7 research outputs found
Phase change dynamics and 2-dimensional 4-bit memory in Ge2Sb2Te5 via telecom-band encoding
As modern computing gets continuously pushed up against the von Neumann
Bottleneck -- limiting the ultimate speeds for data transfer and computation --
new computing methods are needed in order to bypass this issue and keep our
computer's evolution moving forward, such as hybrid computing with an optical
co-processor, all-optical computing, or photonic neuromorphic computing. In any
of these protocols, we require an optical memory: either a
multilevel/accumulator memory, or a computational memory. Here, we propose and
demonstrate a 2-dimensional 4-bit fully optical non-volatile memory using
Ge2Sb2Te5 (GST) phase change materials, with encoding via a 1550 nm laser.
Using the telecom-band laser, we are able to reach deeper into the material due
to the low-loss nature of GST at this wavelength range, hence increasing the
number of optical write/read levels compared to previous demonstrations, while
simultaneously staying within acceptable read/write energies. We verify our
design and experimental results via rigorous numerical simulations based on
finite element and nucleation theory, and we successfully write and read a
string of characters using direct hexadecimal encoding
Thermal and Manufacturing Design Considerations for Silicon-Based Embedded Microchannel-Three-Dimensional Manifold CoolersâPart 2: Parametric Study of EMMCs for High Heat Flux (âŒ1âkW/cm2) Power Electronics Cooling
Unveiling the Effect of Superlattice Interfaces and Intermixing on Phase Change Memory Performance
Superlattice (SL) phase change materials have shown promise to reduce the switching current and resistance drift of phase change memory (PCM). However, the effects of internal SL interfaces and intermixing on PCM performance remain unexplored, although these are essential to understand and ensure reliable memory operation. Here, using nanometer-thin layers of Ge2Sb2Te5 and Sb2Te3 in SL-PCM, we uncover that both switching current density (J(reset)) and resistance drift coefficient (v) decrease as the SL period thickness is reduced (i.e., higher interface density); however, interface intermixing within the SL increases both. The signatures of distinct versus intermixed interfaces also show up in transmission electron microscopy, X-ray diffraction, and thermal conductivity measurements of our SL films. Combining the lessons learned, we simultaneously achieve low J(reset) & AP; 3-4 MA/ cm(2) and ultralow v & AP; 0.002 in mushroom-cell SL-PCM with similar to 110 nm bottom contact diameter, thus advancing SL-PCM for and neuromorphic applications
Tungsten-doped Ge2Sb2Te5 phase change material for high-speed optical switching devices
The large impedance mismatch between the highly resistive amorphous state and the highly conductive crystalline state of Ge 2 Sb 2 Te 5 is an impediment for the realization of high-speed electrically switched optical devices. In this paper, we demonstrate that tungsten doping can reduce this resistivity contrast and also results in a lower amorphous state resistivity. Additionally, it lowers the contact resistance, improves the optical contrast, and extends the face-centered-cubic state up to 35 0 ° C, with a minimal impact on thermal conductivity
Direct Visualization of Thermal Conductivity Suppression Due to Enhanced Phonon Scattering Near Individual Grain Boundaries
Understanding
the impact of lattice imperfections on nanoscale
thermal transport is crucial for diverse applications ranging from
thermal management to energy conversion. Grain boundaries (GBs) are
ubiquitous defects in polycrystalline materials, which scatter phonons
and reduce thermal conductivity (Îș). Historically, their impact
on heat conduction has been studied indirectly through spatially averaged
measurements, that provide little information about phonon transport
near a single GB. Here, using spatially resolved time-domain thermoreflectance
(TDTR) measurements in combination with electron backscatter diffraction
(EBSD), we make localized measurements of Îș within few ÎŒm
of individual GBs in boron-doped polycrystalline diamond. We observe
strongly suppressed thermal transport near GBs, a reduction in Îș
from âŒ1000 W m<sup>â1</sup> K<sup>â1</sup> at
the center of large grains to âŒ400 W m<sup>â1</sup> K<sup>â1</sup> in the immediate vicinity of GBs. Furthermore, we
show that this reduction in Îș is measured up to âŒ10 ÎŒm
away from a GB. A theoretical model is proposed that captures the
local reduction in phonon mean-free-paths due to strongly diffuse
phonon scattering at the disordered grain boundaries. Our results
provide a new framework for understanding phononâdefect interactions
in nanomaterials, with implications for the use of high-Îș polycrystalline
materials as heat sinks in electronics thermal management