Scalable Patterning of Encapsulated Black Phosphorus

Abstract

Atomically thin black phosphorus (BP) has attracted considerable interest due to its unique properties, such as an infrared band gap that depends on the number of layers and excellent electronic transport characteristics. This material is known to be sensitive to light and oxygen and degrades in air unless protected with an encapsulation barrier, limiting its exploitation in electrical devices. We present a new scalable technique for nanopatterning few layered BP by direct electron beam exposure of encapsulated crystals, achieving a spatial resolution down to 6 nm. By encapsulating the BP with single layer graphene or hexagonal boron nitride (hBN), we show that a focused electron probe can be used to produce controllable local oxidation of BP through nanometre size defects created in the encapsulation layer by the electron impact. We have tested the approach in the scanning transmission electron microscope (STEM) and using industry standard electron beam lithography (EBL). Etched regions of the BP are stabilized by a thin passivation layer and demonstrate typical insulating behavior as measured at 300 and 4.3 K. This new scalable approach to nanopatterning of thin air sensitive crystals has the potential to facilitate their wider use for a variety of sensing and electronics applications.

Remarkable Reduction of Interfacial Thermal Resistance in Nanophononic Heterostructures

“…It is worth noting that such phononic crystal structures can be realized experimentally. The scalable technique for patterning few-layer BP via direct electron beam exposure was presented by Nick Clark et al [53] In their work, a spatial resolution down to 6 nm was realized. Besides, Liu et al synthesized holey phosphorene by electrochemical method with the pore size ranges from a few nanometers to tens of nanometers.…”

Enhanced Superconductivity in Few-Layer TaS2 due to Healing by Oxygenation

“…Therefore, to minimise degradation, the crystals were mechanically exfoliated from bulk TaS 2 in the inert atmosphere of a glovebox and encapsulated with monolayer graphene following the procedure reported in ref. 36. The encapsulation is known to provide reliable protection from moisture and oxygen in ambient conditions as long as the resulting graphene-TMD-graphene (or hBN-TMD-hBN) stack exhibits so-called self-cleaning, 37,38 i.e., strong adhesion between atomically thin crystals squeezes out adsorbed water and hydrocarbons into sub-micrometer-size pockets (bubbles), leaving the remaining interfaces atomically sharp and largely free of contaminants.…”

Recent Advances in Chemical Functionalization of 2D Black Phosphorous Nanosheets

“…To this end, continuous efforts have been devoted from researchers to overcome the poor ambient stability of BPNSs and various techniques such as Al 2 O 3 protective layer coating, h ‐BN encapsulation, hybrid Al 2 O 3 /BN encapsulation, ionophore coating, and chemical modification, have been demonstrated. For example, Al 2 O 3 protection can preserve the properties of BPNSs over 7 d of ambient exposure, however, a long‐term stability is still challenging.…”