Development of Hierarchical Simulation Framework for Design and Optimization of Molecular Based Flash Cell

The field of molecular electronics continues to spur interest in the quest for miniaturization and reduction of operational power of electron devices. Most of the systems described in the literature are based on organic molecules, such as benzene, ferrocene and fullerenes [1]. However, the use of inorganic molecules known as polyoxometalates (POMs) (see Fig. 1 and Fig. 2) could offer several important advantages over the conventional and organic based devices. The interest in POMs for flash cell applications stems from the fact that POMs are highly redox active molecules and that they can also be doped with electronically active heteroatoms [3]. They can undergo multiple reversible reductions/oxidations, which makes them attractive candidates for multi-bit storage in flash memory cells. Our recent work showed that POMs are more compatible with existing CMOS processes than organic molecules and they can replace the polysilicon floating gate in contemporary flash cell devices [2]. In this work, we discuss a further improvement and development of our simulation framework and models, e.g. Poisson distribution of the molecules in the oxide, introducing a various device geometry such as FDSOI and nanowires and improved simulation flow

First Principle Simulations of Electronic and Optical Properties of a Hydrogen Terminated Diamond Doped by a Molybdenum Oxide Molecule

In this work we investigate the surface transfer doping process induced between a hydrogen-terminated (100) diamond and a metal oxide MoO 3 , using the Density Functional Theory (DFT) method. DFT allows us to calculate the electronic and optical properties of the hydrogen-terminated diamond (H-diamond) and establish a link between the underlying electronic structure and the charge transfer between the oxide materials and the H-diamond. Our results show that the metal oxide molecule can be described as an electron acceptor and extracts the electrons from the diamond creating 2D hole gas in the diamond surface. Hence, this metal oxide molecule acts as a p-type doping material for the diamond

Electronic and Optical Properties of Hydrogen-Terminated Diamond Doped by Molybdenum Oxide: A Density Functional Theory Study

In this work we investigate the surface transfer doping process induced between a hydrogen-terminated (100) diamond and a metal oxide MoO 3 , using the Density Functional Theory (DFT) method. Using DFT, we have calculated the electronic and optical properties of the hydrogen-terminated diamond and established a link between the underlying electronic structure and the charge transfer between the oxide materials and the hydrogen-terminated diamond. Our results show that the metal oxide can be described as an electron acceptor and extracts the electrons from the diamond creating 2D hole gas in the diamond surface. Hence, this metal oxide acts as a p-type doping material for the diamond

Simulation study of surface transfer doping of hydrogenated diamond by MoO₃ and V₂O₅ metal oxides

In this work, we investigate the surface transfer doping process that is induced between hydrogen-terminated (100) diamond and the metal oxides, MoO₃ and V₂O₅, through simulation using a semi-empirical Density Functional Theory (DFT) method. DFT was used to calculate the band structure and charge transfer process between these oxide materials and hydrogen terminated diamond. Analysis of the band structures, density of states, Mulliken charges, adsorption energies and position of the Valence Band Minima (VBM) and Conduction Band Minima (CBM) energy levels shows that both oxides act as electron acceptors and inject holes into the diamond structure. Hence, those metal oxides can be described as p-type doping materials for the diamond. Additionally, our work suggests that by depositing appropriate metal oxides in an oxygen rich atmosphere or using metal oxides with high stochiometric ration between oxygen and metal atoms could lead to an increase of the charge transfer between the diamond and oxide, leading to enhanced surface transfer doping

The First-Priniple Simulation Study on the Specific Grain Boundary Resistivity in Copper Interconnects

In this work, we present a systematic simulation study of numerous copper (Cu) grain boundaries with the nonequilibrium Green's function (NEGF) framework based on the Density Functional Theory (DFT). In order to evaluate the effect of specific resistivity of various grain boundary profiles we developed the required methodology and we proposed an analytical equation for predicting the specific resistivity at each GB configuration. Moreover, in this work we also considered different crystal transport orientations and coincidence site lattices. Based on our simulations, we found that the specific grain boundary resistivity strongly depends on the transport orientations of the grains but not on the coincidence site lattice (CSL) density

