1,721,008 research outputs found
Simulation study of Fermi level depinning in metal-MoS2 contacts
Full text linkWe used Density Functional Theory (DFT) to study the Fermi level pinning and Schottky barrier height in metal-MoS2 contacts. We showed that the Fermi level de-pinning could be attained by controlling the distance between the metal and MoS2. In particular, with proper buffer layers and the use of back-gated structures, the Schottky barrier height can be practically zeroed in some metal-MoS2 stacks, which is important to attain Ohmic contacts
Editorial: Letters from the 8th Joint International EUROSOI workshop and International Conference on Ultimate Integration on Silicon
No full textLimitations to Electrical Probing of Spontaneous Polarization in Ferroelectric-Dielectric Heterostructures
Full text linkAn accurate estimate of the ferroelectric polarization in ferroelectric-dielectric stacks is important from a materials science perspective, and it is also crucial for the development of ferroelectric based electron devices. This paper revisits the theory and application of the PUND technique in Metal-Ferroelectric-Dielectric-Metal (MFDM) structures by using analytical derivations and numerical simulations. In an MFDM structure the results of the PUND technique may largely differ from the polarization actually switched in the stack, which in turn is different from the remnant polarization of the underlying ferroelectric. The main hindrances that prevent PUND measurements from providing a good estimate of the polarization switching in MFDM stacks are thus discussed. The inspection of the involved physical quantities, not always accessible in experiments, provides a useful insight about the main sources of the errors in the PUND technique, and clarifies the delicate interplay between the depolarization field and the charge injection and trapping in MFDM stacks with a thin dielectric layer
Benchmarking of 3-D MOSFET Architectures: Focus on the Impact of Surface Roughness and Self-Heating
Full text linkTremendous improvements in the fabrication
technology have allowed to scale the physical dimensions
of the transistors and also to develop different promising
3-D architectures that may allow continuing Moore’s law.
In this paper, we perform a comparative delay analysis of different
3-D device architectures and study the impact of surface
roughness and self-heating on the on-current using a
comprehensive in-house simulation framework comprising
Schrödinger, Poisson, and Boltzmann transport equation
solvers and comprising relevant scattering mechanisms
and self-heating. Our results highlight that parasitic capacitance
can alter the relative ranking of the architectures from
delay point of view. We demonstrate that surface roughness
can cause architectureand material-dependentcurrent
degradation, and hence, it is necessary to account for it in
simulation-based benchmarking different architectures
Ohmic Behavior in Metal Contacts to n/p-Type Transition-Metal Dichalcogenides: Schottky versus Tunneling Barrier Trade-off
Full text linkHigh contact resistance (RC) between 3D metallic conductors and single-layer 2D semiconductors poses major challenges toward their integration in nanoscale electronic devices. While in experiments the large RC values can be partly due to defects, ab initio simulations suggest that, even in defect-free structures, the interaction between metal and semiconductor orbitals can induce gap states that pin the Fermi level in the semiconductor band gap, increase the Schottky barrier height (SBH), and thus degrade the contact resistance. In this paper, we investigate, by using an in-house-developed ab initio transport methodology that combines density functional theory and nonequilibrium Green’s function (NEGF) transport calculations, the physical properties and electrical resistance of several options for n-type top metal contacts to monolayer MoS2, even in the presence of buffer layers, and for p-type contacts to monolayer WSe2. The delicate interplay between the SBH and tunneling barrier thickness is quantitatively analyzed, confirming the excellent properties of the Bi-MoS2 system as an n-type ohmic contact. Moreover, simulation results supported by literature experiments suggest that the Au-WSe2 system is a promising candidate for p-type ohmic contacts. Finally, our analysis also reveals that a small modulation of a few angstroms of the distance between the (semi)metal and the transition-metal dichalcogenide (TMD) leads to large variations of RC. This could help to explain the scattering of RC values experimentally reported in the literature because different metal deposition techniques can result in small changes of the metal-to-TMD distance besides affecting the density of possible defects
Modelling and Simulations of Ferroelectric Materials and Ferroelectric-Based Nanoelectronic Devices : (Invited Paper)
No full textThis paper provides a brief introduction to the phenomenological aspects of the polarization in ferrroelectric materials, and then an analysis of a few selected topics related to the modelling of ferroelectrics. The description of ferroelectric-based devices is quite challenging, particularly because the ferroelectric is frequently stacked with other dielectrics or with a semiconductor, as opposed to being placed between metal electrodes. Predictive modelling of ferroelectric devices is admittedly difficult, and thus the scrutiny and calibration of the models by comparison to sound experimental data is of paramount importance
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