35 research outputs found
Voltage driven, local, and efficient excitation of nitrogen-vacancy centers in diamond
Magnetic sensing technology has found widespread application in industries as
diverse as transportation, medicine, and resource exploration. Such use cases
often require highly sensitive instruments to measure the extremely small
magnetic fields involved, relying on difficult to integrate Superconducting
Quantum Interference Device (SQUID) and Spin-Exchange Relaxation Free (SERF)
magnetometers. A potential alternative, nitrogen vacancy (NV) centers in
diamond, has shown great potential as a high sensitivity and high resolution
magnetic sensor capable of operating in an unshielded, room-temperature
environment. Transitioning NV center based sensors into practical devices,
however, is impeded by the need for high power RF excitation to manipulate
them. Here we report an advance that combines two different physical phenomena
to enable a highly efficient excitation of the NV centers: magnetoelastic drive
of ferromagnetic resonance (FMR) and NV-magnon coupling. Our work demonstrates
a new pathway to combine acoustics and magnonics that enables highly energy
efficient and local excitation of NV centers without the need for any external
RF excitation, and thus could lead to completely integrated, on-chip, atomic
sensors.Comment: Fixed an issue with the display of figure
Built-in and induced polarization across LaAlO/SrTiO heterojunctions
Ionic crystals terminated at oppositely charged polar surfaces are inherently
unstable and expected to undergo surface reconstructions to maintain
electrostatic stability. Essentially, an electric field that arises between
oppositely charged atomic planes gives rise to a built-in potential that
diverges with thickness. In ultra thin film form however the polar crystals are
expected to remain stable without necessitating surface reconstructions, yet
the built-in potential has eluded observation. Here we present evidence of a
built-in potential across polar \lao ~thin films grown on \sto ~substrates, a
system well known for the electron gas that forms at the interface. By
performing electron tunneling measurements between the electron gas and a
metallic gate on \lao ~we measure a built-in electric field across \lao ~of 93
meV/\AA. Additionally, capacitance measurements reveal the presence of an
induced dipole moment near the interface in \sto, illuminating a unique
property of \sto ~substrates. We forsee use of the ionic built-in potential as
an additional tuning parameter in both existing and novel device architectures,
especially as atomic control of oxide interfaces gains widespread momentum.Comment: 6 pages, 4 figures. Submitted to Nature physics on May 1st, 201
Ultrathin compound semiconductor on insulator layers for high performance nanoscale transistors
Over the past several years, the inherent scaling limitations of electron
devices have fueled the exploration of high carrier mobility semiconductors as
a Si replacement to further enhance the device performance. In particular,
compound semiconductors heterogeneously integrated on Si substrates have been
actively studied, combining the high mobility of III-V semiconductors and the
well-established, low cost processing of Si technology. This integration,
however, presents significant challenges. Conventionally, heteroepitaxial
growth of complex multilayers on Si has been explored. Besides complexity, high
defect densities and junction leakage currents present limitations in the
approach. Motivated by this challenge, here we utilize an epitaxial transfer
method for the integration of ultrathin layers of single-crystalline InAs on
Si/SiO2 substrates. As a parallel to silicon-on-insulator (SOI) technology14,we
use the abbreviation "XOI" to represent our compound semiconductor-on-insulator
platform. Through experiments and simulation, the electrical properties of InAs
XOI transistors are explored, elucidating the critical role of quantum
confinement in the transport properties of ultrathin XOI layers. Importantly, a
high quality InAs/dielectric interface is obtained by the use of a novel
thermally grown interfacial InAsOx layer (~1 nm thick). The fabricated FETs
exhibit an impressive peak transconductance of ~1.6 mS/{\mu}m at VDS=0.5V with
ON/OFF current ratio of greater than 10,000 and a subthreshold swing of 107-150
mV/decade for a channel length of ~0.5 {\mu}m
Dispatchability, energy security, and reduced capital cost in tidal-wind and tidal-solar energy farms
The global tidal energy resource for electricity generation is small, and converting tidal kinetic energy to electricity is expensive compared to solar-photovoltaic or land-based wind turbine generators. However, as the renewable energy content in electricity supplies grows, the need to stabilise these supplies increases. This paper describes tidal energy's potential to reduce intermittency and variability in electricity supplied from solar and wind power farms while lowering the capital expenditure needed to improve dispatchability. The paper provides a model and hypothetical case studies to demonstrate how sharing energy storage between tidal stream power generators and wind or solar power generators can mitigate the level, frequency, and duration of power loss from wind or solar PV farms. The improvements in dispatchability use tidal energy's innate regularity and take account of tidal asymmetry and extended duration low-velocity neap tides. The case studies are based on a national assessment of Australian tidal energy resources carried out from 2018 to 2021
Configuring urban carbon governance: insights from Sydney, Australia
In the political geography of responses to climate change, and the governance of carbon more specifically, the urban has emerged as a strategic site. Although it is recognized that urban carbon governance occurs through diverse programs and projects—involving multiple actors and working through multiple sites, mechanisms, objects, and subjects—surprisingly little attention has been paid to the actual processes through which these diverse elements are drawn together and held together in the exercise of governing. These processes—termed configuration—remain underspecified. This article explores urban carbon governance interventions as relational configurations, excavating how their diverse elements—human, institutional, representational, and material—are assembled, drawn into relation, and held together in the exercise of governing. Through an analysis of two contrasting case studies of urban carbon governance interventions in Sydney, Australia, we draw out common processes of configuring and specific sets of devices and techniques that gather, align, and maintain the relations between actors and elements that constitute intervention projects. We conclude by reflecting on the implications of conceiving of governing projects as relational configurations for how we understand the nature and practice of urban carbon governance, especially by revealing the diverse modes of power at work within processes of configuring
Dispatchability, Energy Security, and Reduced Capital Cost in Tidal-Wind and Tidal-Solar Energy Farms
The global tidal energy resource for electricity generation is small, and converting tidal kinetic energy to electricity is expensive compared to solar-photovoltaic or land-based wind turbine generators. However, as the renewable energy content in electricity supplies grows, the need to stabilise these supplies increases. This paper describes tidal energy’s potential to reduce intermittency and variability in electricity supplied from solar and wind power farms while lowering the capital expenditure needed to improve dispatchability. The paper provides a model and hypothetical case studies to demonstrate how sharing energy storage between tidal stream power generators and wind or solar power generators can mitigate the level, frequency, and duration of power loss from wind or solar PV farms. The improvements in dispatchability use tidal energy’s innate regularity and take account of tidal asymmetry and extended duration low-velocity neap tides. The case studies are based on a national assessment of Australian tidal energy resources carried out from 2018 to 2021