract Silicon-based quantum emitters are candidates for large-scale qubit integration due to their single-photon emission properties and potential spin-photon interfaces with long spin coherence times. Here, we demonstrate local writing erasing of selected light-emitting defects using femtosecond laser pulses in combination hydrogen-based defect activation passivation at a single center level. By choosing forming gas (N 2 /H ) during thermal annealing carbon-implanted silicon, can select...
We investigate the shielding effectiveness and complex conductivity of single-walled carbon nanotubes (SWNT) distributed in a polyvinyl alcohol (PVA) matrix THz frequency range. SWNTs are dispersed PVA matrices with varying SWNT content (keeping thickness SWNT/PVA film constant) using slow-drying method, terahertz time-domain spectroscopy (THz-TDS) is performed at room temperature transmission geometry range 0.3-2.1 THz. The transmittance spectra show possible application composites as...
Abstract The discovery of ultrafast helicity‐independent all‐optical switching (HI‐AOS), as well picosecond all‐electrical a ferrimagnet, has inspired the spintronics community to explore ferromagnet achieve practical storage and memory devices. Two explored mechanisms HI‐AOS in ferromagnet‐ferrimagnet heterostructure are: a) exploiting indirect exchange coupling with b) injection non‐local spin current originated from ferrimagnet. In this manuscript, mediated Ruderman–Kittel–Kasuya–Yosida...
Electrically controllable nonvolatile magnetic memories show great potential for the replacement of conventional semiconductor-based memory technologies. Here, we experimentally demonstrate ultrafast spin-orbit torque (SOT)–induced coherent magnetization switching dynamics in a ferromagnet. We use an photoconducting switch and coplanar strip line to generate guide ~9-picosecond electrical pulse into heavy metal/ferromagnet multilayer induce SOT. then magneto-optical probing investigate with...
We report the polarizing behavior of aligned Ni nanoparticles (NPs) having average diameter 165±15 nm in ~210 μm thick polyvinyl alcohol (PVA) matrix frequency range 0.2-1.6 THz. The NPs have been prepared via a wet chemical route and then PVA film by using an external magnetic field. When polarization THz electric field is parallel to alignment direction, strong absorption observed whereas minimum noticed for corresponding perpendicular configuration. Degree calculated be 0.9±0.08....
We offer a perspective on the prospects of ultrafast spintronics and opto-magnetism as pathway to high-performance, energy-efficient, non-volatile embedded memory in digital integrated circuit applications. Conventional spintronic devices, such spin-transfer-torque magnetic-resistive random-access (STT-MRAM) spin–orbit torque MRAM, are promising due their non-volatility, energy-efficiency, high endurance. STT-MRAMs now entering into commercial market; however, they limited write speed...
Terahertz (THz) conductivity of single walled carbon nanotube (SWNT)/poly-vinyl alcohol (PVA) composites has been studied in the frequency window 0.3–2.0 THz. SWNT/PVA composite films with a constant thickness 300 ± 20 μm are grown by dispersing required amount SWNT PVA solution via slow drying process at room temperature under ambient condition. THz time domain spectroscopic measurements have performed transmission geometry N2 atmosphere and spectra extracted from data. It is found that...
In the present contribution we have experimentally demonstrated diameter dependence of terahertz (THz) shielding and THz conductivity multiwalled carbon nanotubes (MWNTs) performed detailed theoretical analysis to extract mechanism at different MWNT diameters. Self-standing films three types having same average length but outer tube (namely, MWNT_7, MWNT_25, MWNT_40 nm) are prepared by vacuum filtration technique. The effectiveness (SE) these in frequency range 0.4–2.2 is measured room...
The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, chemistry biology, giving researchers access X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided pulses at a relatively low repetition rate, limited data statistics. Here, results the first megahertz-repetition-rate scattering experiments Spectroscopy Coherent Scattering (SCS) instrument European...
We study THz-driven spin dynamics in thin CoPt films with perpendicular magnetic anisotropy. Femtosecond magneto-optical Kerr effect measurements show that demagnetization amplitude of about can be achieved a peak THz electric field 300 kV cm−1, and corresponding 0.1 T. The is more than an order magnitude larger observed samples easy-plane anisotropy irradiated the same strength. also utilize finite-element simulations to design meta-material structure enhance by magnitude, over area several...
A common technique for color center creation in wideband gap semiconductors employs ion implantation and a subsequent thermal annealing. In general, this annealing process is conducted an vacuum oven. Here, we exploit the based on femtosecond laser pulses. For that purpose, implant fluorine ions at 54 keV chlorine 74 diamond perform micrometer precise using focused pulses 800 ± (30) nm with different pulse numbers repetition rates. way, were able to create shallow spots centers of varying brightness.
Graphene nanoribbons (GNRs), when synthesized with atomic precision by bottom–up chemical approaches, possess tunable electronic structure, and high theoretical mobility, conductivity, heat dissipation capabilities, which makes them an excellent candidate for channel material in post-silicon transistors. Despite their immense potential, achieving highly transparent contacts efficient charge transport—which requires proper contact selection a deep understanding of the complex one-dimensional...
We use finite element simulations in both the frequency and time-domain to study terahertz resonance characteristics of a metamaterial (MM) comprising spiral connected straight arm. The MM acts as RLC circuit whose can be precisely tuned by varying characteristic geometrical parameters spiral: inner outer radius, width number turns. provide simple analytical model that uses these input give accurate estimates frequency. Finite show linearly polarized radiation efficiently couples thanks arm,...
We report the use of micrometer-sized copper (Cu) anti-dot structures as a novel terahertz (THz) anti-reflection coating (ARC) material and their superior performance over conventionally used metallic thin films. Cu two different thicknesses (7 10 nm) with varying diameters (100, 200, 300 μm, inter-anti-dot separation fixed at 100 μm) are deposited on silicon substrates by RF magnetron sputtering e-beam evaporation. The these samples is studied in frequency range 0.3-2.2 THz. While...
Atomically thin graphene layers can act as a spin-sink material when adjacent to nanoscale magnetic surface. The enhancement in the extrinsic spin–orbit coupling (SOC) strength of plays an important role absorbing spin angular momentum injected from surface after perturbation with external stimulus. As result, dynamics excited system is modified within layer. In this paper, we demonstrate modulation ultrafast magnetization at graphene/ferrimagnet interfaces using time-resolved...
We report the tunable conductivity of single walled carbon nanotubes and multi-walled with their surface walls decorated by Gold nanoparticles in elusive THz frequency range (0.3-2.0 THz). Colloidal gold were synthesized reduction chloride solution using tri-sodium citrate. A simple chemical route is followed to attach Au NP on surfaces nanotubes. spectra are explained help modified Universal Dielectric Response model.
Abstract We offer a brief overview of the present status ultrafast helicity-independent all-optical magnetization switching (HI-AOS) phenomena in ferromagnet (FM) films and multilayers. The discovery HI-AOS ferrimagnet alloys dates back to 2011. From an application standpoint, utilizing FM brings about several benefits. One these advantages is its enhanced spin polarization, which leads higher tunneling magneto-resistance (TMR) across magnetic tunnel junction device. TMR greatly enhances...
Here, we demonstrate local writing and erasing of selected light-emitting defects using fs laser pulses in combination with hydrogen-based defect activation passivation. By selecting forming gas (N2/H2) during thermal annealing carbon-implanted silicon, form Ci centers while passivating the more common G-centers. The center is a telecom S-band emitter very promising spin properties that consists single interstitial carbon atom silicon lattice. Density functional theory calculations show...