We investigate tunneling in metal-insulator-metal junctions employing few atomic layers of hexagonal boron nitride (hBN) as the insulating barrier. While the low-bias tunnel resistance increases nearly exponentially with barrier thickness, subtle fea
tures are seen in the current-voltage curves, indicating marked influence of the intrinsic defects present in the hBN insulator on the tunneling transport. In particular, single electron charging events are observed, which are more evident in thicker-barrier devices where direct tunneling is substantially low. Furthermore, we find that annealing the devices modifies the defect states and hence the tunneling signatures.
The electronic transport properties of single layer graphene having a dilute coating of indium adatoms has been investigated. Our studies establish that isolated indium atoms donate electrons to graphene and become a source of charged impurity scatte
ring, affecting the conductivity as well as magnetotransport properties of the pristine graphene. Notably, a positive magnetoresistance is observed over a wide density range after In doping. The low field magnetoresistance carries signatures of quantum interference effects which are significantly altered by the adatoms.
We experimentally address the importance of tuning in athermal phase transitions, which are triggered only by a slowly varying external field acting as tuning parameter. Using higher order statistics of fluctuations, a singular critical instability i
s detected for the first time in spite of an apparent universal self-similar kinetics over a broad range of driving force. The results as well as the experimental technique are likely to be of significance to many slowly driven non-equilibrium systems from geophysics to material science which display avalanche dynamics.
