Nanoscale PAPER Cite this: Nanoscale, 2014, 6, 12792 Received 25th July 2014, Accepted 2nd September 2014 DOI: 10.1039/c4nr04228j www.rsc.org/nanoscale Scalable high-mobility MoS 2 thin films fabricated by an atmospheric pressure chemical vapor deposition process at ambient temperature Chung-Che Huang,* a Feras Al-Saab, a Yudong Wang, b Jun-Yu Ou, a John C. Walker, c Shuncai Wang, c Behrad Gholipour, a Robert E. Simpson d and Daniel W. Hewak a Nano-scale MoS 2 thin films are successfully deposited on a variety of substrates by atmospheric pressure chemical vapor deposition (APCVD) at ambient temperature, followed by a two-step annealing process. These annealed MoS 2 thin films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS-NIR spectrometry, photoluminescence (PL) and Hall Effect measurement. Key optical and electronic properties of APCVD grown MoS 2 thin films are determined. This APCVD process is scalable and can be easily incorporated with conventional lithography as the deposition is taking place at room temperature. We also find that the substrate material plays a significant role in the crystalline struc- ture formation during the annealing process and single crystalline MoS 2 thin films can be achieved by using both c-plane ZnO and c-plane sapphire substrates. These APCVD grown nano-scale MoS 2 thin films show great promise for nanoelectronic and optoelectronic applications. Introduction The unprecedented electronic properties offered by graphene, a monolayer of graphite arranged in a honeycomb lattice, are attracting increasing interest for new applications in nano- scale electronics. However, the zero bandgap of graphene has restricted its use in some optoelectronic applications. 1,2 Recently, transition metal dichalcogenides (TMDCs), two- dimensional layered materials, such as MoS 2 , MoSe 2 , WS 2 and WSe 2 have become a noteworthy complimentary material to graphene sharing many of its properties. 3 They offer properties that are unattainable in graphene, in particular providing a tuneable bandgap transition from indirect to direct within the single layer. This property has led to the demonstration of TMDCs in applications such as transistors, photodetectors, electroluminescent, and biosensing devices. 1–7 With advances in nano-scale materials characterization and device fabrica- tion, there are a host of new opportunities to design nanoelec- tronic and optoelectronic devices based on these two- dimensional TMDCs thin films. This is especially true for MoS 2 , which has a strain tunable band across the solar spectrum. 8 Existing preparation methodologies for MoS 2 thin films include exfoliation by micromechanical methods or in solu- tion, 2,4,9,10 physical vapor deposition, 11 hydrothermal syn- thesis, 12 electrochemical synthesis, 13 sulfurization of molybdenum oxides, 14 thermolysis of the precursor containing Mo and S atoms, 15 and chemical vapor deposition. 16,17 In a very recent report 17 by Y. Yu et al., a self-limiting chemical vapor deposition method was used to fabricate MoS 2 films ranging from a monolayer to several layers of MoS 2 . The films were, however, polycrystalline and the carrier mobility was rela- tively low, in the range 0.003 to 0.03 cm 2 V -1 s -1 . In addition, the color of the fabricated monolayer or bilayer MoS 2 thin films on sapphire substrates 17 was much darker than expected. The majority of MoS 2 films fabricated by the aforemen- tioned techniques are in the form of flakes, typically only a few hundred square microns in area. The current challenge in the fabrication of MoS 2 thin films is to form an industrially scal- able and controllable deposition methodology. 1,18 CVD tech- nology has the advantage of offering conformal, scalable, and controllable thin film growth on a variety of different sub- strates. APCVD has been used to fabricate MoS 2 and WS 2 nano- materials at the temperatures between 200 °C to 900 °C. 19 a Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK. E-mail: cch@orc.soton.ac.uk b Nano Group, Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ, UK c nCATS, Engineering and the Environment, University of Southampton, Southampton, SO17 1BJ, UK d Engineering Product Development, Singapore University of Technology and Design, 20 Dover Drive, Singapore 138682 12792 | Nanoscale, 2014, 6, 12792–12797 This journal is © The Royal Society of Chemistry 2014 Published on 04 September 2014. Downloaded by University of Southampton on 31/01/2017 09:17:08. View Article Online View Journal | View Issue