Controllable Synthesis Of Graphene

Graphene is one-atom-thick planar film of sp2-bonded carbon atoms densely arranged in a honeycomb crystal lattice. In 2004, Andre Geim and Kostya Novoselov first obtained graphene by micromechanical exfoliation of highly oriented pyrolytic graphite(HOPG), and in 2010 won the Nobel Prize in physics. The electron mobility of graphene has two orders of magnitude higher than that of silicon materials so that graphene is expected to replace silicon materials in semiconductor industry. It has attracted enormous scientific and technological interest due to the outstanding electrical, mechanical, and chemical properties as well as large potential in a multitude of applications. Graphene has the potential to be great useful in diverse technological application, In view of the different application field of graphene, controllable preparation of graphene challenges are put forward. At present, synthesis of graphene emerge in endlessly, but there are still many problems remain to be solved, so the optimization of preparation technology and the exploration of new method still has a huge space for development. However, it is quite challenging to obtain the graphene with large-scale, high-quality, free-transfer, easy to integration with semiconductor technology, well-controllable thickness and controllable doping. This paper around graphene growth has encountered problems, conducted a comprehensive research, mainly the following important research results:1. For the first time in the world, by ambient-pressure chemical vapor deposition(APCVD), large-scale and uniform depositon of high-quality graphene have been demonstrated directly on a germanium(Ge) substrate which is considered a promising channel material to replace conventional silicon in next-generation high-performance metal-oxide-semiconductor field-effect transistors(MOSFETs) due to its higher carrier mobility and process compatibility with Si-based microelectronics processes. Moreover, our technique bypass transfer step which may introduce defects, impurities, wrinkles, and cracks, thus potentially degrading the performance of graphene-based devices. Our technique is compatible with modern microelectronics technology thus allowing integration with high-volume production of complementary metal-oxide-semiconductors(CMOS).2. For the precise control of the thickness of graphene remains a major challenge, by taking advantage of the dual metal substrate of the Ni-coated Cu foils, the precise control of layer number of graphene by ion implantation has been demonstrated and the layer number of graphene strictly corresponds to the implantation fluence as expected. For instance, uniform monolayer graphene can be produced using a fluence of 4×1015 atoms/cm2, and a fluence of 8×1015 atoms/cm2 produces a bilayer graphene film. The formation mechanism is explored and confirmed by theoretical calculation. Superior to CVD method, our approach is less sensitive to the processing conditions, especially the thermal history, since the carbon content is solely determined by the implantation fluence. Given that the ion implantation is a mature technology in the current integrated circuit manufacturing, we believe that graphene synthesized by this strategy can expedite the industrial application of graphene.3. Because of its zero bandgap, graphene is highly limited in application as material of optical or electronic devices. Doping is considered as an efficient method to modulate the graphene bandgap, which breaks the symmetry structure of graphene with heteroatom to realize the modulation. Aims to overcome the difficulty of controllable graphene doping including doping type and content, we propose a method combined with implantation and CVD, by “heteroatom nucleation-promoting graphene regrowth” two-step dynamics way to fabricate doping-controllable lattice substitution graphene, study the mechanics of formation and evolution of heteroatom and graphene lattice, and research the relationship between structure and physical properties of doped graphene, to develop our research accordingly on some basic problem of doped grapheme, which will greatly improve the application of graphene in semiconductor device field.