Prospects of Zero Schottky Barrier Height in a Graphene Inserted MoS2-Metal Interface

A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS2 channel based field-effect transistors. Approaches such as choosing metals with appropriate work functions and chemical doping are employed previously to improve the carrier injection from the contact electrodes to the channel and to mitigates the SBH between the MoS2 and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS2. However, the physical or chemical origin of this phenomenon is not yet clearly understood. In this work, density functional theory (DFT) simulations are performed, employing pseudopotentials with very high basis sets to get insights of the charge transfer between metal and monolayer MoS2 through the inserted graphene layer. Our atomistic simulations on 16 different interfaces involving five different metals (Ti, Ag, Ru, Au and Pt) reveal that: (i) such a decrease in SBH is not consistent among various metals, rather an increase in SBH is observed in case of Au and Pt (ii) unlike MoS2-metal interface, the projected dispersion of MoS2 remains preserved in any MoS2-graphene-metal system with shift in the bands on the energy axis. (iii) a proper choice of metal (e.g., Ru) may exhibit ohmic nature in a graphene inserted MoS2-metal contact. These understandings would provide a direction in developing high performance transistors involving hetero atomic layers as contact electrodes.Comment: 8 pages, 6 figures Accepted in Journal of Applied Physic

First Principles Study of Metal Contacts to Monolayer Black Phosphorous

Atomically thin layered black phosphorous (BP) has recently appeared as an alternative to the transitional metal di chalcogenides for future channel material in a MOS transistor due to its lower carrier effective mass. Investigation of the electronic property of source/drain contact involving metal and two-dimensional material is essential as it impacts the transistor performance. In this paper we perform a systematic and rigorous study to evaluate the Ohmic nature of the side-contact formed by the monolayer BP (mBP) and metals (gold, titanium and palladium), which are commonly used in experiments. Employing the Density Functional Theory (DFT), we analyse the potential barrier, charge transfer and atomic orbital overlap at the metal-mBP interface in an optimized structure to understand how efficiently carriers could be injected from metal contact to the mBP channel. Our analysis shows that gold forms a Schottky contact with a higher tunnel barrier at the interface in comparison to the titanium and palladium. mBP contact with palladium is found to be purely Ohmic, where as titanium contact demonstrates an intermediate behaviour.Comment: 10 Pages 13 Figures Accepted in Journal Of Applied Physic

Analysis of Vacancy defects in Hybrid Graphene-Boron Nitride Armchair Nanoribbon based n-MOSFET at Ballistic Limit

Here, we report the performance of vacancy affected supercell of a hybrid Graphene-Boron Nitride embedded armchair nanoribbon (a-GNR-BN) based n-MOSFET at its ballistic transport limit using Non Equilibrium Green's Function (NEGF) methodology. A supercell is made of the 3p configuration of armchair nanoribbon that is doped on the either side with 6 BN atoms and is also H-passivated. The type of vacancies studied are mono (B removal), di (B and N atom removal) and hole (removal of 6 atoms) formed all at the interface of carbon and BN atoms. Density Functional Theory (DFT) is employed to evaluate the material properties of this supercell like bandgap, effective mass and density of states (DOS). Further band gap and effective mass are utilized in self-consistent PoissonSchrodinger calculator formalized using NEGF approach. For all the vacancy defects, material properties show a decrease which is more significant for hole defects. This observation is consistent in the device characteristics as well where ON-current (ION ) and Sub Threshold Slope (SS) shows the maximum increment for hole vacancy and increase is more significant becomes when the number of defects increase.Comment: in 18th International Workshop on Computational Electronics (2015

How to mobilize public resources to support poverty reduction:

Hunger, Developing countries, Agricultural spending, Government spending, Poverty reduction, Strategies in public spending, Increasing efficiency, Public investment,

Evolution of Co-operation When the Strategies are Hidden: The Human Mating Game

Defection is frequently seen in co-operative systems [1-3]. Game theoretical solutions to stabilize cooperation rely on reciprocity and reputation in iterated games[4-5]. One of the basic requirements for reciprocity or reputation building is that the strategies of players and the resulting payoffs should be open at the end of every interaction. For games in which the strategies and payoffs remain hidden, these stabilizing factors are unlikely to work. We examine the evolution of cooperation for hidden-strategy games using human mating game as an example. Here faithful parenting can be considered as cooperation and extra-pair mating (EPM) or cuckoldry as defection. Cuckoldry may get exposed only occasionally and the genetic benefits of cuckoldry also remain hidden from the players. Along with mate guarding, social policing is enabled in humans by language and gossiping. However, social policing can be invaded by second order free riders. We suggest that opportunistic blackmailing, which is unique to hidden strategy games can act as a keystone strategy in stabilizing co-operation. This can counteract free riding and stabilize policing. A game theoretical model results into a rock - paper – scissor (R-P-S) like situation with no evolutionary stable strategy (ESS). Simulations result into a stable or stably oscillating polymorphism. Obligate monogamy is an essential trait in the co-existence. In a gender difference model too, polymorphism is seen in both genders but with different traits predominating in the two genders. The model explains intra-gender, inter-gender as well as cross cultural variability in mating strategies in humans

Shrewd Selection Speeds Surfing: Use Smart EXP3!

In this paper, we explore the use of multi-armed bandit online learning techniques to solve distributed resource selection problems. As an example, we focus on the problem of network selection. Mobile devices often have several wireless networks at their disposal. While choosing the right network is vital for good performance, a decentralized solution remains a challenge. The impressive theoretical properties of multi-armed bandit algorithms, like EXP3, suggest that it should work well for this type of problem. Yet, its real-word performance lags far behind. The main reasons are the hidden cost of switching networks and its slow rate of convergence. We propose Smart EXP3, a novel bandit-style algorithm that (a) retains the good theoretical properties of EXP3, (b) bounds the number of switches, and (c) yields significantly better performance in practice. We evaluate Smart EXP3 using simulations, controlled experiments, and real-world experiments. Results show that it stabilizes at the optimal state, achieves fairness among devices and gracefully deals with transient behaviors. In real world experiments, it can achieve 18% faster download over alternate strategies. We conclude that multi-armed bandit algorithms can play an important role in distributed resource selection problems, when practical concerns, such as switching costs and convergence time, are addressed.Comment: Full pape

Realising a signature verification using Single Electron Transport Devices.

The need for developing faster systems are a trend today. Binary decision devices, working on the principle of single electrons are much faster and low time consuming. This paper aims at realizing a system of signature verification using single electron transistors. Single electron transistors can be used as binary decision devices to create logic gates, flip-flops etc. These logic circuit components will be employed to realize a signature verification system. The advantage of single electron transistor is its compact size and low power requirement. Also, single electron transistors have a much faster switching speed. Hence, SETs can be said to be the electronic equipments of the future. Their application in an offline signature verification device would help create a system that is fast, robust and low power consuming. Signature is an important tool to validate one’s identity. This project would help in creating a device that would verify the authenticity of a signature using the SETs