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

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

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

Scale Free Analysis and the Prime Number Theorem

We present an elementary proof of the prime number theorem. The relative error follows a golden ratio scaling law and respects the bound obtained from the Riemann's hypothesis. The proof is derived in the framework of a scale free nonarchimedean extension of the real number system exploiting the concept of relative infinitesimals introduced recently in connection with ultrametric models of Cantor sets. The extended real number system is realized as a completion of the field of rational numbers $Q$ under a {\em new} nonarchimedean absolute value, which treats arbitrarily small and large numbers separately from a finite real number.Comment: AMS-latex 2e, 25 pages, A misprint in the printed paper is correcte

Agricultural Household-Firm Units: Adjustments to Change

This paper assesses agricultural household-firm unit models to determine a useful typology for agricultural policy assessment that draws upon their use. Both standard and bargaining models for analyzing household decisions, including production, consumption, labor, credit, fertility and child schooling, intergenerational transfer, among other key behaviors of households are discussed, as well as data and estimation issues often encountered with household models. Relevant dimensions of a country or region typology are then suggested, focusing on (1) the extent to which markets, particularly labor markets, are perfect, missing or mixed; (2) relevant intra-household and key demographic considerations; and (3) the differentiation of particular household-firm units that are particularly disadvantaged and may be of the most critical policy concern.agricultural households, farm households, labor, labor adjustments, off-farm employment, Consumer/Household Economics, Labor and Human Capital,

STRESS AMONG FARM WOMEN:AN ANALYSIS OF FARM HOUSEHOLDS IN PENNSYLVANIA

Farming is among the high-stress occupations in the United States and farm women have higher stress scores due to multiple job holdings. The study investigates the determinants of time stress experienced by farm women in Pennsylvania applying an economic model of stress developed by Hamermesh and Lee (2003).Farm Management,

Women in Science: Surpassing Subtle and Overt Biases through Intervention Programs

This study discusses factors that keep women from entering science and technology, which include social stereotypes that they struggle against, lack of maternity leave and other basic human rights, and the climate that makes them leave research positions for administrative ones. We then describe intervention processes that have been successful in bringing the ratio of women close to parity, compare different minorities in the US, and also consider data from India, Western and Eastern Europe. We find that programs that connect the different levels of education are needed in addition to hiring more women, providing them with basic human rights from when they begin their PhD onwards and promoting support networks for existing employees. The authors of this paper hail from Sri Lanka, Romania, India, and the United States. We hold undergraduate and graduate degrees in physics or chemistry from the United States, India and Switzerland. Our conclusions are based on data that is publicly available, on data we have gathered, and on anecdotal evidence from our own experience.Comment: Submitted to the Frontiers Journal as part of the Women in Science Research Topi