A bimodal magnetic force microscopy (MFM) that uses an external magnetic field for the detection and imaging of magnetic thin films is developed. By applying the external modulation magnetic field, the vibration of a cantilever probe is excited by its magnetic tip at its higher eigenmode. Using magnetic nanoparticle samples, the capacity of the technique which allows single-pass imaging of topography and magnetic forces is demonstrated. For the detection of magnetic properties of thin film materials, its signal-to-noise ratio and sensitivity are demonstrated to be superior to conventional MFM in lift mode. The secondary resonance MFM technique provides a promising tool for the characterization of nanoscale magnetic properties of various materials, especially of magnetic thin films with weak magnetism.
The response behavior of artificially tilted multilayer thermoelectric devices (ATMTDs) to thermal radiation has been intensely investigated for remote thermal detection; however, their response behavior to thermal contact is still not well understood. In this letter, Fe/Bi2Te2.7Se0.3 ATMTDs have been fabricated by alternately stacking metallic Fe layers and Bi2Te2.7Se0.3 layers to reveal the response behavior to thermal contact. It was found that the transverse thermoelectric voltages (ΔVx) of the ATMTDs once contacting heat source were rapidly raised in the first seconds and then nonlinearly attenuated after reaching maximum ΔVx. A one-dimensional unsteady heat transfer model was proposed to reveal the attenuation process, which obeys an exponential variation and strongly depends on the heat source temperature. Using the ATMTDs as temperature sensors, the detection uncertainty can be less than 1 K. This work has demonstrated great potential application of the ATMTDs in the field of contact-type temperature detection.
Given the stray capacitance between the probe and sample surface, electrostatic force microscopy (EFM) suffers from the probe averaging effect of electrostatic signals for measuring nanoscale potential distributions. A method for reconstructing an EFM image is presented by using the step response function (SRF) as the system transfer function. The SRF is constructed numerically by conducting finite element method simulations and reconsidering both the probe shape and tip-sample distance. The deconvolution of the probe averaging effect for the electrostatic image is demonstrated using an elaborated sample of graphene ribbons that are used as nanoscale surface potential steps. The lateral resolution of the electrostatic image is improved via deconvolution. The results present a powerful tool for explaining the EFM image to reduce the probe averaging effect effectively, especially for the sample with nanoscale potential steps.
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