Scale-up of Q-carbon and nanodiamonds by pulsed laser annealing

Q-carbon is a densely-packed metastable phase of carbon, which is harder than diamond. It is formed by nanosecond laser melting and ultrafast quenching of amorphous carbon films. The formation of Q-carbon is a strictly undercooling driven phenomenon and requires uniform sp(3)/sp(2) composition of as-deposited diamond-like carbon (DLC) films. This study illustrates the growth of wafer-scale DLC and its conversion into Q-carbon and diamond by nanosecond pulsed laser annealing (PLA). A two-dimensional transient heat conduction model was created to analyze the melt front and regrowth conditions of PLA processing, utilizing a temporal and spatial Gaussian heat source at a laser fluence of 800 mJ/cm(2). The transient temperature and melt-depth profiles obtained revealed successful melting of carbon with regrowth of Q-carbon phase. By optimizing laser plume energetics, uniformity in sp(3) content (similar to 40%) of DLC films was achieved, which led to the formation of Q-carbon over a large area. Here, the challenges associated with the scale-up of Q-carbon are discussed along with analysis of the interfacial bonding between the undercooled layers using atomic-force and electron microscopy techniques. The wafer scale-up of DLC films with controlled sp(3)/sp(2) content will be useful for making scalable Q-carbon based longer-lasting protective coatings and Q-carbon based electronic devices. These findings should help to further the development of Q-carbon and diamond-related materials technology for commercialization of high-performance systems.