Molybdenum Tungsten Diselenide (MoWSe2)

Our MoWSe2 alloys with the chemical formula MoxW(1-x)Se2 crystals perfectly crystallize in 2H phase and come at different alloy ratios x. Our crystals are grown using two different techniques through chemical vapor transport (CVT) or flux zone growth (see description of these two methods below) and their composition values were determined by XPS, SAED, and EDS measurements.. These crystals all possess extremely narrow PL bandwidths, display clean PL spectra, high carrier mobility, extremely clean and sharp XRD peaks, and negligible amount of defects (see published results as well as CVT vs. Flux based methods below ). These crystals come with guaranteed alloying and valleytronic response, sharp PL, and good electronic response. 

Important advantages of our crystals

1. Crystals come fully characterized using macro, micro, and nanoscale measurements (see below)

2. Thanks to our improved flux zone growth method, our crystals are homogeneously alloyed which means across the specimen you will only find one particular x composition.

3. No separation: Phase separation is commonly observed in 2D TMDCs alloys when cooling profiles are not controlled carefully. Our R&D team has worked over five (5) years to solely solve this problem. 

Properties of layered MoWSe2 alloys

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. 

http://meetings.aps.org/Meeting/MAR18/Session/K36.3

http://meetings.aps.org/Meeting/MAR17/Session/V1.14

Raman datasets collected from MoWSe2 alloys

Photoluminescence specturm collected from MoWSe2 alloys at 300K 

Publications from this product 

Summary: Publications from MIT, Berkeley, Stanford, Rice, and Harvard teams at top journals like Nature, Nature Communications, Nano Letters, and Advanced Materials

Control of Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers, Phys. Rev. Lett. 117, 187401 (2016)

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)

Y. Jin "A Van Der Waals Homojunction: Ideal p–n Diode Behavior in MoSe2" Advanced Materials 27, 5534–5540 (2015)

Tongay et. al. "Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons" Scientific Reports 3, Article number: 2657 (2013)

M. Yankowitz et. al. "Intrinsic Disorder in Graphene on Transition Metal Dichalcogenide Heterostructures" Nano Letters, 2015, 15 (3), pp 1925–1929

Tongay et.al. Thermally Driven Crossover from Indirect toward Direct Bandgap in 2D Semiconductors: MoSe2 versus MoS2; Nano Letters, 2012, 12 (11), pp 5576–5580

Manish Chhowalla, "Two-dimensional semiconductors for transistors" Nature Reviews Materials 1, Article number: 16052 (2016) doi:10.1038/natrevmats.2016.52

X Li et al. "Determining layer number of twodimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrates" Nanotechnology 27 (2016) 145704