This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

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The electronic properties of graphene

Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

http://pubs.acs.org/doi/pdf/10.1021/cr1002326

Solar Water Splitting Cells

This review provides numerical and graphical information about many (but by no means all) of the physical and electronic properties of GaAs that are useful to those engaged in experimental research and development on this material. The emphasis is on properties of GaAs itself, and the host of effects associated with the presence of specific impurities and defects is excluded from coverage. The geometry of the sphalerite lattice and of the first Brillouin zone of reciprocal space are used to pave the way for material concerning elastic moduli, speeds of sound, and phonon dispersion curves. A section on thermal properties includes material on the phase diagram and liquidus curve, thermal expansion coefficient as a function of temperature, specific heat and equivalent Debye temperature behavior, and thermal conduction. The discussion of optical properties focusses on dispersion of the dielectric constant from low frequencies [κ0(300)=12.85] through the reststrahlen range to the intrinsic edge, and on the ass...

Semiconducting and other major properties of gallium arsenide

A broad review of recent research work on the preparation and the remarkable properties of intercalation compounds of graphite, covering a wide range of topics from the basic chemistry, physics and materials science to engineering applications.

Intercalation compounds of graphite

Climate change and fossil fuel depletion are the main reasons leading to hydrogen technology. There are many processes for hydrogen production from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen production methods is carried out. The process descriptions along with the technical and economic aspects of 14 different production methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochemical pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 production with costs in the range of 1.34–2.27 $/kg. Biological methods appear to be a promising pathway but further research studies are needed to improve their production rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources.

A comparative overview of hydrogen production processes

Photoelectrolysis of water in cells with TiO2 anodes

A method is developed for calculating the statistical properties and galvanomagnetic effects of $p$-type Ge and Si for weak magnetic fields. The calculations involving the use of the Boltzmann transport theory are applied to the warped energy surfaces which have been determined by the cyclotron resonance experiments. Expressions are developed for the hole densities, conductivity, effective masses, intrinsic carrier concentration, and Hall coefficient as a series expansion in terms of the anisotropy parameters of the warped surfaces. Results have been obtained for the assumption that the relaxation time $\ensuremath{\tau}=l{\ensuremath{\epsilon}}^{\ensuremath{-}\ensuremath{\lambda}}$, where $l$ is a constant, $\ensuremath{\epsilon}$ is the energy of the carriers and $\ensuremath{\lambda}$ is a parameter whose numerical value depends on the scattering processes. By using the results of the calculations and existing experimental data, a speculation is made concerning the possible change with temperature of the combined effective mass of holes in germanium and the corresponding change in the band structure.

Statistics and Galvanomagnetic Effects in Germanium and Silicon with Warped Energy Surfaces

Infrared Magnetoreflection in Bismuth. I. High Fields

The room temperature pulsed magnetic field infrared cyclotron resonance data of Keyes and co-workers in indium antimonide is interpreted using the k\ifmmode\cdot\else\textperiodcentered\fi{}p perturbation technique of Kane, which is extended to include the effects of a dc magnetic field. The energy levels are calculated for a carrier in a band in the presence of a magnetic field and which is interacting with neighboring bands. From the energy expression, the variation of the apparent effective mass with magnetic field is calculated. The theory is consistent with the room temperature measurements of Keyes et al., as well as with other cyclotron resonance results obtained at low temperatures.

J. G. Mavroides

Papers

Photoelectrolysis of water in cells with TiO2 anodes

Statistics and Galvanomagnetic Effects in Germanium and Silicon with Warped Energy Surfaces

Infrared Magnetoreflection in Bismuth. I. High Fields

Cyclotron Resonance in Indium Antimonide at High Magnetic Fields

Magnetoreflection studies on the band structure of bismuth-antimony alloys☆