High-resolution mapping of infraslow cortical brain activity enabled by graphene microtransistors. Nature Materials, (2019). 18.

We present an investigation of large, isolated, graphene ribbons grown on the C-face of on-axis semi-insulating 6H-SiC wafers. Using a graphite cap to cover the SiC sample, we modify the desorption of the Si species during the Si sublimation process. This results in a better control of the growth kinetics, yielding very long (about 300 µm long, 5 µm wide), homogeneous monolayer graphene ribbons. These ribbons fully occupy unusually large terraces on the step bunched SiC surface, as shown by AFM, optical microscopy and SEM. Raman spectrometry indicates that the thermal stress has been 1

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We present a time-resolved study of the evaporation in air of minuscule sessile droplets deposited by nanodispensing techniques. Highly sensitive nanomechanical resonators are designed to monitor in time the mass variation of evaporating liquid droplets. The precision of the measurement setup enables the study of droplets with diameters in the 1 mum range, which correspond to volumes of femtoliters and smaller, 9 orders of magnitude smaller than most of presently published data. Experimental data are compared with macroscopic models.

An investigation of the early stage formation of graphene on the C-face of 6H-silicon carbide (SiC) is presented. We show that the sublimation of few atomic layers of Si out of the SiC substrate is not homogeneous. In good agreement with the results of theoretical calculations it starts from defective sites, mainly dislocations that define nearly circular graphene layers, which have a pyramidal, volcano-like, shape with a center chimney where the original defect was located. At higher temperatures, complete conversion occurs but, again, it is not homogeneous. Within the sample surface, the intensity of the Raman bands, evidences non-homogeneous thickness.

Owing to their low dark current, high transparency, high thermal conductivity, and potential radiation hardness, there is a special interest in silicon carbide (SiC) devices for radiation monitoring in radiation harsh environments and with elevated temperatures and, especially, for the plasma diagnostic systems in future nuclear fusion reactors. In this work, four-quadrant p-n junction diodes produced on epitaxial 4H-SiC substrates are studied. The impact of electron, neutron, and proton irradiations (up to fluences of 1 × 10 16 electrons (e)/cm 2 , 2 × 10 15 neutrons (n)/cm 2 , and 2.5 × 10 15 protons (p)/cm 2 , respectively) on the electrical characteristics is studied by means of current-voltage (I-V) and capacitance-voltage (C-V) techniques. Regardless of the particle type and applied fluences, the results show similar low reverse currents for irradiated SiC devices, which are at least about four orders of magnitude lower than comparable Si devices. The effects of irradiation on interquadrant resistance and charge build-up in the interquadrant isolation are assessed. Furthermore, device performance as a radiation detector is investigated upon exposure to a collimated 239 Pu-241 Am-244 Cm trialpha source. The performance at room temperature is preserved even for the highest irradiation fluences, despite the fact that the rectification character in electrical characteristics is lost. From the results, advantages of using SiC devices in alpha particle detection in harsh environments can be envisaged.

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A new technique for producing nanometre scale patterns on thin layers (<30 nm thick) of PMMA on silicon is described. The method consists of inducing the local modification of the PMMA by applying a positive voltage between the silicon and an atomic force microscope (AFM) tip. At voltages larger than 28 V, it is observed that a hole is directly produced on the PMMA. The silicon surface is simultaneously oxidized even in the case where a hole has not been created. Monitoring of the electrical current through the AFM tip during the application of the voltage allows elucidating the mechanism of the PMMA removal. The process is used to define nanometre scale electrodes by combining the AFM lithography with electron beam lithography, metal deposition and lift-off processes.