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Lattice defects and dielectric environment play a crucial role for 2D materials. Gas molecules can get physisorbed easily on the surface through van der Waals forces and can modify dramatically their electronic and optical properties. In this work, we investigate the impact of the physisorbed gas molecules on the optical properties of MoSe2 monolayers by means of low-temperature photoluminescence (PL). More specifically, we focus on the physics of excitons localized by gas molecules. The associated PL peak is observed to show a systematic and large red-shift with temperature and a blue-shift with laser irradiation. Both energy shifts are explained in terms of thermal instability of the localization in combination with hopping effects. Finally, a model is presented, which can reproduce the experimental data with excellent agreement.

We present measurements on nanomechanical resonators allowing full in situ tuning of their dynamic properties, including higher-order nonlinearities (up to fifth order) and the mechanical quality factor Q. This is accomplished by gating electrodes and balancing resonators, similarily to a classical tuning fork. A detailed modal analysis is performed and reproducibility of the device response is verified. Eigenfrequencies are in the range of 40 to 70 MHz, and quality factor rises up to Q∼6×103.

The application of a non-destructive method for characterization of electronic structure of an ultra-thin SnO1

Nanomechanical resonators, of importance for signal filtering and transduction, are investigated within the limit of extreme nonlinear excitation. The Ruelle–Takens route establishes the transition of a system into chaos with n frequencies present. By providing a set of three sources, this transition from linear to nonlinear and finally to chaotic response can be traced, and it is found in our experiment. Knowledge of potentially chaotic behavior of nanomechanical systems is crucial for their application. Our resonator system has an overall length of 4 μm and a cross section of about 100 nm×300 nm with natural frequencies of ∼50 MHz.

We present measurements on nanoelectromechanical systems fabricated in semiconductor materials suited for operating frequencies in the radio band. We demonstrate how to achieve parametric frequency tuning of nanoelectromechanical resonators required for radio frequency sensor and communication applications.

We report on a nanomachined electromechanical resonator applied as a mechanically flexible tunneling contact. The resonator was machined out of a single-crystal silicon-on-insulator substrate and operates at room temperature with frequencies up to some 73 MHz, transferring electrons by mechanical motion.

Whispering gallery modes (WGMs) excited by the intrinsic photoluminescence (PL) in zinc oxide microspherical resonators are investigated in this work. The microspheres were synthesized via a one-pot hydrothermal technique. A polymer was applied after the synthesis to fill remaining pores in the oxide particle. Defect-related ZnO PL was excited in the visible, coupling to WGMs. The observed WGMs red-shift with increasing refractive index of the surrounding medium with a sensitivity of 90–100 nm/refractive index unit. The spherical microresonators may be used to investigate binding to and structure at the particle/solution interface.

We report on the coupling of spin vortices in magnetic multilayer elements. The magnetization distribution in thin film disks consisting of two ferromagnetic layers separated by a nonmagnetic spacer is imaged layer resolved by using x ray microscopy. We directly observe two fundamentally different vortex coupling states namely antiferromagnetic and ferromagnetic orientation of the flux directions. It is found that these states are predetermined for systems that involve a sufficiently strong interlayer exchange coupling whereas for the case of a purely dipolar interaction both states are transformable into each other. (C) 2011 American Institute of Physics. [doi:10.1063/1.3597297]

In this paper, the generation of a magnetic field-free line (FFL) along a constant direction is investigated. It is shown that an FFL gradient field can be generated by two perpendicular Maxwell coil pairs. These coils can be used for imaging distributions of superparamagnetic nanoparticles with high sensitivity applying the magnetic particle imaging technique. To this end, the FFL has to be rapidly moved back and forth while either the object or the coil assembly rotates slowly. The field quality of the proposed coil setup is assessed by manufacturing a prototype and measuring the magnetic field using a Hall-effect sensor.