Black phosphorous consists of individual layers that can be sequestered by exfoliation, in the same way to how graphene is obtained from graphite. The single layer of black phosphorous, called phosphorene, can be laid down onto oxidized-silicon substrate. Together with metal thin-film electrical contacts, the structure acquires the properties of a field-effect transistor (FET), with the silicon substrate being the (back) gate. In contrast to graphene, phosphorene has a finite bandgap, i.e. is a 2D semiconductor. At the same time, the charge-carrier mobility is high. This prompts for using this material in some high-frequency applications. However, phosphorene readily oxidizes in ambient atmosphere, making the devises unstable.
This project looks at different ways of making a protection to phosphorene, by e.g. encapsulating it in Parylene. Parylene is a well-known in industry material, which can be deposited at room temperature in a self-assembly manner. Parylene thus forms a conformal protection layer that is free from voids and pinholes. Our preliminary experiments have shown that phosphorene-in-Parylene FET’s are quite stable and allow for several cool-downs without significant change of their electrical parameters (see Figure).
Figure. The transfer characteristics of phosphorene-in-Parylene field-effect transistor at different temperatures. Note a quite unusual symmetric character of the curves.