基于二维材料量子电容器的电致可调谐振电路

Quantum capacitance describes the self-charge/discharge effects of materials when electrons are filling the Fermi level driven by an electric potential. Distinguished from the concept of traditional capacitance, the quantum capacitance is restricted by quantum phenomena, such as the Pauli exclusion principles. The discovery of two-dimensional (2D) materials have made 2D material an excellent platform for investigating quantum capacitance, due to the atomically thin thickness and ultra-low density of states. The quantum capacitance measurement has been widely applied to study various fundamental properties of 2D materials, including the electron density of states, electron-electron interactions, band structure and quantum hall states. However, the concept of quantum capacitance has not yet been applied to electronic circuits. In this proposal, we will build high quality quantum capacitors based on 2D materials, including graphene, MoS2, and black phosphorus; Use gate voltage to electrically tune the capacitance value of 2D material quantum capacitors; Improve the structure of quantum capacitor to enhance the electrically tunable range of capacitance; Finally, we will apply the 2D material quantum capacitors to electronic resonant circuits to realize electrically tunable resonant frequency and achieve high quality factor.

量子电容是材料在外电势作用下电子填充费米能级所引起的自身充放电现象。不同于传统电容的概念，电子在费米能级的填充受制于泡利不相容原理等量子现象，因此被称为量子电容。此量子电容现象在二维材料中表现特别明显，被广泛用于二维材料的电子态密度、电子与电子相互作用、能带结构和量子霍尔态等基础科学研究。然而，二维材料量子电容器在电子电路中的应用研究仍是空白。本项目拟通过石墨烯、二硫化钼、黑磷等二维材料，构筑高质量量子电容器；利用外电势操纵量子电容器，实现电容大小的电致可调；优化其结构和性能，增强电容可调范围；最后将二维材料量子电容器应用在电子谐振电路中，实现谐振频率可调、高品质因子的电子电路。

量子电容现象广泛存在于具有低电子态密度的材料中，是电子填充费米能级引起的充放电现象，受制于泡利不相容等量子原理，是实现新型电调谐电容器件及电路的重要物理机制。二维材料具有低电子态密度、物性电致可调、硅基兼容性好等优势，是研究量子电容特性及电路应用的极佳平台。本项目基于石墨烯等二维材料，1）基于二维材料干法转移技术和光刻工艺，制备了“石墨烯/氮化硼/金属”等高质量平行板量子电容器件；2）在栅压作用下实现了器件电容的电调谐，在2V栅控电压下实现了电容值50%的改变，并提取了石墨烯量子电容与费米能的依赖关系，实验结果和理论计算数值取得了良好的一致性；3）基于石墨烯量子电容器构建了电子谐振电路，在2V栅控电压下实现了20%谐振频率的改变，电路品质因子可达65；4）通过进一步构建模型理论预测了石墨烯量子电容器的工作极限：在0.3V的超低栅控电压下可以实现700%的电容值调制与200%的谐振频率调制。本项目发展的石墨烯量子电容器相较于主流的微电子机械系统与半导体变容二极管具有占用面积小、功耗低、可调谐范围大的优势，为可调谐振电路的研究和应用提供了一个有希望的平台，对进一步提高芯片集成度具有重要促进和启示作用。