Study On Bonding Mechanism And Strain Behavior Of Silica/Graphene/Boron Nitride Structure Pressure Sensor

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.When the graphene/h-BN heterostructure is subjected to pressure,the electrical resistance will change significantly.This paper proposes a new type of pressure sensor structure,using graphene/h-BN heterostructure on Si/Si O₂ substrate as the pressure sensitive film,and the pressure cavity is designed as a prism shape.A layer of Si O₂ is deposited on the surface of the silicon substrate as an insulating layer to insulate the conductive Si from the heterostructure film as the substrate of the graphene/h-BN pressure sensor,and the pressure cavity is etched on this layer,graphene/h-BN heterostructure sensitive film is attached to the Si O₂ layer.When the sensitive film of the graphene/h-BN heterostructure is subjected to external pressure,the mechanical deformation will cause stress deformation,the heterostructure will have a piezoresistive effect,and the resistance value will change,which can be directly detected by the Wheatstone bridge The corresponding pressure value,and then the pressure sensor information is displayed through the computer and other equipment.The graphene/h-BN heterostructure pressure sensor is a MEMS sensor.First of all,this article uses molecular dynamics simulation to obtain the stress-strain relationship between graphene and graphene/h-BN heterostructure at the molecular atomic level.Taking the linear elastic part and fitting the elastic modulus value,it is found that the elastic modulus of single-layer graphene is about 907 GPa.As the number of graphene layers increases and the temperature increases,the elastic modulus value will decrease.Furthermore,the mechanical properties and temperature characteristics of the graphene/h-BN heterostructure are analyzed,and the elastic modulus of the heterostructure is 1343GPa,and the mechanical parameters of the heterostructure are less sensitive to temperature than graphene.Secondly,according to the density functional theory and the Material Studio software package CASTEP,the energy change during the bonding of graphene/h-BN heterostructures and the geometric optimization of three different configurations are analyzed,and the AB type(a carbon in nitrogen Above,the other is in the center of hexagonal boron nitride)is the optimal configuration,and the band gap opening is up to 3.803 e V.The band structure and density of states of this configuration are calculated.Finally,the finite element simulation analysis software ANSYS was used to study the pressure sensitive characteristics of pressure cavities of different shapes and different thicknesses of sensitive films of graphene/h-BN heterostructures.The results showed that the center deformation displacement of the rectangular prism cavity was the largest,and the sensor's The sensitivity is also higher.When the aspect ratio of the rectangular cavity is about 1.23,the pressure sensitivity of the pressure sensor is better,and the accuracy of measuring low pressure is higher.When the thickness of the heterostructure sensitive film is 20-40nm,the center deformation displacement decreases rapidly with the increase of the thickness of the heterostructure sensitive film,and the decrease is obvious,but when the thickness of the heterostructure sensitive film is greater than80nm,the change is relatively slow.These results provide a certain theoretical basis and basis for the design and manufacture of graphene/h-BN heterostructure pressure sensors.