In situ imaging and control of layer-by-layer femtosecond laser thinning of graphene Available to Purchase

Although existing methods (chemical vapor deposition, mechanical exfoliation, etc.) are available to produce graphene, the lack of thickness control limits further graphene applications. Laser-thinning is a new technique for modifying graphene and other related two-dimensional (2D) layered nanomaterials. In this study, we demonstrate an approach to precise thinning of graphene films to a specific thickness using a femtosecond (fs) laser raster scanning. By controlling laser fluence and scanning duration, graphene thinning with an atomic layer precision, namely layer-by-layer graphene removal, has been realized. Graphene with smooth surface and controlled thickness is produced. An fs-laser-based four-wave mixing (FWM) system is developed that is capable of distinguishing graphene of different thicknesses and counting the number of layers using the linear relationship between the FWM signal intensity and the graphene thickness, which is more accurate and much faster than Raman microscopy. Furthermore, FWM imaging has been successfully applied to achieve in situ, real-time monitoring of the fs laser graphene thinning process based on the large optical nonlinearity of graphene. This method can not only realize large-scale thinning of various 2D nanomaterials with atomic layer precision, but also provide in situ, rapid imaging capability of 2D nanomaterials for accurate assessment of the number of layers.