27 research outputs found
Vanadium Dioxide Circuits Emulate Neurological Disorders
Information in the central nervous system (CNS) is conducted via electrical signals known as action potentials and is encoded in time. Several neurological disorders including depression, Attention Deficit Hyperactivity Disorder (ADHD), originate in faulty brain signaling frequencies. Here, we present a Hodgkin-Huxley model analog for a strongly correlated VO2 artificial neuron system that undergoes an electrically-driven insulator-metal transition. We demonstrate that tuning of the insulating phase resistance in VO2 threshold switch circuits can enable direct mimicry of neuronal origins of disorders in the CNS. The results introduce use of circuits based on quantum materials as complementary to model animal studies for neuroscience, especially when precise measurements of local electrical properties or competing parallel paths for conduction in complex neural circuits can be a challenge to identify onset of breakdown or diagnose early symptoms of disease
Nanosecond electron imaging of transient electric fields and material response
Electrical pulse stimulation drives many important physical phenomena in
condensed matter as well as in electronic systems and devices. Often,
nanoscopic and mesoscopic mechanisms are hypothesized, but methods to image
electrically driven dynamics on both their native length and time scales have
so far been largely undeveloped. Here, we present an ultrafast electron
microscopy approach that uses electrical pulses to induce dynamics and records
both the local time-resolved electric field and corresponding material behavior
with nanometer-nanosecond spatiotemporal resolution. Quantitative measurement
of the time-dependent field via the electron beam deflection is demonstrated by
recording the field between two electrodes with single-ns temporal resolution.
We then show that this can be applied in a material by correlating applied
field with resulting dynamics in TaS. First, time-resolved electron
diffraction is used to simultaneously record the electric field and crystal
structure change in a selected region during a 20 ns voltage pulse, showing how
a charge density wave transition evolves during and after the applied field.
Then, time-resolved nanoimaging is demonstrated, revealing heterogeneous
distortions that occur in the freestanding flake during a longer, lower
amplitude pulse. Altogether, these results pave the way for future experiments
that will uncover the nanoscale dynamics underlying electrically driven
phenomena.Comment: Main article: 7 pages, 3 figures. Supplemental Material: 8 pages, 7
figure
Quasi-deterministic Localization of Er Emitters in Thin Film TiO through Submicron-scale Crystalline Phase Control
With their shielded 4f orbitals, rare-earth ions (REIs) offer optical and
electron spin transitions with good coherence properties even when embedded in
a host crystal matrix, highlighting their utility as promising quantum emitters
and memories for quantum information processing. Among REIs, trivalent erbium
(Er) uniquely has an optical transition in the telecom C-band, ideal for
transmission over optical fibers, and making it well-suited for applications in
quantum communication. The deployment of Er emitters into a thin film
TiO platform has been a promising step towards scalable integration;
however, like many solid-state systems, the deterministic spatial placement of
quantum emitters remains an open challenge. We investigate laser annealing as a
means to locally tune the optical resonance of Er emitters in TiO
thin films on Si. Using both nanoscale X-ray diffraction measurements and
cryogenic photoluminescence spectroscopy, we show that tightly focused
below-gap laser annealing can induce anatase to rutile phase transitions in a
nearly diffraction-limited area of the films and improve local crystallinity
through grain growth. As a percentage of the Er:TiO is converted to rutile,
the Er optical transition blueshifts by 13 nm. We explore the effects of
changing laser annealing time and show that the amount of optically active
Er:rutile increases linearly with laser power. We additionally demonstrate
local phase conversion on microfabricated Si structures, which holds
significance for quantum photonics.Comment: 7 pages, 4 figure
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Integration of silicon chip microstructures for in-line microbial cell lysis in soft microfluidics
The paper presents fabrication methodologies that integrate silicon components into soft microfluidic devices to perform microbial cell lysis for biological applications. The integration methodology consists of a silicon chip that is fabricated with microstructure arrays and embedded in a microfluidic device, which is driven by piezoelectric actuation to perform cell lysis by physically breaking microbial cell walls via micromechanical impaction. We present different silicon microarray geometries, their fabrication techniques, integration of said micropatterned silicon impactor chips into microfluidic devices, and device operation and testing on synthetic microbeads and two yeast species (S. cerevisiae and C. albicans) to evaluate their efficacy. The generalized strategy developed for integration of the micropatterned silicon impactor chip into soft microfluidic devices can serve as an important process step for a new class of hybrid silicon-polymeric devices for future cellular processing applications. The proposed integration methodology can be scalable and integrated as an in-line cell lysis tool with existing microfluidics assays
