A5079808043- Graphene research and applications
- Thermal properties of materials
- 2D Materials and Applications
- Thermal Radiation and Cooling Technologies
- Quantum and electron transport phenomena
- Organic and Molecular Conductors Research
- Perovskite Materials and Applications
- Electromagnetic wave absorption materials
- Physics of Superconductivity and Magnetism
- Diamond and Carbon-based Materials Research
- MXene and MAX Phase Materials
- Advanced Antenna and Metasurface Technologies
- Carbon Nanotubes in Composites
- Topological Materials and Phenomena
- Transition Metal Oxide Nanomaterials
- Magnetic properties of thin films
- Mechanical and Optical Resonators
- GaN-based semiconductor devices and materials
- Molecular Junctions and Nanostructures
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- ZnO doping and properties
- High-pressure geophysics and materials
- Advanced Thermoelectric Materials and Devices
- Acoustic Wave Resonator Technologies
University of California, Riverside
2015-2024
Auburn University
2024
University of California, Los Angeles
2023-2024
California NanoSystems Institute
2024
SCI Engineered Materials (United States)
2021
Materials Science & Engineering
2019-2021
University at Buffalo, State University of New York
2021
University of California System
2019
Riverside
2019
Universidade Federal do Rio de Janeiro
2017
We investigated thermal properties of the epoxy-based composites with high loading fraction-up to f ≈ 45 vol %-of randomly oriented electrically conductive graphene fillers and insulating boron nitride fillers. It was found that both types revealed a distinctive percolation threshold at fraction fT > 20 %. The required for achieving percolation, fT, substantially higher than loading, fE, electrical percolation. Graphene outperformed in conductivity enhancement. established transport filler...
Abstract The thermal properties of epoxy‐based binary composites comprised graphene and copper nanoparticles are reported. It is found that the “synergistic” filler effect, revealed as a strong enhancement conductivity with size‐dissimilar fillers, has well‐defined loading threshold. moderate concentration f g = 15 wt% exhibits an abrupt increase approaches Cu ≈ 40 wt%, followed by saturation. effect attributed to intercalation spherical between large flakes, resulting in formation highly...
Abstract The synthesis and characterization of epoxy‐based composites with few‐layer graphene fillers, which are capable dual‐functional applications, reported. It is found that certain types fillers reveal an efficient total electromagnetic interference shielding, SE tot ≈ 45 dB, in the important X‐band frequency range, f = 8.2 −12.4 GHz, while simultaneously providing high thermal conductivity, K 8 W m −1 , a factor ×35 larger than base matrix material. efficiency application depends on...
Nickel oxide (NiO) has been studied extensively for various applications ranging from electrochemistry to solar cells [1,2]. In recent years, NiO attracted much attention as an antiferromagnetic (AF) insulator material spintronic devices [3-10]. Understanding the spin - phonon coupling in is a key its functionalization, and enabling AF spintronics' promise of ultra-high-speed low-power dissipation [11,12]. However, despite status exemplary benchmark study correlated electron systems, little...
We report on the thermal and electrical properties of hybrid epoxy composites with graphene boron nitride fillers. The thicknesses, lateral dimensions, aspect ratios each filler material were intentionally selected for geometric similarity to one another, in contrast prior studies that utilized dissimilar geometries achieve a "synergistic" effect. demonstrate electrically-conductive electrically-insulating fillers allow effectively engineer conductivities their resulting composites. By...
We review the current state-of-the-art graphene-enhanced thermal interface materials for management of heat in next generation electronics. Increased integration densities, speed and power electronic optoelectronic devices require with substantially higher conductivity, improved reliability, lower cost. Graphene has emerged as a promising filler material that can meet demands future high-speed high-powered This describes use graphene curing non-curing polymer matrices. Special attention is...
Abstract A method for scalable synthesis of epoxy composites with graphene and few‐layer fillers is described, the electromagnetic interference (EMI) shielding thermal properties such at elevated temperatures are reported. The tested materials reveal excellent total EMI SE T ≈ 65 dB (≈ 105 dB) a thickness 1 mm 2 mm) in X‐band frequency range. At higher filler loading fractions, room‐temperature cross‐plane conductivity 11.2 ± 0.9 Wm −1 K , which factor ×41 larger than that pristine epoxy....
Abstract Development of next‐generation thermal interface materials (TIMs) with high conductivity is important for management and packaging electronic devices. The synthesis measurements noncuring paste, i.e., grease, based on mineral oil a mixture graphene few‐layer flakes as the fillers, reported. paste exhibits distinctive percolation threshold revealing sublinear dependence filler loading. This behavior contrasts curing TIMs, epoxy, where superlinear loading observed. performance...
