The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene–metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored. Here we have investigated the contact noise in graphene field-effect transistors of varying device geometry and contact configuration, with carrier mobility ranging from 5,000 to 80,000 cm2 V−1 s−1. Our phenomenological model for contact noise because of current crowding in purely two-dimensional conductors confirms that the contacts dominate the measured resistance noise in all graphene field-effect transistors in the two-probe or invasive four-probe configurations, and surprisingly, also in nearly noninvasive four-probe (Hall bar) configuration in the high-mobility devices. The microscopic origin of contact noise is directly linked to the fluctuating electrostatic environment of the metal–channel interface, which could be generic to two-dimensional material-based electronic devices.

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We report on the results of a systematic series of experiments aimed at improving the stability of amorphous silicon (a-Si:H) films. We find that very low levels (0.2–0.4 ppm) of compensation by boron, when combined with growth conditions that favor a robust microstructure in the material, results in films with significantly improved stability and very low defect density. The films were grown using a reactive plasma beam technique using a remote plasma beam from an electron-cyclotron-resonance source. The improvement in stability is seen under both short-term (a few minutes) light soaking, and also under light soaking under high intensity (10×sun) illumination conditions. We conclude that the improvement in initial stability is a result of compensation of native donors (probably oxygen) in the material by boron. The surprising reduction in long term instability and corresponding defect density upon compensation implies that the microstructure and structural changes around the native impurities may play a role in the long-term instability of the material.

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The authors report a detailed investigation of the flicker noise (1/f noise) in graphene films obtained from chemical vapour deposition (CVD) and chemical reduction of graphene oxide. The authors find that in the case of polycrystalline graphene films grown by CVD, the grain boundaries and other structural defects are the dominant source of noise by acting as charged trap centres resulting in huge increase in noise as compared with that of exfoliated graphene. A study of the kinetics of defects in hydrazine-reduced graphene oxide (RGO) films as a function of the extent of reduction showed that for longer hydrazine treatment time strong localised crystal defects are introduced in RGO, whereas the RGO with shorter hydrazine treatment showed the presence of large number of mobile defects leading to higher noise amplitude.