Ohmic Behavior in Metal Contacts to n/p-Type Transition-Metal Dichalcogenides: Schottky versus Tunneling Barrier Trade-off

High 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

Electrochemical surface engineering of magnesium metal by plasma electrolytic oxidation and calcium phosphate deposition: biocompatibility and in vitro degradation studies

In this study, the surface of magnesium metal was electrochemically engineered for enhanced biocompatibility and controlled degradation in body fluid. Firstly, a plasma electrolytic oxidation (PEO) coating was formed on magnesium, followed by electrochemical deposition of calcium phosphate (CaP) using an unconventional electrolyte. Cytocompatibility tests using L929 cells revealed that the PEO-CaP coating significantly improved the biocompatibility of magnesium. In vitro electrochemical degradation experiments in simulated body fluid (SBF) showed that the PEO-CaP coating improved the degradation resistance of magnesium significantly. The corrosion current density (i(corr)) of the PEO-CaP coated magnesium was approximate to 99% and approximate to 97% lower than that of bare magnesium and the PEO-only coated magnesium, respectively. Similarly, electrochemical impedance spectroscopy (EIS) results showed that the polarisation resistance (R-P) of the PEO-CaP coated magnesium was one-order of magnitude higher as compared to the PEO-only coated magnesium and two-orders of magnitude higher than the bare magnesium, after 72 h immersion in SBF. Scanning electron microscopy (SEM) analysis revealed no localized degradation in the PEO-CaP coated magnesium. The study demonstrated that the PEO-CaP coating is a promising combination for enhancing the biocompatibility and reducing the degradation of magnesium for potential biodegradable implant applications

DFT study of graphene doping due to metal contacts

The experimental results of Metal\u2013graphene (M\u2013G) contact resistance (RC) have been investigated in\u2013depth by means of Density Functional Theory (DFT). The simulations allowed us to build a consistent picture explaining the RC dependence on the metal contact materials employed in this work and on the applied back\u2013gate voltage. In this respect, the M\u2013G distance is paramount in determining the RC behavior

The interpretation of commutative justice theory in the realm of contracts

Commutative justice, in the philosophy of law, means giving the exact amount of everybodyâs rights and achieves without interference, and distributive justice is concerned to distribution of property by state. Commutative justice theory, from a more practical perspective, means the necessity of balancing the partiesâ rights in bilateral contracts and if it is blemished, it should be compensated by other legal principles. In Iranâs law, this theory is justified by arguments like rule of âwaste of the object of sale before its receiptâ and legal options. Whereas this theory is rejected, balancing the partiesâ rights in bilateral contract will be broken

Fuzzy-Data Envelopment Analysis approach to Enterprise Resource Planning system analysis and selection

Nowadays, companies have invested considerable resources in the implementation of Enterprise Resource Planning (ERP) systems. As a comprehensive software solution, ERP seeks to integrate all departments and functions of a company into a single computer system that can satisfy all departments' information needs. Many companies have wasted millions of dollars as a consequence of failed ERP implementation and adoption. Some of these failures come back to the selection of an ineffective ERP system. This article seeks to propose a method for selecting appropriate ERP systems, to enable firms' decision-makers to achieve an overall consensus by using a decision support process. In addition, since estimating distinct and precise data in the field of Information Systems is hard, a Fuzzy-Data Envelopment Analysis model is used to evaluate the value of each ERP software solution using subjective judgments made by a group of high prestigious IT experts in the petrochemical industry.No Full Tex

An integrated framework for supplier evaluation and order allocation in a non-crisp environment

Supplier selection and related issues are among the most important decisions in the area of Supply Chain Management. A few of papers and studies have considered the major decisions related to supplier selection with non-crisp data. This paper comes across with a novel approach to the problem by presenting an integrated framework which involves two stages: suppliers’ evaluation and order allocation. In this way, for suppliers’ evaluation, a Fuzzy Data Envelopment Analysis (Fuzzy DEA) model is conducted and then a multi-objective integer programming with fuzzy objectives and fuzzy constraints is formulated to assign an optimal quantity of orders to suppliers

Negative capacitance field-effect transistor based on a two-dimensional ferroelectric

Negative capacitance field effect transistors (NCFETs) based on ferroelectric materials have been the focus of intensive research activities because of their relatively small sub-Threshold swing. This work proposes and presents a comprehensive study of a NCFET based on few-layer alpha-In2 Se3 as the ferroelectric in order to reduce the sub-Threshold swing through voltage amplification effect. By employing first principles electronic structure calculations, the Landau constants of mono and few-layer alpha-In2 Se3 are extracted which were utilized for analyzing the characteristics of a NCFET with a monolayer MoS2 as the channel material. Sub-Threshold swings in the range of sim 27-59 mV/dec were achieved for few-layer alpha-In2 Se3 that can be further improved by increasing the thickness of the ferroelectric layer and by using a thinner or high-kappa insulate layer

Understanding the influence of HEPES buffer concentration on the biodegradation of pure magnesium: an electrochemical study

A systematic electrochemical study was performed to understand the influence of HEPES buffer concentration on the biodegradation behaviour of pure magnesium in a pseudo-physiological solution (Earle's balanced salt solution (EBSS)). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation experiments suggest that HEPES accelerates the degradation of magnesium. While 5% CO2 in EBSS reduced the polarisation resistance (R-p) of magnesium by similar to 79%, addition of HEPES (25 mM) to EBSS decreased the R-p of magnesium by similar to 98% and escalated the corrosion current (i(corr)) by over an order of magnitude as compared to that in EBSS. Increase in HEPES concentration (50 mM and 100 mM) further increased the degradation of magnesium. Interestingly, the bulk pH difference between EBSS + HEPES and EBSS + CO2, before and after the electrochemical testing, was only marginal. However, the polarisation curves and Fourier transform infrared (FTIR) spectroscopy analysis suggest that HEPES affected the formation of insoluble salt layer (phosphate and carbonate) on the surface of magnesium. This effect can be attributed to the increase in the ionic strength of the solution due to HEPES addition