Quantitative measurement of the charge carrier concentration using dielectric force microscopy

The charge carrier concentration profile is a critical factor that determines semiconducting material properties and device performance.Dielectric force microscopy(DFM)has been previously developed to map charge carrier concentrations with nanometer-scale spatial resolution.However,it is challenging to quantitatively obtain the charge carrier concentration,since the dielectric force is also affected by the mobility.Here,we quantitative measured the charge carrier concentration at the saturation mobility regime via the rectification effect-dependent gating ratio of DFM.By measuring a series of n-type GaAs and GaN thin films with mobility in the saturation regime,we confirmed the decreased DFM-measured gating ratio with increasing electron concentration.Combined with numerical simulation to calibrate the tip–sample geometry-induced systematic error,the quantitative correlation between the DFM-measured gating ratio and the electron concentration has been established,where the extracted electron concentration presents high accuracy in the range of 4×10^(16)–1×10^(18)cm^(-3).We expect the quantitative DFM to find broad applications in characterizing the charge carrier transport properties of various semiconducting materials and devices.

Optical forces exerted on a graphene-coated dielectric particle by a focused Gaussian beam

In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.

A Comparison between Abraham and Minkowski Momenta

In this paper I compare the Abraham and the Minkowski forms for the momentum pertaining to an electromagnetic wave inside a dielectric or a magnetic material. The discussion is based on a careful treatment of the surface charges and currents and of the forces acting on them. While in the dielectric case the Abraham momentum is certainly more appealing from the physical point of view, for a magnetic material it suggests an interpretation in terms of magnetic charges and related magnetic currents. The Minkowski momentum for magnetic non conducting materials, on the contrary, has a natural interpretation in terms of an amperian model, in which the dynamics is determined by the Lorentz force acting on bulk and surface electric currents.

Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

Measured highly elevated gains of proton–boron(HB11) fusion(Picciotto et al., Phys. Rev. X 4, 031030(2014))confirmed the exceptional avalanche reaction process(Lalousis et al., Laser Part. Beams 32, 409(2014); Hora et al.,Laser Part. Beams 33, 607(2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh acceleration above 10^(20) cm s^(-2)for plasma blocks was theoretically and numerically predicted since 1978(Hora, Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured(Sauerbrey, Phys. Plasmas 3, 4712(1996)) in exact agreement(Hora et al., Phys. Plasmas 14, 072701(2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell's stress tensor by the dielectric properties of plasma leading to the nonlinear(ponderomotive) force f_(NL)resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. This is supported also by other experiments with very high HB11 reactions under different conditions(Labaune et al., Nature Commun.4, 2506(2013)).