248 research outputs found
Enhanced interlayer neutral excitons and trions in trilayer van der Waals heterostructures
Vertically stacked van der Waals heterostructures constitute a promising
platform for providing tailored band alignment with enhanced excitonic systems.
Here we report observations of neutral and charged interlayer excitons in
trilayer WSe2-MoSe2-WSe2 van der Waals heterostructures and their dynamics. The
addition of a WSe2 layer in the trilayer leads to significantly higher
photoluminescence quantum yields and tunable spectral resonance compared to its
bilayer heterostructures at cryogenic temperatures. The observed enhancement in
the photoluminescence quantum yield is due to significantly larger
electron-hole overlap and higher light absorbance in the trilayer
heterostructure, supported via first-principle pseudopotential calculations
based on spin-polarized density functional theory. We further uncover the
temperature- and power-dependence, as well as time-resolved photoluminescence
of the trilayer heterostructure interlayer neutral excitons and trions. Our
study elucidates the prospects of manipulating light emission from interlayer
excitons and designing atomic heterostructures from first-principles for
optoelectronics.Comment: 25 pages, 5 figures(Maintext). 9 pages, 7 figures(Supplementary
Information). - Accepted for publication in npg: 2D materials and
applications and reformatted to its standard. - Updated co-authors and
references. - Title and abstract are modified for clarity. - Errors have been
corrected, npg: 2D materials and applications (2018
First-principles study of oxygen vacancy defects in orthorhombic HfZrO/SiO/Si gate stack
The gate defect of the ferroelectric HfO-based Si field-effect transistor
(Si FeFET) plays a dominant role in its reliability issue. The first-principles
calculations are an effective method for the atomic-scale understanding of gate
defects. However, the first-principles study on the defects of FeFET gate
stacks, i.e., metal/orthorhombic-HfZrO/SiO/Si
structure, has not been reported so far. The key challenge is the construction
of metal/orthorhombic-HfZrO/SiO/Si gate stack models.
Here, we use the HfZrO(130) high-index crystal face as the
orthorhombic ferroelectric layer and construct a robust atomic structure of the
orthorhombic-HfZrO/SiO/Si gate stack without any gap
states. Its high structural stability is ascribed to the insulated interface.
The calculated band offsets show that this gate structure is of the type-I band
alignment. Furthermore, the formation energies and charge transition levels
(CTLs) of defects reveal that the oxygen vacancy defects are more favorable to
form compared with other defects such as oxygen interstitial and Hf/Zr vacancy,
and their CTLs are mainly localized near the Si conduction band minimum and
valence band maximum, in agreement with the reported experimental results. The
oxygen vacancy defects are responsible for charge trapping/de-trapping behavior
in Si FeFET. This work provides an insight into gate defects and paves the way
to carry out the first-principles study of ferroelectric HfO-based Si
FeFET.Comment: 18 pages, 5 figure
PASNet: Polynomial Architecture Search Framework for Two-party Computation-based Secure Neural Network Deployment
Two-party computation (2PC) is promising to enable privacy-preserving deep
learning (DL). However, the 2PC-based privacy-preserving DL implementation
comes with high comparison protocol overhead from the non-linear operators.
This work presents PASNet, a novel systematic framework that enables low
latency, high energy efficiency & accuracy, and security-guaranteed 2PC-DL by
integrating the hardware latency of the cryptographic building block into the
neural architecture search loss function. We develop a cryptographic hardware
scheduler and the corresponding performance model for Field Programmable Gate
Arrays (FPGA) as a case study. The experimental results demonstrate that our
light-weighted model PASNet-A and heavily-weighted model PASNet-B achieve 63 ms
and 228 ms latency on private inference on ImageNet, which are 147 and 40 times
faster than the SOTA CryptGPU system, and achieve 70.54% & 78.79% accuracy and
more than 1000 times higher energy efficiency.Comment: DAC 2023 accepeted publication, short version was published on AAAI
2023 workshop on DL-Hardware Co-Design for AI Acceleration: RRNet: Towards
ReLU-Reduced Neural Network for Two-party Computation Based Private Inferenc
Corrigendum to: The TianQin project: current progress on science and technology
In the originally published version, this manuscript included an error related to indicating the corresponding author within the author list. This has now been corrected online to reflect the fact that author Jun Luo is the corresponding author of the article
Rivulet formulation in the flow of film down a uniformly heated vertical substrate
Three-dimensional regularized weighted residuals model is developed to study vertical falling film on a uniformly substrate with constant heat flux. The model is verified through linear stability analyses in both the stream and the span directions. It is shown that rivulet formation is due to the dominance of the thermocapillary Marangoni effect in the span direction, i.e., the component in the span direction of the surface temperature gradient is much larger than the component in the stream direction, which results from the different heat transfer modes in the stream and the span directions. Four types of initial disturbance are separately imposed on the film flow. It is shown that the initial disturbance does have an influence on the rivulet formation process, but it has no effect on the eventual film structure. Rivulet formation on the film enhances the heat transfer on a wavy film surface, which is attributed for the most part to the increase in the surface area of the film. On the effect of the Reynolds and the Marangoni numbers on rivulet formation, an increase in the former results in an increase in rivulet width, while an increase in the latter causes an advance in the film rupture
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