聚合物辅助沉积高浓度原位掺杂石墨烯薄膜的研究

Graphene is expected as candidate for silicon in the next generation transistors, and open up a band gap for graphene is the key to achieve that. Previous works proved doping with B/N heteroatoms is capable to open up the band gap of graphene, but higher doping concentration is needed for opening it enough for transistor applications (>0.4 ev). As the structure of graphene is ultra-stable and the energy barrier for B/N heteroatoms entering graphene lattice is high, the fabrication of heave in-situ doped graphene through current approaches is still a challenge. In this proposal, a polymer assisted homogeneous solution method is applied to tune the deposition of doping graphene from molecular level. Chemical active small molecules such as glucose and urea are applied as precursors, and heave doping could be realized base on that the precursors tend to bond with each other and forming stable C-N bonds and B-C bonds through pre-treatment. Most importantly, a kind of water solvable polymer is applied to assist the film coating and growth process, which help to yield high crystalline graphene thin film. Based on an early stage of feasibility study, the polymer assisted deposition method is of great potential to generate heave doping and fine crystalline graphene. And the accomplishment of this proposal will greatly advance the study about graphene electric transport properties band gap tuning.

为了实现石墨烯代替硅应用于新一代超微晶体管，打开石墨烯的能隙是关键。前人的工作证明硼/氮等异质原子掺杂在打开石墨烯能隙方面是有效的，然而为了能够打开一个足够应用于晶体管的能隙（大于0.4 ev），掺杂浓度还需要进一步提高。由于石墨烯的结构非常稳定，硼/氮原子进入石墨烯晶格的能垒较高，现有的实验手段在制备高浓度原位掺杂石墨烯方面依然有困难。我们将发展聚合物辅助均相溶液体系，从分子层面上调控掺杂石墨烯薄膜的生长。该方法选择活性位点多、易反应成键的葡萄糖、尿素等水溶性小分子为前驱体，通过预处理使它们先形成稳定的C-B、C-N键，为实现高浓度原位掺杂提供了基础；另一方面，应用聚合物辅助法控制前躯体分子在催化金属基底上的成膜和生长，为制备高质量石墨烯薄膜提供保障。该方法在制备高质量、高浓度原位掺杂石墨烯方面非常有发展潜力，其成功应用能够为进一步研究石墨烯能隙和电输运性能的调控提供强有力的实验支持。

利用聚合物辅助沉积法，我们实现了本征石墨烯薄膜以及B/N共掺杂石墨烯的制备，通过调节B/N元素的掺杂比例，石墨烯薄膜的光学带隙由0 ev增加到1.64 ev，且其载流子由N型转变为P型，充分证明了聚合物辅助沉积法制备B/N共掺杂石墨烯薄膜并调控其性能的可行性。其次制备了一种结构、性能都介于玻璃碳与石墨烯之间的薄膜——玻璃化石墨烯薄膜，不仅表面非常平整（粗糙度<1 nm），连续、均匀、致密，且具有接近石墨烯薄膜的光学与电学性能，具有优异的机械稳定性、化学稳定性与热稳定性。然后我们利用激光辅助打印，实现了玻璃化石墨烯薄膜的打印。通过将打印的玻璃化石墨烯转移到柔性基底上，研究了玻璃化石墨烯图案的柔韧性与可靠性。利用红外激光直写辅助，实现了石墨烯图案的打印，并将打印的石墨烯图案转移到柔性基底上、对其可拉伸、可弯折的性能进行了研究。此外，利用红外激光裁剪的方法制备石墨烯微结构，进一步提高了石墨烯薄膜在应用于透明导电电极方面的品质因子。