Electronic 1/fNoise in h-BN-Graphene-h-BN and High Breakdown Current Density in h-BN-TaSe3 van der Waals Heterostructures
In the first part of the manuscript we have investigated low-frequency 1/f noise in the boron nitride – graphene – boron nitride heterostructure field-effect transistors on Si/SiO2 substrates (f is a frequency). The device channel was implemented with a single layer graphene encased between two layers of hexagonal boron nitride. The transistors had the charge carrier mobility in the range from ~30000 to ~36000 cm2/Vs at room temperature. It was established that the noise spectral density normalized to the channel area in such devices can be suppressed to ~510-9 μm2 Hz-1 , which is a factor of 5 – 10 lower than that in non-encapsulated graphene devices on Si/SiO2. The physical mechanism of noise suppression was attributed to screening of the charge carriers in the channel from traps in SiO2 gate dielectric and surface defects. The obtained results are important for the electronic and optoelectronic applications of graphene.
In the second part of this work we report on the current-carrying capacity of the nanowires made from the quasi-1D van der Waals metal tantalum triselenide capped with quasi-2D boron nitride. The chemical vapor transport method followed by chemical and mechanical exfoliation was used to fabricate the mm-long TaSe3 wires with the lateral dimensions in the 20 to 70 nm range. Electrical measurements establish that the TaSe3/h-BN nanowire heterostructures have a breakdown current density exceeding 10 MA/cm2 — an order-of-magnitude higher than that for copper. Some devices exhibited an intriguing step-like breakdown, which can be explained by the atomic thread bundle structure of the nanowires. The quasi-1D single crystal nature of TaSe3 results in a low surface roughness and in the absence of the grain boundaries. These features can potentially enable the downscaling of the nanowires to the lateral dimensions in a few-nm range. Our results suggest that quasi-1D van der Waals metals have potential for applications in the ultimately downscaled local interconnects.