p-type WSe2 Crystal

WSe2 is a semiconductor with an indirect band gap of 1.25 eV in the bulk and 1.62 eV direct optical band gap semiconductor in the monolayer form. Its electronic (single particle) band gap is located at ~2.0 eV with an excitonic binding energy of 0.4 eV. WSe2 layers are stacked together via van der Waals (vdW) interactions which enables them to be exfoliated down to monolayers. p-type WSe2 crystals contain Nb doping (~1E16cm-3 to 1E17 cm-3) to sustain p-type behavior, and are treated as gold standards in 2D materials field. WSe2 crystals from 2Dsemiconductors are known for its superior valleytronic performance, perfect crystallization, defect free structure, extremely narrow PL bandwidths, clean PL spectra (free of bound exciton shoulders), and high carrier mobility. Our WSe2 crystals are grown either flux zone or chemical vapor transport techniques. If your application is solely focusing on optics, photonics, and quantum optics, we strongly recommend flux zone grown WSe2 crystals owing to their perfect crystallinity and extremely low defects concentrations. Thousands of scientific articles have cited us and used these crystals for scientific accuracy and clean signals. 

Typical characteristics of WSe2 crystals from 2Dsemiconductors

Growth method matters> Flux zone or CVT growth method? Contamination of halides and point defects in layered crystals are well known cause for their reduced electronic mobility, reduced anisotropic response, poor e-h recombination, low-PL emission, and lower optical absorption. Flux zone technique is a halide free technique used for synthesizing truly semiconductor grade vdW crystals. This method distinguishes itself from chemical vapor transport (CVT) technique in the following regard: CVT is a quick (~2 weeks) growth method but exhibits poor crystalline quality and the defect concentration reaches to 1E11 to 1E12 cm-2 range. In contrast, flux method takes long (~3 months) growth time, but ensures slow crystallization for perfect atomic structuring, and impurity free crystal growth with defect concentration as low as 1E9 - 1E10 cm-2. During check out just state which type of growth process is preferred. Unless otherwise stated, 2Dsemiconductors ships Flux zone crystals as a default choice.  

XRD data collected from WSe2 crystals

Raman spectrum collected from WSe2 monolayers

Photoluminecence spectrum collected from monolayer WSe2 exfoliated from WSe2 crystals

SIMS purity datasets collected from WSe2 crystals

 HRTEM images collected from WSe2 crystals

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 volume 8, Article number: 14927 (2017), doi:10.1038/ncomms14927

Enabling valley selective exciton scattering in monolayer WSe2 through upconversion, Nature Communications, 8,14927 (2017) 
doi:10.1038/ncomms14927

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