Theory Study Of The Enfluence Of Dopants,Defects On The Sensing Behavior Of BP Gas

Monolayer of black phosphorus?BP?,also known as phosphene,is a newly emerging member of the two-dimensional?2D?material family.So far it has become the subject and focus of many scholars'research.As a new type of two-dimensional material,black phosphen appear particularly suitable for the application in nano-devices,energy storage and gas sensing.In addition,because black phosphorus itself has a"wrinkled"crystal structure,the specific surface area of BP is very large,which can be used for adsorption of various gases and sensing materials.Formaldehyde is one of the toxic gases and is easily volatile and carcinogenic.Therefore,it is very important to develop a simple and reliable sensor with strong adsorption capacity,high sensitivity for the detection of formaldehyde.In the paper,the CASTEP software package in Materials Studio based on density functional theory is used to explore the intrinsic,Al,Li,S atom doped BP systems and Al doped and undoped BP systems with P atom vacancy.The adsorption energy,density of states,band structure and charge transfer of formaldehyde on these systems were calculated,the influence mechanism of doping and defects or the coexistence of doping and defects on the sensing performance of BP systems was analyzed.The results show that the adsorption ability of BP to formaldehyde molecules is significantly enhanced after Al,Li doping.A deep impurity level is introduced in the?BP^Al+CH₂O?and?BP^Li+CH₂O?systems,and the system becomes a P-type semiconductor,which makes hole conduction favorable.The effective band gap is significantly narrowed after doping Al or Li,so the conductivity of both systems will become larger.It also shows that the doping of Al and Li improves the sensitivity of black phosphene.Therefore,Al or Li-doped BP is expected to become a new sensor material.There is no impurity level in the band gap in S-doped BP/formaldehyde system,and S-doping leads to no charge transfer between BP and formaldehyde molecules,the adsorption ability is very weak,so the S-doped BP system is insensitive to formaldehyde molecules.For non-doped Al BP systems containing P atom vacancy,studies have shown that non-doped Al BP systems containing P atom vacancies has a relatively weak ability to adsorb formaldehyde molecules and have no effect on electrical conductivity,so it is not suitable for use as sensors material.For the Al doped BP system with a P atom vacancy,the distance between formaldehyde molecule and BP system is significantly reduced,and the adsorption energy increase significantly compared to the values of the intrinsic BP.An impurity level is introduced in this system and the effective band gap is abviously narrowed,which indicates that Al doping improves the sensitivity of black phosphene containing P vacancy.Therefore,Al-doped BP containing P vacancy is expected to be a new sensor material.