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Photoluminescence Properties of Mechanically Exfoliated Bi2S3

  • Supervisor: Peter Schall
  • Project Type: Bachelor / Master Project
  • Goal: To learn about the fundamental photo-physical mechanism in this new class of materials
  • Info: Send an email to: P. Schall

Layered two-dimensional materials have strong in-plane bonding but weak out-of-plane bonding. This allows them to be peeled layer by layer, literally with regular household tape.

In recent years, the “mechanical exfoliation” of layered materials using scotch tape, as in graphite/graphene and MoS2, has yielded a novel class of 2D materials with exciting optical and electronic properties, and spurred the search for even further layered compounds. Among the many systems investigated are the transition metal dichalcogenides, transition metal tri-chalcogenides and post-transition metal trichalcogenide semiconductors. Belonging to this last group is Bi2S3, a direct-bandgap (`~1.4 eV) semiconductor showing photolumi-nescence in the visible region in nanocrystal form as prepared by solution-phase methods. However, no reports have been made yet on direct mechanical exfoliation of this compound and the resulting optical properties. In this project, we attempt to mechanically exfoliate bulk Bi2S3 and characterize its optical properties. In addition, early reports on liquid exfoliation of bismuth sulphide show that exfoliation results in reduced sulphide stoichiometry and as such we apply the TFSI superacid treatment, previously successful on MoS2, to reduce sulphide vacancies and enhance the photoluminescence properties of exfoliated layers of Bi2S3.

You will work on so-called mechanical exfoliation by scotch-tape method in the chemistry lab, after which a chemical treatment is applied. After that, you will measure the optical properties of this material in our optics lab and analyse the data to learn about the fundamental photo-physical mechanism in this new class of materials.