Synthesis and Transfer of Single-Layer Transition Metal Disulfides on Diverse Surfaces Yi-Hsien Lee, †,‡ Lili Yu, † Han Wang, † Wenjing Fang, † Xi Ling, †,∥ Yumeng Shi, † Cheng-Te Lin, ‡ Jing-Kai Huang, ‡ Mu-Tung Chang, § Chia-Seng Chang, § Mildred Dresselhaus, †,∥ Tomas Palacios, † Lain-Jong Li,* ,‡ and Jing Kong* ,† † Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge Massachusetts 02139, United States ‡ Institute of Atomic and Molecular Sciences, Academia Sinica, No. 1, Roosevelt Rd., Sec. 4, Taipei, 10617, Taiwan § Institute of Physics, Academia Sinica, 128 Sec. 2, Academia Rd., Nankang, Taipei 11529, Taiwan ∥ Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States * S Supporting Information ABSTRACT: Recently, monolayers of layered transition metal dichalcoge- nides (LTMD), such as MX 2 (M = Mo, W and X = S, Se), have been reported to exhibit significant spin-valley coupling and optoelectronic performances because of the unique structural symmetry and band structures. Monolayers in this class of materials offered a burgeoning field in fundamental physics, energy harvesting, electronics, and optoelectronics. However, most studies to date are hindered by great challenges on the synthesis and transfer of high-quality LTMD monolayers. Hence, a feasible synthetic process to overcome the challenges is essential. Here, we demonstrate the growth of high-quality MS 2 (M = Mo, W) monolayers using ambient-pressure chemical vapor deposition (APCVD) with the seeding of perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS). The growth of a MS 2 monolayer is achieved on various surfaces with a significant flexibility to surface corrugation. Electronic transport and optical performances of the as-grown MS 2 monolayers are comparable to those of exfoliated MS 2 monolayers. We also demonstrate a robust technique in transferring the MS 2 monolayer samples to diverse surfaces, which may stimulate the progress on the class of materials and open a new route toward the synthesis of various novel hybrid structures with LTMD monolayer and functional materials. KEYWORDS: Metal dichalcogenides, 2D materials, monolayer, transfer L ayered transition metal dichalcogenides (LTMD), includ- ing MX 2 (M = Mo, W; X = S, Se), have attracted extensive research efforts in the fields of nanotribology, catalysis, energy harvesting, and optoelectronics. 1−11 Monolayers of two-dimen- sional crystals, such as graphene, have been highlighted regarding both scientific and industrial aspects due to novel physical phenomenon inherited from the reduced dimension- ality. 12 Similarly, the broken inversion symmetry and the indirect-to-direct bandgap transition of LTMD are observed when the dimension is reduced from multilayers to a monolayer. 13−15 The LTMD monolayers, being considered as the thinnest semiconductor, exhibit great potential for advanced short-channel devices. 11 The transistor fabricated with an exfoliated MoS 2 monolayer displays a high on−off current ratio and good electrical performance, which are both necessary for electronic circuit requiring low stand-by power. 10 Recent theoretical predictions suggest that the dissociation of H 2 O could be realized at defects of single layer MoS 2 , which is critical for developing clean and sustainable energy from hydrogen. 16 Moreover, monolayer MoS 2 and WS 2 have been considered as an ideal material for exploring valleytronics and valley-based optoelectronic applications. 17−20 The broken inversion symmetry of the monolayer and the strong spin− orbit coupling lead to a fascinating interplay between spin and valley physics, enable simultaneous control over the spin and valley degrees of freedom, and create an avenue toward the integration of spintronics and valleytronics applications. Considerable efforts have been devoted to synthesize an MoS 2 monolayer, including various kinds of exfolia- tions, 10,14,15,22,23 physical vapor deposition, 8,24 and chemical vapor deposition (CVD) approaches. 25−27 Recently, a CVD- MoS 2 monolayer was presented with sulfurization of the thin Mo layer 26 and the layer growth induced using fragments of reduced graphene oxide as seeds. 25 However, the as-grown layers display obvious thickness variations, and their optoelec- Received: February 22, 2013 Published: March 18, 2013 Letter pubs.acs.org/NanoLett © 2013 American Chemical Society 1852 dx.doi.org/10.1021/nl400687n | Nano Lett. 2013, 13, 1852−1857