化学气相沉积生长厘米级高迁移率石墨烯单晶的研究

Graphene, a new material with great application potential, has stimulated intense research interest owing to its unique physical and chemical properties. Fabrication techniques for wafer scale graphene are already available. However, the quality of graphene in wafer scale differs from that of normal silicon as the fabrication of high quality and large size graphene single crystal preparation is s still a great challenge. In this study, we demonstrated a simple but efficient strategy to synthesize centimeter-sized graphene single crystal grains by regulating the supply of reactants in chemical vapor deposition process. The gradual increase in the temperature of carbon source and the flow rate of hydrogen were adapted to control the nucleation density andt drive the continuous growth of graphene grains. Meanwhile, the first principle calculations and chemical vapor reaction kinetics were introduced to set up the ?uid dynamics mechanism to explain the single crystal graphene growth process. The graphene-based back-gate ?eld-effect transistors (FETs) were fabricated on 300 nm SiO2/Si substrates to investigate the electronic properties of hexagonal millimeter-sized graphene domains. The considerable research on graphene has motivated the scalable production of high-quality graphene and graphene devices.

石墨烯作为具有巨大应用潜力的新型材料，是当前物理、化学和材料等研究和应用领域的热点课题。然而相比于成熟的晶圆级单晶硅的制备工艺，目前高质量和大尺寸石墨烯单晶的制备尚无法实现。本项目提出采用聚苯乙烯作为固态碳源，采用化学气相沉积的方法在金属基底上培育出厘米级高迁移率石墨烯六角单晶畴。通过控制不同生长阶段的反应基元的浓度和平均自由程，以及多步生长方式达到控制石墨烯单晶形核密度的控制和晶畴持续快速生长的目的。同时结合第一性原理计算和化学气相反应动力学理论建立石墨烯单晶畴培育过程中的动力学模型，并探讨影响大尺寸石墨烯单晶畴生长的微观机理。在实现厘米级石墨烯单晶制备和催化生长机制的系统化分析的基础上开展石墨烯电学输运特性及场效应的研究。这项研究为性能优良且成本低廉的新一代碳基微纳电子器件的研制与开发提供了关键技术和实验基础。

单晶硅是微电子技术发展的基石，而单晶石墨烯则是其在电子学领域规模化应用的前提。铜表面催化生长无法实现单核控制，因而制备的薄膜一般为多晶，且生长速度随着时间的推移逐渐变慢。此前铜衬底上制备的最大石墨烯单晶尺寸约为一厘米，且需要较长的生长时间。本研究通过向具有一定溶碳能力的Cu85Ni15合金局域提供碳源，产生局部碳浓度过饱和，成功解决了石墨烯单个核心控制形核这一技术难题。通过同位素技术发现了Ni-Cu合金表面石墨烯等温析出的新机制。经过2.5小时生长成功制备得到1.5英寸的石墨烯单晶，生长速度和单晶大小都创造了世界纪录。通过单核控制制备晶圆级石墨烯单晶可以视为是三维硅单晶技术在二维材料中的再现，也为其他二维材料的晶圆级单晶生长提供了借鉴。该研究成果对于推动石墨烯在微电子领域的大规模应用奠定了基础。