List of publications out of this product listed below this page
Our WS2 crystals are treated as gold standards in 2D materials field. Our WS2 crystals are notoriously known to possess extremely narrow PL bandwidths, display clean PL spectra, no bound exciton shoulders at low temperatures, high carrier mobility, and negligible amount of defects (see published results below).
[Starting 03/01/2017] To provide the highest quality crystals, 2Dsemiconductors Inc. will provide 2D TMDCs crystals grown by flux-based growth technique as a default. This method is well-known to produce materials with negligible amount of defects instead of chemical vapor transport (CVT) technique commonly used by other vendors in the field (http://meetings.aps.org/Meeting/MAR17/Session/V1.14). The CVT method is quick, easy, and high-yield growth technique, but relies on use of transporting agents such as TeCl4, Br2, I2, etc. which introduce a large amount of uncontrolled point defects in TMDCs crystals. These defects significantly impact electronic properties, device performance, valleytronic responses, and material properties. However, you may still request conventional CVT grown crystals by simply leaving a note in "comments box" during checkout.
Summary. Defect free tungsten disulfide (2H-WS₂) crystals have been developed in our facilities in the optical, electronic, and semiconducting grade %99.9995 certified purity. The crystal size is rather large (suffiicent for 1/2 - 1 year use) with large domain size and 0.1 degree mosaic spread (perfectly layered). and therefore they are ideal for exfoliating large size monolayers. Single domain size is much larger than 100 microns which enables you to yield large monolayer areas. Single crystal WS₂ are very easy to exfoliate and the monolayer yield is high (95% yield rate). The crystals were measured and confirmed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy, SIMS, Raman, photoluminescence, and Auger electron spectroscopy techniques. After exfoliation, single-layer WS₂ show strong PL at 2.05 eV.
12 years of growth optimization: In these 12 years, we have perfected our WS₂ growth to fit to your needs. We offer perfect stoichiometry, 100% H phase (no other hidden phases), no amorphous regions, superior domain sizes yielding large monolayers, strong light emission with established time-resolve photoluminescence and steady state light emission characteristics, and high electronic mobility. Our crystals have impressive semiconductor purity levels (99.9995 or higher) to bring you highest quality materials at large sizes.
* If you are looking for doped crystals, please refer to our 'doped 2D semiconductors' category from from the menu *
Partial List of Published Articles from This Product
Summary: Publications from MIT, Washington, MIT, Berkeley, Stanford, and Princeton teams at top journals like Nature Nanotechnology, Nano Letters, and Advanced Materials
T. Scrace et. al. "Magnetoluminescence and valley polarized state of a two-dimensional electron gas in WS2 monolayers" Nature Nanotechnology 10, 603–607 (2015) doi:10.1038/nnano.2015.78
J. He et. al. "Electron transfer and coupling in graphene–tungsten disulfide van der Waals heterostructures" Nature Communications 5, Article number: 5622 (2014)
Measurement of the optical dielectric function of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2, Yilei Li, Alexey Chernikov, Xian Zhang, Albert Rigosi, Heather M. Hill, Arend M. van der Zande, Daniel A. Chenet, En-Min Shih, James Hone, and Tony F. Heinz; Phys. Rev. B 90, 205422 (2014)
UT Austin - A. P. Nayak et. al. "Pressure-Modulated Conductivity, carrier Density, and Mobility of Multilayered Tungsten Disulfide" ACS Nano 10.1021/acsnano.5b03295
N. Peimyoo et. al. Nonblinking, Intense Two-Dimensional Light Emitter: Monolayer WS2 Triangles ACS Nano, 2013, 7 (12), pp 10985–10994
Manish Chhowalla, "Two-dimensional semiconductors for transistors" Nature Reviews Materials 1, Article number: 16052 (2016) doi:10.1038/natrevmats.2016.52
Tongay et. al. "Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons" Scientific Reports 3, Article number: 2657 (2013)
X Li et al. "Determining layer number of twodimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrates" Nanotechnology 27 (2016) 145704