Abstract
Black Phosphorus (BP) is an excellent material from the post graphene era due to its layer dependent band gap, high mobility and high Ion/Ioff. However, its poor stability in ambient poses a great challenge for its practical and long-term usage. The optical visualization of the oxidized BP is the key and the foremost step for its successful passivation from the ambience. Here, we have conducted a systematic study of the oxidation of the BP and developed a technique to optically identify the oxidation of the BP using Liquid Crystal (LC). It is interesting to note that we found that the rapid oxidation of the thin layers of the BP makes them disappear and can be envisaged by using the alignment of the LC. The molecular dynamics simulations also proved the preferential alignment of the LC on the oxidized BP. We believe that this simple technique will be effective in passivation efforts of the BP, and will enable it for exploitation of its properties in the field of electronics.
Highlights
The 2D layered materials, such as graphene and transition metal di-chalcogenides (TMDs), have opened a new era for electronic devices
The glass slide was placed on the sample so that the coated liquid crystal (LC) film and the Polyvinyl Alcohol (PVA) were in contact
When the sample was coated with the LC and observed under a polarized optical microscopy (POM), interestingly we found remnants of a completely oxidized Black Phosphorus (BP) at a point which is indicated as Pt. 1 in Fig. 2b, which was invisible otherwise
Summary
Bilal Abbas Naqvi 1,2, Muhammad Arslan Shehzad[1,2,4], Janghwan Cha[2,3], Kyung-Ah Min[2,3], M. The surface of the relatively thin BP flakes, which are the most suitable candidates for electronic devices, get oxidized within an hour after cleavage from bulk if exposed to an ambient environment[1,8] This oxidation causes irreparable damages to the physical characteristic of the BP9–11. The nematic phase of the LC gained a lot of significance after its alignment has been studied on synthetically grown 2D materials, such as graphene, hBN and TMDs, for the optical visualization of their grains[19,24,25]. This birefringent behaviour in the LC makes it a suitable option to study the anisotropy as well as the surface defects.
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