List of publications out of this product listed below this page.
Our WSe2 crystals are treated as gold standards in 2D materials field. Our WSe2 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. Large single crystal defect free tungsten diselenide (WSe₂) crystals have been developed in our facilities. As they are single crystalline and industrial grade material, you do not need to worry about amorphous phase, defects, or contamination. The crystal size is large (~cm) and they are perfectly layered in the 001 direction (c-axis - see XRD pattern-) and thus it is very easy to exfoliate and yield monolayers with 1up to 100& yield rate. Single domain size is much larger than 100 microns which enables you to yield large monolayer areas.
The crystals were measured and confirmed by x-ray diffraction (XRD), x-ray photoelectron spectroscopy, Raman, photoluminescence, SIMS, and Auger electron spectroscopy techniques. In the monolayer form, our WSe₂ products show very strong PL at 1.67 eV and bilayers are also highly luminescent as shown in the PL spectrum images.
12 years of growth optimization: In these 12 years, we have perfected our WSe₂ 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.
See images for TEM, XRD, Raman, PL, optical, and SIM measurement results.
Partial List of Publications from This Product
Summary: Publications from MIT, Washington, MIT, Berkeley, Stanford, and Princeton teams at top journals like Nature Physics, Nature Nanotechnology, Nature Communications, Nano Letters, and Advanced Materials
Enabling valley selective exciton scattering in monolayer WSe2 through upconversion, Nature Communications, 8,14927 (2017)
Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers, Phys. Rev. Lett. 117, 187401 (2016)
Washington University - G. Aivazian et.al. "Magnetic control of valley pseudospin in monolayer WSe2" Nature Physics 11, 148–152 (2015)
Berkeley - M. Zhao et.al. "Large-scale chemical assembly of atomically thin transistors" Nature Nanotechnology 11, 954–959 (2016)
Tony Heinz – Stanford / Columbia University
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)
Andras Kis EPFL team "Valley Polarization by Spin Injection in a Light-Emitting van der Waals Heterojunction" Nano Letters 2016, 16, 5792−5797
Z. Li et. al. Layer Control of WSe2 via Selective Surface Layer Oxidation; ACS Nano, 2016, 10 (7), pp 6836–6842
Giant Enhancement of the Optical Second-Harmonic Emission of WSe2, Monolayers by Laser Excitation at Exciton Resonances; G. Wang, X. Marie, I. Gerber, T. Amand, D. Lagarde, L. Bouet, M. Vidal, A. Balocchi, and B. Urbaszek; Phys. Rev. Lett. 114, 097403 (2016)
M. Yankowitz et. al. "Intrinsic Disorder in Graphene on Transition Metal Dichalcogenide Heterostructures" Nano Letters, 2015, 15 (3), pp 1925–1929
Tongay et. al. "Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons" Scientific Reports 3, Article number: 2657 (2013)
T. Yan et. al. "Valley depolarization in monolayer WSe2" Scientific Reports 5, Article number: 15625 (2015)
G. Wang et.al. "Valley dynamics probed through charged and neutral exciton emission in monolayer WSe2" Phys. Rev. B 90, 075413 (2015)
X Li et al. "Determining layer number of twodimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrates" Nanotechnology 27 (2016) 145704
J. Wu- UC, Berkeley Anomalous Raman spectra and thickness-dependent electronic properties of WSe2 H. Sahin, S. Tongay, S. Horzum, W. Fan, J. Zhou, J. Li, J. Wu, and F. M. Peeters; Phys. Rev. B 87, 165409 (2013)
Duke University J. Huang et. al. "Probing the origin of excitonic states in monolayer WSe2" Scientific Reports 6, Article number: 22414 (2016)
Manish Chhowalla, "Two-dimensional semiconductors for transistors" Nature Reviews Materials 1, Article number: 16052 (2016) doi:10.1038/natrevmats.2016.52
G. Shepard et.al. "Nanobubble induced formation of quantum emitters in monolayer semiconductors" 2Dmaterials Accepted Manuscript