Molybdenum Disulfide (MoS2) Crystals
MoS2 is a naturally-forming layered transition metal dichalcogenide that may be mined. It is a silvery-black crystal which looks and feels similar to crystals of graphite.
[Regular] One or two crystals | [Large] One crystal
[Regular] 0.7cm2 average area, or more | [Large] 2cm2 average area, or more
Each Mo(IV) center of MoS2 is occupying a trigonal prismatic coordination sphere, which is bound to six sulfide ligands. The sulfur center is connected to three Molybdenum centers, 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 that 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 that can glow or windows that 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 MoS2samples on your substrate, which can be viewed under a microscope.
In the above SEM images, you can see the layering of MoS2
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
1Adapted from the Wikimedia Commons file Molybdenite-3D-balls.png