微机电系统压力传感器石墨烯/氮化硼膜片键合及应变行为

Bonding and strain behavior of graphene/boron nitride diaphragm of micro-electro-mechanical system pressure sensor

石墨烯和六方氮化硼(h-BN)层状材料的垂直堆叠组成的范德瓦尔斯异质结构,是制造高质量石墨烯器件的理想模型。我们提出了一种新型压力传感器的结构,在Si/SiO2衬底上用石墨烯/h-BN异质结构作为压力敏感薄膜。通过分子动力学模拟的方法,从分子原子层面得到了石墨烯和石墨烯/h-BN异质结构的应力-应变关系,发现单层石墨烯的弹性模量约为907 GPa,随着温度的升高,弹性模量数值会变小。进而分析了石墨烯/h-BN异质结构的力学特性和温度特性,得出异质结构的弹性模量为1 343 GPa,异质结构的力学参数对温度的敏感性比石墨烯低。其次,根据密度泛函理论和CASTEP分析了石墨烯/h-BN异质结构键合时的能量变化以及三种不同构型的几何优化,得出AB型(一个碳在氮上,另一个在六方氮化硼的中心)为最优构型,带隙打开最大为3.803 eV。计算得到了此构型的能带结构与态密度。这些结果为石墨烯/h-BN异质结构压力传感器的设计与制作提供了一定的理论基础与依据。

The van der Waals heterostructure composed of a vertical stack of graphene and hexagonal boron nitride(h-BN) layered materials is an ideal model for manufacturing high-quality graphene devices. A new type of pressure sensor structure was proposed, using graphene/h-BN heterostructure on Si/SiO2 substrate as a pressure sensitive film. Through the method of molecular dynamics simulation, the stress-strain relationship between graphene and graphene/h-BN heterostructure was obtained from the molecular atomic level. It is found that the elastic modulus of single-layer graphene is about 907 GPa, and as the temperature increasing higher, the elastic modulus value will become smaller. Furthermore, the mechanical properties and temperature characteristics of the graphene/h-BN heterostructure were analyzed, and the elastic modulus of the heterostructure is 1 343 GPa. The mechanical parameters of the heterostructure are less sensitive to temperature than graphene. Secondly, according to density functional theory and CASTEP, the energy change of graphene/h-BN heterostructure bonding and the geometric optimization of three different configurations were analyzed, and the AB type(One carbon is on the nitrogen, the other is on the center of hexagonal boron nitride) is the optimal configuration, and the maximum band gap opening is 3.803 eV. The band structure and density of states of this configuration were calculated. These results provide a certain theoretical basis and basis for the design and manufacture of graphene/h-BN heterostructure pressure sensors.