Simulations of Surface Transfer Doping of Hydrogenated Diamond by MoO3 Metal Oxide

In this work we investigate the surface transfer doping effect induced between hydrogen terminated diamond and Moo3. We simulated the interface of (100) MoO 3 surface and hydrogen terminated (100) diamond surface using fist principle methods such as Density Functional Theory (DFT). DFT simulation allowed us to calculate the band structure and charge transfer between the MoO 3 and the diamond materials. Analysis of the band structures and density of states shows that the Moo3is an electron acceptor and injects holes into the diamond structure

A Hierarchical Model for CNT and Cu-CNT Composite Interconnects: From Density Functional Theory to Circuit-Level Simulations

No abstract available

Interaction Between Precisely Placed Dopants and Interface Roughness in Silicon Nanowire Transistors: Full 3-D NEGF Simulation Study

In this work, we report a theoretical study based on quantum transport simulations that show the impact of the surface roughness on the performance of ultimately scaled gate-all-around silicon nanowire transistors (SNWT) with precisely positioned dopants designed for digital circuit applications. Due to strong inhomogeneity of the self-consistent electrostatic potential, a full 3-D real-space Non Equilibrium Green's Function (NEGF) formalism is used. The individual dopants and the profile of the channel surface roughness act as localized scatters and, hence, the impact on the electron transport is directly correlated to the combined effect of position of the single dopants and surface roughness shape. As a result, a large variation in the IOFF and ION and modest variation of the subthreshold slope are observed in the ID-VG characteristics when comparing devices without surface roughness. The variations of the current-voltage characteristics are analyzed with reference to the behaviour of the transmission coefficients, electron potential and electron concentration along the length of the device. Our calculations provide guidance for a future development of the next generation components with sub-10 nm dimensions for the semiconductor industry

Optimization and evaluation of variability in the programming window of a flash cell with molecular metal-oxide storage

We report a modeling study of a conceptual nonvolatile memory cell based on inorganic molecular metal-oxide clusters as a storage media embedded in the gate dielectric of a MOSFET. For the purpose of this paper, we developed a multiscale simulation framework that enables the evaluation of variability in the programming window of a flash cell with sub-20-nm gate length. Furthermore, we studied the threshold voltage variability due to random dopant fluctuations and fluctuations in the distribution of the molecular clusters in the cell. The simulation framework and the general conclusions of our work are transferrable to flash cells based on alternative molecules used for a storage media

Molecular Based Flash Cell for Low Power Flash Application: Optimization and Variability Evaluation

The field of molecular electronics continues to spur interest in the quest for miniaturization and reduction of operational power of electron devices. Most of the systems described in the literature are based on organic molecules, such as benzene, ferrocene and fullerenes. However, the use of inorganic molecules known as polyoxometalates (POMs) (see Fig.l and Fig.2) could offer several important advantages over the conventional and organic based devices. Our present work shows that POMs are more compatible with existing CMOS processes than organic molecules and they can replace the polysilicon floating gate in contemporary flash cell devices [2]. The interest in POMs for flash cell applications stems from the fact that POMs are highly redox active molecules and that they can also be doped with electronically active heteroatoms [3]. They can undergo multiple reversible reductions/oxidations, which makes them attractive candidates for multi-bit storage in flash memory cells. The molecular charge storage is localised, thus minimising cross-cell capacitive coupling, which arises from charge redistribution on the sides of a poly-Si floating gate (FG) and is one of the most critical issues with flash memories. Although this benefit is presently realised in floating gates by charge-trapping dielectric or by a metallic nano-cluster array, both technologies exhibit large variability. Charge-trap memories suffer variation in trap-density and trap energy and the size and density of nano-clusters is difficult to control. This precludes their ultimate miniaturization. In fact, the concept of using molecules as storage centers has already been demonstrated for organic redox-active molecules [1]. Here, using full 3D simulations, we evaluate correlation between the device performance (in terms of threshold voltage VT) and statistical variability, arising from the random dopant fluctuations (RDF) and POM fluctuations (POMF)