石墨烯/铁电异质结构纵向器件性能研究

The extremely electrical properties, mechanical properties, optical properties,thermal properties make graphene a promising material in a wide range of applications.An obstacle to the use of graphene as an alternative to silicon electronics has been the absence of an energy gap between its conduction and valence bands, which makes it difficult to achieve low power dissipation in the OFF state.These low ratios are sufficient for individual analog electronics.The vertical graphene devices are made great attention due to large ON/OFF ratio. However, the effective regulation of the barrier height is relatively limited.In addition, the preparation vertical graphene device at this stage is hard for large-scale applications, and the device is also difficult to ensure reproducibility. In order to solve this question, we propose a new prepared method of vertical graphene/ferroelectric devices, with two directions of the ferroelectric polarization switching to modulate the ON/OFF ratio, and the development of new principles to achieve much larger ON/OFF ratio, while having the advantage of easy processing, large-scale potential application. In addition, We also proposes an effective graphene/ferroelectric devices simulation mechanism program. The simulation model of the vertical graphene/ferroelectric structure will provide direction for the prepared of the devices.

石墨烯由于其优异的电学性能、机械性能、光学性能、热学性能等成为当前的国际研究热点，然而由于完整的石墨烯没有带隙，在模拟电路上不饱和，因而其开关比很低，极大地限制了它在数据逻辑电路的应用。石墨烯纵向结构由于其具有较大的开关比 ，而受到广大研究人员的极大关注。然而，该势垒的有效高度调控也比较有限。另外，石墨烯纵向器件的制备在目前阶段还难以用于大规模应用，同时器件的重复性难以保证。为此，本项目提出一种石墨烯/铁电纵向的制备方案，用铁电的两个极化方向来二次调控开关比ON/OFF，发展了新的原理来实现石墨烯纵向器件更大开关比的调控，同时其具有易于加工的优点，有大规模应用的潜力。另外，本项目还提出一套有效的石墨烯/铁电纵向器件机理模拟程序。对石墨烯/铁电结构纵向结构中隧穿输运进行有效的模拟仿真，为器件的制备提供方向性。

石墨烯等二维材料具有优异的电、光、热等性能。此类材料的纵向结构相较于其平面结构往往会表现出更加独特的性质。本项目在生长出石墨烯的基础上，采用倒置工艺，将生长石墨烯与CMOS工艺集成，制备了埋栅石墨烯场效应晶体管。基于此晶体管，国际上率先制备出了石墨烯双平衡混频器电路及四节分布式放大器电路。同时，项目还采用化学气相淀积的方法，第一次制备出了大面积、均匀、垂直的二硫化钼，并对其特性进行了表征。基于此，进而制备了石墨烯/二硫化钼纵向异质结构，以期解决石墨烯禁带宽度为零造成的晶体管开关比低的问题。. 采用倒置工艺将石墨烯与CMOS工艺集成，解决了石墨烯工艺与CMOS工艺不兼容的问题。项目所制备的埋栅石墨烯场效应晶体管结构，获得了最高36.5 GHz的震荡频率，此外，具有不同栅长的器件均获得与fT接近的fmax，500nm栅长石墨烯晶体管的截止频率fT达到了17GHz。该结果发表在了Scientific Reports, 6, 35717, (2016)上。基于此晶体管，我们制备了石墨烯双平衡混频器电路及四节分布式放大器电路。其中，四管双平衡混频器的线性度高至21 dBm，该指标处于国际领先水平。该结果发表在了Nano letters, 15, 6677 (2015)。所制备垂直硫化钼的开启电场2.46V/μm，场发射电流达到了10μm/cm2。电场增强因子高达6240。所制备硫化钼在析氢反应中的交换电流密度达到了22.3μA/cm，比块状硫化钼高出了约70倍。该结果发表在了Scientific Reports, 6, 21171, (2016)上。该篇文章两年内受到多次引用，根据Web of Science的检索结果，为“热点论文”。