Families with cancer experiences changed five cancer risk behaviors when approached in Primary Care with interventions based on social cognitive models.

Silicene is a two-dimensional buckled material with broken horizontal mirror symmetry and Dirac-like dispersion. Under such conditions, flexural acoustic (ZA) phonons play a dominant role. Consequently, it is necessary to consider some suppression mechanism for electron-phonon interactions with long wavelengths in order to reach mobilities useful for electronic applications.In this work, we analyze, by means of an ensemble Monte Carlo simulator, the influence of several possibilities for the description of the effect of ZA phonon damping on electronic transport in silicene. The results show that a hard cutoff situation (total suppression for phonons with a wavelength longer than a critical one), as it has been proposed in the literature, does not yield a realistic picture regarding the electronic distribution function, and it artificially induces a negative differential resistance at moderate and high fields. Sub-parabolic dispersions, on the other hand, may provide a more realistic description in terms of the behavior of the electron distribution in the momentum space, but need extremely short cutoff wavelengths to reach functional mobility and drift velocity values.

We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared to considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between 1 and 3 × 10 12 cm −2 . Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carrier cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density. * Electronic mail: raulr@usal.es; Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Appl. Phys. Lett. 108, 043105 (2016) and may be found at http://dx. Graphene features, among other properties, large carrier mobility at room temperature along with gapless linear energy spectra for electrons and holes, that results in a linear optical absorption with virtually no photon wavelength restriction,[1] making it a promising material for the development of a wide range of highly efficient photonic and optoelectronic applications, including those operating in the terahertz range. [2-4] Consequently, an intense effort has been made in the recent years in order to get a good understanding of the carrier dynamics involved during and after photoexcitation [5][6][7][8][9][10][11][12][13][14] from a purely theoretical approach and also from an experimental point of view (pump-probe differential transmission spectroscopy) accompanied by means of various modelling techniques. Right after photoexcitation, an ultrafast thermalization of the carriers takes place driven by Coulomb dual carrier scattering. [13,15,16] Simultaneosly, the carriers partially cool by transferring their energy to the graphene and substrate lattices by means of phonon cascade emissions. [5,8,11,16] As a result, a hot thermal distribution of electrons and holes is achieved in tens of fs. [7,8,10] Later processes involve the cooling of the carriers as a consequence of scattering with phonons in the tail of the energy distribution, at the same time that recombination leads the system towards the full thermodynamic equilibrium. [5,11] Several authors remark the importance that the hot phonon (HP) effect would have on this dynamics. [6,7,17] The ensemble Monte Carlo (EMC) technique has been employed to study the influence of HP on the static transport properties of monolayer graphene under high-field conditions. [18] This method has been proven also to be worthy in the study of ultrafast carrier dynamics in a sub-ps time scale in other m...

Hexagonal boron nitride (h-BN) encapsulation significantly improves carrier transport in graphene. This work investigates the benefit of implementing the encapsulation technique in graphene field-effect transistors (GFET) in terms of their intrinsic radio frequency (RF) performance, adding the effect of the series resistances at the terminals. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity are obtained by an ensemble Monte Carlo simulator upon considering the relevant scattering mechanisms that affect carrier transport. RF figures of merit are simulated using an accurate small-signal model. Results reveal that the cutoff frequency could scale up to the physical limit given by the inverse of the transit time. Projected maximum oscillation frequencies, in the order of few THz, are expected to exceed the values demonstrated by InP and Si based RF transistors.The existing trade-off between power gain and stability and the role played by the gate resistance are also studied. High power gain and stability are feasible even if the device is operated far away from current saturation. Finally, the benefits of device unilateralization and the exploitation of the negative differential resistance region to get negative-resistance gain are discussed. Index Termsh-BN encapsulated graphene, graphene field-effect transistors, negative differential resistance, radio frequency, stability ACKNOWLEDGMENT Authors would like to thank Prof. Francisco García Ruiz for the helpful discussions.

The quality of graphene in nanodevices has increased hugely thanks to the use of hexagonal boron nitride as a supporting layer. This paper studies to which extent hBN together with channel length scaling can be exploited in graphene field-effect transistors (GFETs) to get a competitive radio-frequency (RF) performance. Carrier mobility and saturation velocity were obtained from an ensemble Monte Carlo simulator that accounted for the relevant scattering mechanisms (intrinsic phonons, scattering with impurities and defects, etc.). This information is fed into a self-consistent simulator, which solves the driftdiffusion equation coupled with the two-dimensional Poisson's equation to take full account of short channel effects. Simulated GFET characteristics were benchmarked against experimental data from our fabricated devices. Our simulations show that Manuscript 2 scalability is supposed to bring to RF performance an improvement that is, however, highly limited by instability. Despite the possibility of a lower performance, a careful choice of the bias point can avoid instability. Nevertheless, maximum oscillation frequencies are still achievable in the THz region for channel lengths of a few hundreds of nanometers.