Single-Particle Tunneling in Doped Graphene-Insulator-Graphene Junctions

The characteristics of tunnel junctions formed between n- and p-doped graphene are investigated theoretically. The single-particle tunnel current that flows between the two-dimensional electronic states of the graphene (2D-2D tunneling) is evaluated. At a voltage bias such that the Dirac points of the two electrodes are aligned, a large resonant current peak is produced. The magnitude and width of this peak is computed, and its use for devices is discussed. The influence of both rotational alignment of the graphene electrodes and structural perfection of the graphene is discussed.Comment: 23 pages, 9 figures; added Section II(E) and associated figures, and made other minor typographical correction

Inelastic Effects in Low-Energy Electron Reflectivity of Two-dimensional Materials

A simple method is proposed for inclusion of inelastic effects (electron absorption) in computations of low-energy electron reflectivity (LEER) spectra. The theoretical spectra are formulated by matching of electron wavefunctions obtained from first-principles computations in a repeated vacuum-slab-vacuum geometry. Inelastic effects are included by allowing these states to decay in time in accordance with an imaginary term in the potential of the slab, and by mixing of the slab states in accordance with the same type of distribution as occurs in a free-electron model. LEER spectra are computed for various two-dimensional materials, including free-standing multilayer graphene, graphene on copper substrates, and hexagonal boron nitride (h-BN) on cobalt substrates.Comment: 21 pages, 7 figure

SymFET: A Proposed Symmetric Graphene Tunneling Field Effect Transistor

In this work, an analytical model to calculate the channel potential and current-voltage characteristics in a Symmetric tunneling Field-Effect-Transistor (SymFET) is presented. The current in a SymFET flows by tunneling from an n-type graphene layer to a p-type graphene layer. A large current peak occurs when the Dirac points are aligned at a particular drain-to- source bias VDS . Our model shows that the current of the SymFET is very weakly dependent on temperature. The resonant current peak is controlled by chemical doping and applied gate bias. The on/off ratio increases with graphene coherence length and doping. The symmetric resonant peak is a good candidate for high-speed analog applications, and can enable digital logic similar to the BiSFET. Our analytical model also offers the benefit of permitting simple analysis of features such as the full-width-at-half-maximum (FWHM) of the resonant peak and higher order harmonics of the nonlinear current. The SymFET takes advantage of the perfect symmetry of the bandstructure of 2D graphene, a feature that is not present in conventional semiconductors

De Impact van Smartphone Gebruik na het Werk op Herstelactiviteiten en Ervaren Herstel en de rol van Psychologisch Detachment als Mediator

Door nieuwe communicatiemiddelen zoals de smartphone zijn medewerkers 24/7 bereikbaar. Smartphones worden meestal gebruik voor e-mails en internet. Werkgevers zien de voordelen in van smartphone’s en verschaffen werknemers een werktelefoon. In ruil daarvoor willen werkgevers snel antwoord op berichten, ook in de vrije tijd. Medewerkers herstellen meestal tijdens de avonduren van het werk. Volgens de effort-recovery theory (Meijman & Meijman, 1998) herstelt men door ondernomen activiteiten, gebruik makend van andere bronnen dan die van tijdens het werk en door psychologisch afstand nemen. Verstoort smartphone gebruik dit proces? Het doel van dit onderzoek is in de eerste plaats na te gaan wat de impact van smartphone gebruik is op herstelactiviteiten en ervaren herstel. Ten tweede doel is nagaan of psychologisch detachment een mediator is in de relatie tussen herstelactiviteiten en ervaren herstel

Path distributions for describing eigenstates of the harmonic oscillator and other 1-dimensional problems

The manner in which probability amplitudes of paths sum up to form wave functions of a harmonic oscillator, as well as other, simple 1-dimensional problems, is described. Using known, closed-form, path-based propagators for each problem, an integral expression is written that describes the wave function. This expression conventionally takes the form of an integral over initial locations of a particle, but it is re-expressed here in terms of a characteristic momentum associated with motion between the endpoints of a path. In this manner, the resulting expression can be analyzed using a generalization of stationary-phase analysis, leading to distributions of paths that exactly describe each eigenstate. These distributions are valid for all travel times, but when evaluated for long times they turn out to be real, non-negative functions of the characteristic momentum. For the harmonic oscillator in particular, a somewhat broad distribution is found, peaked at value of momentum that corresponds to a classical energy which in turn equals the energy eigenvalue for the state being described.Comment: 26 page, 10 figures; in v2, added refs. 43 and 44 along with a brief description of the latter, and made a few minor typographical correction