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A transimpedance amplifier for ultralow current scanning tunneling microscopy has been developed. Conditions for maximum signal-to-noise ratio have been explored, showing that best results can be obtained with a simple circuital arrangement. The amplifier associates a very high amplification factor (0.5 V/pA) to a sufficiently wide bandwith (1.6 kHz) and very low noise current (49 fA). Those features enable microscopy studies on an almost insulating surface, such as a freshly cleaved mica surface.

We report on scanning tunneling microscopy and spectroscopy (STM/STS) investigations of graphene grown on a 6H-SiC(0001) substrate. Our STM images of a graphene layer on a step bunching of the SiC feature a (√3 × √3)R30° pattern of aromatic rings and well developed, sharp Van Hove singularities in the corresponding STS spectra. High-resolution STM images show that the flake is discontinuous at the step edge. Simulations based on density functional theory indicate that the graphene edge is terminated armchair.

We have developed metal-oxide graphene field-effect transistors (MOGFETs) on sapphire substrates working at microwave frequencies. For monolayers, we obtain a transit frequency up to ~ 80 GHz for a gate length of 200 nm, and a power gain maximum frequency of about ~ 3 GHz for this specific sample. Given the strongly reduced charge noise for nanostructures on sapphire, the high stability and high performance of this material at low temperature, our MOGFETs on sapphire are well suited for a cryogenic broadband low-noise amplifier.

We report on the preparation of carbon nanotube quantum dots using superconducting electrodes made of niobium. Gate-controllable supercurrents with values of up to 30 nA are induced by the proximity effect. The IV-curves are hysteretic at low temperature and the corresponding switching histograms have a width of ~0.5-2. An on-chip resistive environment integrated in the sample layout is used in order to increase the switching current.