The magnetic properties in two-dimensional van der Waals materials depend sensitively on structure. CrI3, as an example, has been recently demonstrated to exhibit distinct depending the layer thickness and stacking order. Bulk CrI3 is ferromagnetic (FM) with a Curie temperature of 61 K rhombohedral stacking, whereas few-layer layered antiferromagnetic (AFM) phase lower ordering 45 monoclinic stacking. In this work, we use cryogenic force microscopy investigate flakes intermediate range...
We report results of investigation the phonon and thermal properties exfoliated films layered single crystals antiferromagnetic FePS3 MnPS3 semiconductors. Raman spectroscopy was conducted using three different excitation lasers with wavelengths 325 nm (UV), 488 (blue), 633 (red). UV-Raman reveals spectral features which are not detectable via visible light scattering. The conductivity thin measured by two techniques: steady-state optothermal transient time-resolved magneto-optical Kerr...
Abstract Polymer composite films containing fillers comprising quasi‐1D van der Waals materials, specifically transition metal trichalcogenides with 1D structural motifs that enable their exfoliation into bundles of atomic threads, are reported. These nanostructures characterized by extremely large aspect ratios up to ≈ 10 6 . The polymer composites low loadings TaSe 3 ( < vol%) reveal excellent electromagnetic interference shielding in the X‐band GHz and high frequency sub‐THz ranges,...
The development of cryogenic semiconductor electronics and superconducting quantum computing requires composite materials that can provide both thermal conduction insulation. We demonstrated at temperatures, the conductivity graphene composites be higher lower than reference pristine epoxy, depending on filler loading temperature. There exists a well-defined cross-over temperature-above it, increases with addition graphene; below decreases graphene. counter-intuitive trend was explained by...
Similar to electron waves, the phonon states in semiconductors can undergo changes induced by external boundaries. However, despite strong scientific and practical importance, conclusive experimental evidence of confined acoustic polarization branches individual free-standing nanostructures is lacking. Here we report results Brillouin-Mandelstam light scattering spectroscopy, which reveal multiple (up ten) GaAs nanowires with a diameter as large 128 nm, at length scale that exceeds grey...
We report on the synthesis of epoxy-based composites with graphene fillers and test their electromagnetic shielding efficiency by quasi-optic free-space method in extremely high-frequency (EHF) band (220-325 GHz). The curing adhesive were produced a scalable technique mixture single-layer few-layer layers few-micrometer lateral dimensions. It was found that transmission, T, is low even at small concentrations fillers: T<1% frequency 300 GHz for composite only ϕ = 1 wt% graphene. main...
We report on switching among three charge-density-wave phases, commensurate, nearly incommensurate, and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced by application of an in-plane bias voltage. The all phases has been achieved over a wide temperature range, from 77 to 400 K. low-frequency electronic noise spectroscopy used as effective tool for monitoring transitions, particularly incommensurate metal phase. spectral density exhibits sharp increases at...
A macroscopic film (2.5 cm × 2.5 cm) made by layer-by-layer assembly of 100 single-layer polycrystalline graphene films is reported. The layers are transferred and stacked one using a wet process that leads to layer defects interstitial contamination. Heat-treatment the sample up 2800 °C results in removal contaminants healing defects. resulting freestanding with near-perfect in-plane crystallinity but mixed stacking order through thickness, which separates it from all existing carbon...
Abstract We report the results of polarization‐dependent Raman spectroscopy phonon states in single‐crystalline quasi‐one‐dimensional NbTe 4 and TaTe van der Waals materials. The measurements were conducted wide temperature range from 80 to 560 K. Our show that although both materials have identical crystal structures symmetries, there is a drastic difference intensity their spectra. While exhibits well‐defined peaks through examined wavenumber ranges, reveals extremely weak signatures....
Abstract Low‐frequency current fluctuations, i.e., electronic noise, in quasi‐1D (TaSe 4 ) 2 I Weyl semimetal nanoribbons are discussed. It is found that the noise spectral density of 1/ f type and scales with square current, S ~ ( frequency). The increases by almost an order magnitude develops Lorentzian features near temperature T ≈ 225 K. These changes attributed to charge‐density‐wave phase transition even though maximum deviates from reported Peierls bulk crystals. level, normalized...
We report on the temperature evolution of polarization-dependent Raman spectrum exfoliated MoI$_3$, a van der Waals material with "true one-dimensional" crystal structure that can be to individual atomic chains. The several features reveals anomalous behavior suggesting phase transition magnetic origin. Theoretical considerations indicate MoI$_3$ is an easy-plane antiferromagnet alternating spins along dimerized chains and inter-chain helical spin ordering. calculated frequencies phonons...
We report results of an investigation the temperature dependence magnon and phonon frequencies in NiO. A combination Brillouin - Mandelstam Raman spectroscopies allowed us to elucidate evolution spectral signatures from zone center (GHz range) second-order peaks boundary (THz range). The temperature-dependent behavior bands NiO spectrum indicates presence antiferromagnetic (AF) order fluctuation or a persistent AF state at temperatures above Neel (T=523 K). Tuning intensity excitation laser...