Large area growth of layered WSe₂ films

Growth of smooth and continuous films of WSe₂ has been demonstrated by employing atomic layer deposition (ALD) on 5 cm × 5 cm substrates. The substrates consisted of silicon wafers with a layer of SiO₂. The ALD precursors were WCl₅ and H₂Se. The film properties characterized using Raman spectroscopy and x-ray photoelectron spectroscopy are comparable to those reported for WSe₂ films produced by chemical vapor deposition and exfoliation. Carrier mobilities were determined with back-gated transistors. With Pd contacts, median electron and hole mobilities of 531 cm² V⁻¹ s⁻¹ and 354 cm² V⁻¹ s⁻¹, respectively, were measured. (paper)