Hafnium disulfide (HfS?) is an indirect gap layered semiconductor in the bulk and becomes direct gap semiconductor in monolayer form. They are designed and optimized in the last three years to achieve perfect industrial semiconductor grade materials with: 1) excellent stoichiometry, 2) large single domain size, 3) single phase materials without any mixed phases or amorphous content, 4) perfect layered crystal ideal for exfoliation purposes with impressive mosaic spread 0.08 degrees, 5) unmatched purity -semiconductor grade (5.5N), 99.9995%.

　　Typical characteristics of HfS2 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.