Electronic Transport Regulation And Gas Sensors Design Of Novel Low Dimensional Nanomaterials

In the post-Moore’s Law era,the existing microelectronics processing technology has approached its limits.As the device size continues to shrink,the traditional silicon material is severely affected by quantum tunneling,which affects the performance of transistors in turn.Recently,atomic-level thick two-dimensional materials have exhibited numerous novel physical phenomena,such as spin separation,anisotropic transport,negative differential resistance curve,and rectification effect,because of its rich properties and ultra-thin characteristics,providing new directions and design ideas for constructing high-performance devices in the semiconductor and device materials field.This paper adopts a first-principles calculation method combining density functional theory with non-equilibrium Green’s function,with the calculation based on several target 2D materials with adjustable bandgap,fast electron migration speed,and excellent dynamic stability and process compatibility.This study focuses on the calculation of the transport properties of low-dimensional nanoscale devices and further designs for high-performance gas sensors applied in precision environments by considering the electron coupling between molecules and interfaces.The research content and conclusions are divided into the following parts:（1）Low-dimensional gallium nitride（Ga N）and its nanoderivatives are promising materials for the future development of microelectronic devices.Among the five stacking configurations of the two-dimensional bilayer Ga N nanosheets,the AA-NN（Ga Ga）configuration is the most stable and the stacking arrangement does not change the bilayer Ga N’s indirect bandgap.One-dimensional nanodevices based on bilayer Ga N exhibit Kirchhoff’s current law,similar to parallel circuits.The armchair-edged nanoribbon devices display a width effect which significantly affects the current-voltage curves and transport properties of the device due to the bandwidth of the nanoribbon.（2）In electrical transport calculations,the effect of material surface defects is often taken into consideration.Tungsten ditelluride（WTe₂）is a material with excellent electromagnetic tunability.Through vacancy defects,2H-V^Wchanges from a semiconductor to a semi-metal,while 2H-V^Teand 2H-V^2Techange from a direct bandgap to an indirect one.In addition,W or Te atoms in WTe₂can be replaced by Al,B,C,Co,Fe,N,P,and Si atoms.Although these doping atoms have not caused any spin polarization phenomenon in the Td phase,all 2H-phase doping systems except for group IV elements exhibit spin polarization and transform into magnetic semiconductors.（3）The electronic structure of the intrinsic g-C₄N₃/Mo S₂Van der Waals heterojunction shows the ferromagnetic half-metallicity and superior adsorption capacity for gas molecules.The two-dimensional g-C₄N₃/Mo S₂-based nanodevices have perfect single spin conduction behavior with close to 100%spin separation efficiency,negative differential resistance effect and other strange electron transport phenomena.In addition,g-C₄N₃/Mo S₂exhibits directional dependency and strong transport anisotropic behavior under bias windows,while the g-C₄N₃/Mo S₂based gas sensor is more sensitive to chemisorbed CO,NO,NO₂and NH₃molecules.The maximum gas sensitivity of NO can reach 6.45 at 0.8 V.（4）The two-dimensional Janus material Pd₂P₂Se X（X=O,S,Te）crystallised into an orthogonal lattice with the shape of a pentagon fold.Its stability was verified by phonon spectra and their indirect band gaps of 0.56,1.02,0.84 e V were shown after considering spin orbit coupling.The PIN device based on Pd₂P₂Se X has obvious controllability of grid voltage.Under biaxial strain regulation,the band gap of the central scattering region decreases and the current density of the two-dimensional device is greatly enhanced.The switching effect of the circuit is realized and the switching ratio reaches 1.44×10⁸.In addition,Pd₂P₂Se X-based PIN junction devices have interface adsorption and electronic coupling with NO and NO₂to achieve the transformation of semiconductor to metal properties,especially the recovery time of Pd₂P₂Se O to NO recovery time is 49.01 seconds,and that of Pd₂P₂Se S to NO₂is 23.80 seconds.NO and NO₂gas molecules can be detected effectively.