The Growth of Graphene on Nickel Silicide Substrates

Graphene is a two-dimensional crystal of carbon atoms packed in a honeycomb structure with the sp2 bonding, and it has been in the focus of intensive researches due to its unique physical properties. For almost ten years, the synthesis of large-area high-quality graphene has been an important issue, but there still remain some problems in the most routinely used chemical vapor deposition (CVD) process. First of all, the high growth temperature in the CVD method is unfavorable for integrating it with the current Si-based semiconductor technology. Secondly, even graphene can be grown on other metal substrates, the application of graphene still requires complicated transfer procedures, in which graphene is easily damaged and degraded. In this research, we propose to use various nickel silicide thin films on Si (111) wafer as the growth substrate, such as Ni2Si, NiSi and NiSi2. Since nickel silicides have been used as metal contacts in very-large-scale integration (VLSI) technology for more than 30 years, there is a great opportunity to integrate graphene into the technology. In this study, graphene growth is conducted in an ultra-high vacuum CVD (UHVCVD) system. The catalytic abilities of the three silicides are compared in two different growth methods, including the CVD and solid-phase precipitation method. We find that Ni2Si has the best catalytic ability. We also find that coronene with a polycyclic structure can further enhance the formation of C-C sp2 and sp3 bonding for the growth of carbon materials. In this work, we use transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to study the surface morphology and crystal quality of the nickel silicide substrates. We also use Raman spectroscopy to evaluate the quality of graphene.