SPI Supplies^® Brand Moly Disulfide (MoS₂)

High quality sheaf like and cleavable single crystals!

CAS #: 1317-33-5
MoS₂
RTECS No.: QA4697000
Specific Gravity: 4.8

SPI Molybdenum Disulfide, Single Crystals

Consider the latest addition to the SPI family of substrate products for AFM, STM, and even thin film coatings research. These newly added crystals compliment the other substrate materials useful for SPM studies and already offered by SPI Supplies: SPI Supplies^® Brand fine mica and SPI Supplies Brand of HOPG (Highly Ordered Pyrolytic Graphite).

Who would want to use MoS₂?
A growing number of users of STM and AFM are finding this to be the substrate of choice for looking at organic molecules, which bind nicely to MoS₂. We are talking about binding properties that are far greater than for either mica or HOPG.

A few words about MoS₂ generally:
This is a 100% "natural" material, it is taken out of the ground and in most instances, it is ground up into a fine powder to be used for its well documented lubrication properties. It is much more of a challenge to find MoS₂ in sufficiently large crystal form that it can be used as a substrate material.

MoS₂ exhibits a lamellar or layer-like structure, with inter-lamellar bonding between two adjacent layers of sulfur atoms. Van der Waals forces between the layers is quite weak, meaning that the layers are easily pulled apart, just as is the case for mica. This is also the enabling feature that makes possible the property of "micaceous cleavage".

The thermal stability of MoS₂ in non-oxidizing environments is approximately of the order of 1100° C, but in air, oxidation starts to become appreciable at roughly 350 - 400°C. The normal air oxidation product is MoO₃.

Where does MoS₂ come from?
The two main deposits in the world are in Australia and Canada (Otter Lake, Ontario), the latter the source of the SPI material. The SPI MoS₂ is collected by a professional geologist with strong academic ties and with a particular background in this mineral. Each single crystal that is sold by SPI Supplies has been individual inspected and graded and only those passing the test of optical clarity and dimensions as well as aesthetic appearance are selected and packaged into the unique SPI Supplies membrane boxes.

What are the physical characteristics?
The SPI MoS₂ "cleaves" in a way that is quite analogous to the cleaving of either "fine mica" or HOPG. Hence for the researcher, it is fairly easy to obtain a freshly cleaved surface for critical samples and research. SPI Supplies furnishes extensive additional characterization of the MoS₂ offered for these applications. MoS₂ is generally described as being insoluble in water but it is soluble in hot water, aqua regia, HNO₃. It is insoluble in dilute acids and concentrated H₂SO₄.

What do the cleavings look like?
Actually, they are obtained very much like the way one would obtain cleavings from HOPG: With a piece of 3M^® Brand "Magic" adhesive tape just press firmly onto the MoS₂ the tape, and then with one smooth and continuous "pull", lift off the "cleaving" or "cleaved layer."

The photo demonstration is actually a worst case example, and represents what one would obtain from their first cleaving of the originally rough surface. Further cleavings will result in a somewhat larger cleaved surface area.

Just what kind of phenomenon is this?
Well, in some respects it is very analogous to the cleavage of mica and in other respects, it is more like the cleaving of HOPG. It is analogous to the cleaving of mica in the sense that there is nice "basal plane cleavage". However, the regularity and size of the MoS₂ crystals is much less than typically even for a low grade mica so the user should not have unrealistic expectations in this respect. It is analogous to HOPG in the way the freshly cleaved surface is made, namely with the use of a tape stripping procedure.

What kind of characterization work has been done on the SPI MoS₂?
Being a natural product, and also, given the well known way properties and characteristics can vary from point to point, we can only report the results of analyses done on what would appear to be similar samples, but not necessary the exact pieces available for purchase.

By EDS, the only peaks seen are from the Mo_L and S_{K_α} We have done this kind of analysis on some number of these "pieces" or "sheafs" but we can not guarantee that the specific piece(s) a customer would be receiving would have that same composition. Based on our data so far, we have confidence that the purity is better than 99+%.

And because of the natural origins of the SPI MoS₂, no two pieces are going to be exactly the same size. Hence we offer the material in pieces that are "large", "medium" and "small" with minimum size specifications on each.

Each piece of the SPI molybdenum disulfide is packed in its own " membrane box" for long term storage and safekeeping. Note that the dimensions given below are minimum dimensions and in general, the crystal you receive will be larger than the minimum stated dimensions.

SPI Supplies^® Brand Moly Disulfide (MoS₂)

Minimum size	SPI #	Each	10+, Each	In Stock
Large (20x10 mm)	429ML-AB	$ 219.59	$ 197.63	Yes
Medium (15x9 mm)	429MM-AB	153.71	138.34	Yes
Small (8 x 8 mm)	429MS-AB	87.85	79.07	Yes

Storage conditions: Room temperature
Non-hazardous from stand point of shipping

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SPI Supplies® Brand Moly Disulfide (MoS2)

SPI Molybdenum Disulfide, Single Crystals

SPI Supplies^® Brand Moly Disulfide (MoS₂)