Abstract
Two-dimensional(2D) materials have attracted a great attention due to their high performancefor several applications. Graphene with ultra high mobility, excellent conductivity and strength at few atomic layers, made it the first and the most well-known 2D material. Further development in other layered materials also reported interesting results upon electron confinement in 2D materials while the thickness is approaching to single atomic layer. In particular, transition metal dichalcogenides (TMDs) based on Mo and W as transition metal, displaya transition to direct-gap for potential applications in optoelectronicsand energy harvesting. Despite that Chemical Vapor Deposition (CVD) is the most common way to synthesize 2D materials, several obstacles should beovercome. The high temperature and the required transfer process are the major issues to be addressed. The high temperature induces damage and limit the number of possible substrates used for the operation and the transfer process creates wrinkles and marks in the transferred film. Novel methods to grow and pattern graphene and TMDs with atomic thickness are an important step to pursue. In this study the use of laser was explored as a novel method for the synthesis of graphene and MS2 (M=W, Mo) with atomic thickness. In the first part, a layer structure to directly synthesize few layer graphene on insulating substrates by laser irradiation, inducing local heating, is suggested.Tuning the metal layer thickness and laser power at different scanning rates, the number of graphene layers can be tuned. In order to overcome the limitation the resolution of the laser beam, submicrometer resolution of graphene can be achieved by patterning the intermediate metal layer usingstandard lithography methods. Furthermore, hole and electronmobilities of 500 and 950 cm2 V −1 s −1were measured. Laser annealing provides a one step process to directly grow graphene on insulators without required transfer. In the second part, two kinds of TMDs-WS2 and MoS2 were synthesized successfully underneath an oxide layer, acting as a protective layer. Raman, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were applied to validate the presence and the numbers of layers. In addition, the simple structure of photo-sensing devices made of the WS2 denotes potential for mass-production. Additionally, this approach may apply to other kinds of TMDs materials by choosing the corresponding precursors.