Accelerating Materials Development via Automation, Machine Learning, and High-Performance Computing
Successful materials innovations can transform society. However, materials
research often involves long timelines and low success probabilities,
dissuading investors who have expectations of shorter times from bench to
business. A combination of emergent technologies could accelerate the pace of
novel materials development by 10x or more, aligning the timelines of
stakeholders (investors and researchers), markets, and the environment, while
increasing return-on-investment. First, tool automation enables rapid
experimental testing of candidate materials. Second, high-throughput computing
(HPC) concentrates experimental bandwidth on promising compounds by predicting
and inferring bulk, interface, and defect-related properties. Third, machine
learning connects the former two, where experimental outputs automatically
refine theory and help define next experiments. We describe state-of-the-art
attempts to realize this vision and identify resource gaps. We posit that over
the coming decade, this combination of tools will transform the way we perform
materials research. There are considerable first-mover advantages at stake,
especially for grand challenges in energy and related fields, including
computing, healthcare, urbanization, water, food, and the environment.Comment: 22 pages, 3 figure
Anomalous Purcell decay of strongly driven inhomogeneous emitters coupled to a cavity
We perform resonant fluorescence lifetime measurements on a
nanocavity-coupled erbium ensemble as a function of cavity-laser detuning and
pump power. Our measurements reveal an anomalous suppression of the ensemble
decay lifetime at zero cavity detuning and high pump fluence. We capture
qualitative aspects of this decay rate suppression using a Tavis-Cummings model
of non-interacting spins coupled to a common cavity.Comment: 4 figure
Purcell enhancement of erbium ions in TiO on silicon nanocavities
Isolated solid-state atomic defects with telecom optical transitions are
ideal quantum photon emitters and spin qubits for applications in long-distance
quantum communication networks. Prototypical telecom defects such as erbium
suffer from poor photon emission rates, requiring photonic enhancement using
resonant optical cavities. Many of the traditional hosts for erbium ions are
not amenable to direct incorporation with existing integrated photonics
platforms, limiting scalable fabrication of qubit-based devices. Here we
present a scalable approach towards CMOS-compatible telecom qubits by using
erbium-doped titanium dioxide thin films grown atop silicon-on-insulator
substrates. From this heterostructure, we have fabricated one-dimensional
photonic crystal cavities demonstrating quality factors in excess of
and corresponding Purcell-enhanced optical emission rates of
the erbium ensembles in excess of 200. This easily fabricated materials
platform represents an important step towards realizing telecom quantum
memories in a scalable qubit architecture compatible with mature silicon
technologies.Comment: 3 figure
Nanocavity-mediated Purcell enhancement of Er in TiO thin films grown via atomic layer deposition
The use of trivalent erbium (Er), typically embedded as an atomic
defect in the solid-state, has widespread adoption as a dopant in
telecommunications devices and shows promise as a spin-based quantum memory for
quantum communication. In particular, its natural telecom C-band optical
transition and spin-photon interface makes it an ideal candidate for
integration into existing optical fiber networks without the need for quantum
frequency conversion. However, successful scaling requires a host material with
few intrinsic nuclear spins, compatibility with semiconductor foundry
processes, and straightforward integration with silicon photonics. Here, we
present Er-doped titanium dioxide (TiO) thin film growth on silicon
substrates using a foundry-scalable atomic layer deposition process with a wide
range of doping control over the Er concentration. Even though the as-grown
films are amorphous, after oxygen annealing they exhibit relatively large
crystalline grains, and the embedded Er ions exhibit the characteristic optical
emission spectrum from anatase TiO. Critically, this growth and annealing
process maintains the low surface roughness required for nanophotonic
integration. Finally, we interface Er ensembles with high quality factor Si
nanophotonic cavities via evanescent coupling and demonstrate a large Purcell
enhancement (300) of their optical lifetime. Our findings demonstrate a
low-temperature, non-destructive, and substrate-independent process for
integrating Er-doped materials with silicon photonics. At high doping densities
this platform can enable integrated photonic components such as on-chip
amplifiers and lasers, while dilute concentrations can realize single ion
quantum memories.Comment: 5 figure