Theoretical Design And Performance Study Of New Two-dimensional Phosphorus-containing Sensor Material

Sensors can measure specific objects and produce electrical signal,which include mechanical sensors and gas sensors.Mechanical sensors can be used as wearable devices for human activity and health monitoring.The key properties of sensing materials require excellent sensitivity for stress,low power consumption and flexibility.Gas sensors can be used to monitor environmental harmful gases.The key properties of gas sensing materials require excellent sensitivity,selectivity,environmental stability,short recovery time and reversibility.The relative researches of sensor materials are significant to promote the development of advanced electronic devices and industrial safety activity for our country.Two-dimensional materials are the star materials in the field of novel functional electronic devices.Due to the quantum confinement effect,two-dimensional materials exhibit significantly different physical and chemical properties than bulk materials.Additionally,two-dimensional materials usually possess a larger specific surface area,more abundant adsorption sites,and more flexible electronic structure than three-dimensional materials.As a consequence,designing new two-dimensional materials and exploring their performance become a research hot in the scientific research.Recently,many functional semiconducting two-dimensional materials have been theoretically predicted and experimentally synthesized.Among them,Dirac materials and phosphorus-semiconductor materials exhibit excellent carrier mobility and potential application in sensing materials.Thanks to algorithmic developments as well as increases in computer power,theoretical simulations have become a cheap and efficient research tool for two-dimensional materials designing.Until now,much two-dimensional sensing materials were predicted theoretically and were verified via experimental synthesis.Notably,performance of two-dimensional sensing materials is determined by the response ability to stress/gas through the structural and electronic structural interactions.The current-voltage（I-V）curves,can be calculated via the non-equilibrium Green’s function simulations,can be used to directly evaluate the performance of the two-dimensional sensors.Moreover,the new two-dimensional functional devices can be effectively achieved by hydrogenation,halogenation,atomic doping,element substitution,stress-strain,etc.In this work,the first-principles calculations were carried out to study two new two-dimensional phosphorus-containing materials as sensing materials.The details and main conclusions are summarized as:1.Dirac materials are named by its special Dirac state in the band structure,of which graphene is a typical representative.In the vicinity of the Dirac cone,the energy bands exhibit a linear scattering relationship,hence the effective mass of electron is close to zero,which induce ultrahigh carrier mobility（～10⁵m/s）.Since the discovery of graphene,series Dirac materials were proposed through theoretical calculations and experimental synthesis,such as silicene and borophene.However,the Dirac materials are still rare,and researchers have not yet proposed an effective method to construct new Dirac materials.Meanwhile,as a mechanical sensing material,graphene possesses a large elastic modulus（340 N/m）,and modulating Dirac cones requires a very large strain（≤26.5%in-plane strain or≤12%shear strain）due to the symmetry protection;herein,a certain stress would difficultly induce a large electronic structural change,resulting in a low sensitivity to stress.Accordingly,this work proposes an effective strategy to construct Dirac materials based on electronic counting rules,and a series of Dirac materials ABX₃（where A=F,Cl,Br,or I;B=P and As;X=C and Si）were proposed.First-principles calculation results show that 14 kinds of ABX₃ monolayer exhibit good stability and high Fermi velocity.Interestingly,due to the strong electron interaction between the A-B unit and the C₆ ring,the FPC₃,Cl PC₃,Br PC₃,and FAs C₃monolayer exhibit intrinsic n-type self-doping Dirac cones,which is beneficial for achieving high-speed carriers.Interestingly,a relatively small in-plane biaxial strain（-5%）of Cl PSi₃ monolayer can induce self-doping effects for Dirac cone.Herein,the Cl PSi₃ monolayer has a remarkable response to stress.The calculated current-voltage（I-V）curves reveal that the response strength of Cl PSi₃ monolayer to-5%stress is 11.57times than that of a graphene-based mechanical sensor at a bias voltage of 1.10 V,indicating that the Cl PSi₃ monolayer is a potential excellent mechanical sensor.2.Black phosphorene is a typical semiconductor material with high carrier mobility,which has been demonstrated to be an excellent gas sensing material in both experimental and theoretical techniques.However,the poor stability and poor gas selectivity under ambient conditions limit the practical applications of black phosphorene.Recently,penta-BeP₂ monolayer has been reported with good structural stability and moderate bandgap,exhibiting potential high-performance gas sensing properties.However,the gas sensitivity,response ability,environmental oxidation resistance,gas selectivity and recovery time still need to be explored.In this work,the gas sensing performance of penta-BeP₂ monolayer for toxic gases was investigated using first-principles calculations.The results show that penta-BeP₂ monolayer chemically adsorbs toxic gases,including CO,NH₃,NO,and NO₂,accompanied with significant charge transfer（-0.182 to 1.129 e）,but form weak Van der Waals interaction with ambient gases,including H₂,N₂,H₂O,O₂,and CO₂,indicating good gas sensing selectivity and ambient stability.The calculated I-V curves reveal that penta-BeP₂monolayer is sensitivity to toxic gases under ambient condition.At a bias voltage of 0.7V,the response sensitivities of penta-BeP₂ monolayer to toxic gases CO,NH₃,NO,and NO₂ were up to 9.23,13.48,31.10,and 128.90,respectively,is much larger than traditional metal oxidation gas sensors.Furthermore,the adsorption energy of penta-BeP₂ monolayer with all toxic gases is in a moderate range（～1.00 e V）,which not only guarantees good response capability but also reversibility at room temperature.Consequently,the calculation results in our work demonstrate that penta-BeP₂monolayer possesses excellent selectivity,sensitivity,and reversibility as a new toxic gas sensing material.