Theory of thermionic emission from a two-dimensional conductor and its application to a graphene-semiconductor Schottky junction

The standard theory of thermionic emission developed for three-dimensional semiconductors does not apply to two-dimensional materials even for making qualitative predictions because of the vanishing out-of-plane quasiparticle velocity. This study reveals the fundamental origin of the out-of-plane charge carrier motion in a two-dimensional conductor due to the finite quasiparticle lifetime and huge uncertainty of the out-of-plane momentum. The theory is applied to a Schottky junction between graphene and a bulk semiconductor to derive a thermionic constant, which, in contrast to the conventional Richardson constant, is determined by the Schottky barrier height and Fermi level in graphene.Comment: 4+ pages, 3 figs, 60 refs, a somewhat compressed version has been published in AP

Minimum Electrical and Thermal Conductivity of Graphene: A Quasiclassical Approach

We investigate the minimum conductivity of graphene within a quasiclassical approach taking into account electron-hole coherence effects which stem from the chiral nature of low energy excitations. Relying on an analytical solution of the kinetic equation in the electron-hole coherent and incoherent cases we study both the electrical and thermal conductivity whose relation fullfills Wiedemann-Franz law. We found that the most of the previous findings based on the Boltzmann equation are restricted to only high mobility samples where electron-hole coherence effects are not sufficient.Comment: 4 pages 1 figure (final version, as published in PRL

Pseudospin in optical and transport properties of graphene

We show that the pseudospin being an additional degree of freedom for carriers in graphene can be efficiently controlled by means of the electron-electron interactions which, in turn, can be manipulated by changing the substrate. In particular, an out-of-plane pseudospin component can occur leading to a zero-field Hall current as well as to polarization-sensitive interband optical absorption.Comment: 4 pages, 2 figure

Theory of photoexcited and thermionic emission across a two-dimensional graphene-semiconductor Schottky junction

This paper is devoted to photocarrier transport across a two-dimensional graphene-semiconductor Schottky junction. We study linear response to monochromatic light with excitation energy well below the semiconductor band gap. The operation mechanism relies on both photoelectric and thermionic emission from graphene to a two-dimensional semiconductor under continuous illumination and zero bias. Due to the thermalization bottleneck for low-energy carriers in graphene, the photoelectric contribution is found to dominate the photoresponse at near-infrared excitation frequencies and below. The extended thermalization time provides an interesting opportunity to facilitate the interlayer photocarrier transport bypassing the thermalization stage. As a result, the total photoresponsivity rapidly increases with excitation wavelength making graphene-semiconductor junctions attractive for photodetection at the telecommunication frequency.Comment: 6+ pages, 3 figures update

The hope for neglected diseases: R&D incentives

Neglected diseases are neglected because they cannot generate enough return on R&D to pharmaceutical firms. This paper analyzes and compares existing proposals for public intervention in R&D for neglected diseases. Incentives for neglected diseases are comprehensively evaluated based on seventeen selected criteria grouped into four categories: efficiency, feasibility, fairness, and sustainability. Our conclusion is that public-private partnerships coordinated through a centralized service platform have the highest potential to satisfy the criteria for the successful development..neglected diseases, incentives, pharmaceutical R&D, policy analysis

Two-stage public-private partnership proposal for R&D on neglected diseases

We propose a 2-stage procurement model of public-private partnership to provide better incentives for R&D on neglected diseases. The model combines advance market commitment, subsidized clinical trials, and rewards based on therapeutical contributions of new drugs through a prize screening mechanism. The model is primarily intended to facilitate small firms’ R&D by providing cash flow, rewarding quality of new drugs, and sharing risks and costs of new drugs development, while limiting moral hazards. The model’s advantages include reduction of overpayments, better disclosure of information, provision of production licences, and direct targeting of better quality drugs.neglected diseases, prize screening, pharmaceutical R&D