9,408 research outputs found
Drift-diffusion model for single layer transition metal dichalcogenide field-effect transistors
A physics-based model for the surface potential and drain current for
monolayer transition metal dichalcogenide (TMD) field-effect transistor (FET)
is presented. Taking into account the 2D density-of-states of the atomic layer
thick TMD and its impact on the quantum capacitance, a model for the surface
potential is presented. Next, considering a drift-diffusion mechanism for the
carrier transport along the monolayer TMD, an explicit expression for the drain
current has been derived. The model has been benchmarked with a measured
prototype transistor. Based on the proposed model, the device design window
targeting low-power applications is discussed.Comment: 10 pages, 3 figure
Multi-domain ferroelectricity as a limiting factor for voltage amplification in ferroelectric field-effect transistors
We revise the possibility of having an amplified surface potential in
ferroelectric field-effect transistors pointed out by [S. Salahuddin and S.
Datta, Nano Lett. 8, 405 (2008)]. We show that the negative-capacitance regime
that allows for such an amplification is actually bounded by the appearance of
multi-domain ferroelectricity. This imposes a severe limit to the maximum
step-up of the surface potential obtainable in the device. We indicate new
device design rules taking into account this scenario.Comment: 4 pages, 3 figure
Free Technology Academy : a Joint Venture of Free Software and OER
The decision to publish educational materials openly and under free licenses brings up the challenge of doing it in a sustainable way. Some lessons can be learned from the business models for production, maintenance and distribution of Free and Open Source Software. The Free Technology Academy (FTA) has taken on these challenges and has implemented some of these models. We briefly review the FTA educational programme, methodologies and organisation, and see to which extent these models are proving successful in the case of the FTA
Robust high-capacity audio watermarking based on FFT amplitude modification
This paper proposes a novel robust audio watermarking algorithm to embed data and extract it in a bit-exact manner based on changing the magnitudes of the FFT spectrum. The key point is selecting a frequency band for embedding based on the comparison between the original and the MP3 compressed/decompressed signal and on a suitable scaling factor. The experimental results show that the method has a very high capacity (about 5 kbps), without significant perceptual distortion (ODG about -0.25) and provides robustness against common audio signal processing such as added noise, filtering and MPEG compression (MP3). Furthermore, the proposed method has a larger capacity (number of embedded bits to number of host bits rate) than recent image data hiding methods
Steganalytic Methods for the Detection of Histogram Shifting Data Hiding Schemes
Peer-reviewedIn this paper, several steganalytic techniques designed to detect the existence of hidden messages using histogram shifting schemes are presented. Firstly, three techniques to identify specific histogram shifting data hiding schemes, based on detectable visible alterations on the histogram or abnormal statistical distributions, are suggested. Afterwards, a general technique capable of detecting all the analyzed histogram shifting data hiding methods is suggested. This technique is based on the effect of histogram shifting methods on the ÂżvolatilityÂż of the histogram of the difference image. The different behavior of volatility whenever new data are hidden makes it possible to identify stego and cover images
High capacity audio watermarking using FFT amplitude interpolation
An audio watermarking technique in the frequency domain which takes advantage of interpolation is proposed. Interpolated FFT samples are used to generate imperceptible marks. The experimental results show that the suggested method has very high capacity (about 3kbps), without significant perceptual distortion (ODG about -0.5) and provides robustness against common audio signal processing such as echo, add noise, filtering, resampling and MPEG compression (MP3). Depending on the specific application, the tuning parameters could be selected adaptively to achieve even more capacity and better transparency
Short channel effects in graphene-based field effect transistors targeting radio-frequency applications
Channel length scaling in graphene field effect transistors (GFETs) is key in
the pursuit of higher performance in radio frequency electronics for both rigid
and flexible substrates. Although two-dimensional (2D) materials provide a
superior immunity to Short Channel Effects (SCEs) than bulk materials, they
could dominate in scaled GFETs. In this work, we have developed a model that
calculates electron and hole transport along the graphene channel in a
drift-diffusion basis, while considering the 2D electrostatics. Our model
obtains the self-consistent solution of the 2D Poisson's equation coupled to
the current continuity equation, the latter embedding an appropriate model for
drift velocity saturation. We have studied the role played by the
electrostatics and the velocity saturation in GFETs with short channel lengths
L. Severe scaling results in a high degradation of GFET output conductance. The
extrinsic cutoff frequency follows a 1/L^n scaling trend, where the index n
fulfills n < 2. The case n = 2 corresponds to long-channel GFETs with low
source/drain series resistance, that is, devices where the channel resistance
is controlling the drain current. For high series resistance, n decreases down
to n= 1, and it degrades to values of n < 1 because of the SCEs, especially at
high drain bias. The model predicts high maximum oscillation frequencies above
1 THz for channel lengths below 100 nm, but, in order to obtain these
frequencies, it is very important to minimize the gate series resistance. The
model shows very good agreement with experimental current voltage curves
obtained from short channel GFETs and also reproduces negative differential
resistance, which is due to a reduction of diffusion current.Comment: 27-pages manuscript (10 figures) plus 6 pages of supplementary
information. European Union Action H2020 (696656) / Department
d'Universitats, Recerca i Societat de la Informaci\'o of the Generalitat de
Catalunya (2014 SGR 384) / Ministerio de Econom\'ia y Competitividad of Spain
(TEC2012-31330 and TEC2015-67462-C2-1-R) / MINECO FEDE
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