Growth parameter enhancement for MoS₂ thin films synthesized by pulsed laser deposition

Abstract

Two‐dimensional materials such as graphene and MoS2 have been the main focus of intense research efforts over the past few years. The most common method of exfoliating these materials, although efficient for lab‐scale experiments, is not acceptable for large area and practical applications. Here, we report the deposition of MoS2 layered films on amorphous (SiO2) and crystalline substrates (sapphire) using a pulsed laser deposition (PLD) method. Increased substrate temperature (∼700 °C) and laser energy density (>530 mJ /cm2) promotes crystalline MoS2 films < 20 nm, as demonstrated by fast Fourier transform (FFT) and transmission electron microscopy (TEM). The method reported here opens the possibility for large area layered MoS2 films by using a laser ablation processes. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Large-Area Pulsed Laser Deposited Molybdenum Diselenide Heterojunction Photodiodes

“…However, the MoSe 2 film has many particles, as seen in the optical images in Figure S1a–c. A study by Serna et al shows that changing the target rotation speed during the pulsed laser deposition can reduce the density of particles on the film surface . To reduce the number of particles, a study reducing the target rotation speed from 5 rpm to 3.33 rpm as well as 1.67 rpm was carried out and is shown in Figures S2a and S1d–f, respectively.…”

“…Pulsed laser deposition (PLD), a physical vapor deposition (PVD) technique, is an alternate method that is gaining more interest in recent years . Tuning PLD parameters such as substrate temperature, laser energy density, chamber pressure, gas environment, and target rotation speed can result in high-quality 2D TMDs. , PLD is a fast deposition process in which a high-power laser is used to ablate the desired target and deposit the material on a selected substrate while maintaining the same stoichiometry from target to substrate under optical deposition parameters due to absorption of the laser on a localized area of the target. This ablation results in a plasma directed at the target surface where the material deposits .…”

Large area few-layer TMD film growths and their applications

“…It operates on the principle of using a laser to ablate particles from a bulk sample of the desired material, the particles then condense on a substrate under high vacuum (~10 −6 Torr) to form thin films [48] (figure 3). While CVD growths require reaction temperatures around 800 • C-1000 • C, PLD growths can comfortably occur around 500 • C [3,7,49]. In addition, the laser will precisely ablate a certain amount of material, and so can be 'pulsed' to achieve fine control on the final layer count of the product.…”

“…Growths occurred at 700 • C, with a monolayer being synthesized in a relatively quick 5 min [50]. Serna et al [49] explored the effect of growth temperature, attempting temperatures from 700 • C down to 300 • C. They observed that the stoichiometric ratio of Mo to S suffered at lower temperatures, with S atoms lacking [49]. They hypothesized that the reaction kinetics at lower temperatures favored S being ablated from the sapphire growth substrate [49].…”

“…Serna et al [49] explored the effect of growth temperature, attempting temperatures from 700 • C down to 300 • C. They observed that the stoichiometric ratio of Mo to S suffered at lower temperatures, with S atoms lacking [49]. They hypothesized that the reaction kinetics at lower temperatures favored S being ablated from the sapphire growth substrate [49]. Even so, large area films formed at temperatures far too low for CVD reactions, hinting that further optimization may make such efficient growths possible.…”