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Molybdenum Disulfide (MoS₂) Crystals

MoS₂ is a naturally-forming layered transition metal dichalcogenide which may be mined. It is a silvery-black crystal which looks and feels similar to crystals of graphite.

Properties:

• Single crystal
• 2cm² average area, or more
• purity: >99%

Each Mo(IV) center of MoS₂ is occupying a trigonal prismatic coordination sphere, which is bound to six sulfide ligands. The sulfur centre is connected to three Molybdenum centres, which are pyramidal. The trigonal prisms are layered, sandwiching molybdenum atoms between layers of sulfur atoms.

Depiction of MoS₂ Crystal Structure¹

MoS₂ has a number of unique properties which allow it potential applications in transistors, flexible displays, and optics. For one, it possesses a direct bandgap, which is necessary for most transistor applications. It also has unique optical properties, namely having a high level of photoluminescence; this property gives it potential applications in making walls which can glow or windows which display images. It being an ultra-thin, transparent, flexible conductor makes it a likely material-of-choice for transparent, flexible displays.

MoS₂ may be mechanically exfoliated using scotch tape to create 2D MoS₂ samples, similarly to graphene. To do this, use a piece of scotch tape, and press a thin piece of MoS2 to it. Then, take the other end of the tape and stick it together with the tape with MoS2 on it. Do that several more times, eventually sticking the tape to a clean substrate (such as a Si/SiO2 wafer) and peel it back. You will then have multi and monolayer MoS2 samples on your substrate, which can be viewed under a microscope.

In the above SEM images, you can see the layering of MoS₂

Academic reference:

Single-Layer MoS2 Transistors, Radisavljevic et al., Nature Nanotechnology, 2011, 6 (March). pp 447-500

Stretching and Breaking of Ultrathin MoS2, Bertolazzi et al., ACS Nano, 2011 (12), 5. 9703-9709