First-principles Study On Magnetic Properties Of Two-Dimensional ZnS Doped With Nonmetal Elements And Novel Heterostructure Photocatalytic Performance

The dilute magnetic semiconductor is a new kind of functional material widely used in spintronics field.Nevertheless,most of semiconductor materials in nature exhibit the non-magnetic ground state,which limits their applications in electronic devices.However,dilute magnetic semiconductors can be prepared by doping 3d and 4f transition metal elements or rare-earth elements instead of non-magnetic cations,which can combine information storage and processing by the spin properties of magnetic materials.Compared with traditional semiconductor materials,dilute magnetic semiconductor materials can process information faster,consume less power,and store information much safer.Therefore,it is of great significance to study dilute magnetic semiconductor materials.Semiconductor photocatalysts can decompose water to produce hydrogen under visible light irradiation,which may effectively alleviate the current energy shortage and environmental pollution problems.Although many photocatalysts have been synthesized experimentally and investigated theoretically,they also have low efficiency in photocatalysis water splitting and possess a narrow visible-light absorption range.At present,constructing heterostructure photocatalyst,attracted widely attention,is a potential method to improve the photocatalytic performance.Compared with ordinary photocatalysts,two-dimensional（2D）semiconductor heterostructure photocatalysts have better photocatalytic properties,such as higher carrier mobility,effective electron-hole pair separation,and stronger visible light absorption capacity.For example,2D semiconductor heterostructure photocatalysts,such as g-C₃N₄/MoS₂,g-C₃N₄/InSe,TiO₂/CdS and so on,present better photocatalytic performance than their individual catalyst.In present work,the magnetic and optical properties of 2D ZnS doped with nonmetallic materials were systematically studied using first-principles calculations.Further,we also methodically explored electronic structure and photocatalytic mechanism of the new 2D Zr₂CO₂/InS and MoS₂/InTe heterostructure.The main research contents are summarized as follows.The eigenstate of 2D ZnS is a stable non-magnetic ground state,and the doping of Nonmetal atom,C,N,P and As,successfully induce magnetism.The main contribution of magnetism is from the spin magnetic moment that it is generated by outermost electrons provided by the doped atoms.The stable structure of the C and N doping system exhibits ferromagnetism,while the P and As doping system shows antiferromagnetism.The doping of non-metal atomes for single-layer ZnS causes the blue-shift of absorption peak in the high-energy region,meanwhile a new absorption peak is generated in the low energy region,enhancing the absorption ability of 2D ZnS in the low-energy infrared waves.The results show that the non-metal atoms doped two dimensional ZnS can be suggested as a promising dilute magnetic semiconductor,which has a broad application in the field of spintronics and optics.The novel 2D Zr₂CO₂/InS heterostructure is a direct band-gap semiconductor with a lattice mismatch of less than 3%and formation energy of-0.49 eV.This result indicates that the heterostructure presents a stable structure.The gap value of Zr₂CO₂/InS is 1.96 eV along with a wide visible-light absorption range,and the absorption coefficient is up to 10⁵cm^-1.Heterostructure reveals a type-Ⅱband structure.The valence band offset and conduction band offset are 1.24 and 0.17 eV,respectively.The photo-generated electrons are transferred from the Zr₂CO₂ layer to the InS layer with holes migrating opposite,which achieves effective separation of electrons and holes.Moreover,InS is a indirect band gap semiconductor,which can further reduce the recombination of electron-hole pairs.In summary,the new two-dimensional Zr₂CO₂/InS heterostructure is a favorable visible-light photocatalyst.Two dimensional MoS₂/InTe heterostructure is a band-gap semiconductor material with a lattice mismatch of less than 1%and formation energy of-1.64 eV,indicating the stability of heterostructure.The band gap of the MoS₂/InTe heterostructure is 2.01 eV.The conduction band minimum is 0.32 eV lower than the reduction potential of water,and valence band maximum is 0.64 eV higher than the oxidation potential of water.It has great light harvesting capacity in the visible light region,effectively improving the power conversion efficiency.Besides,MoS₂/InTe heterostructure exhibits a is type-Ⅱband alignment.The band offset effectively promotes separation of the electrons and holes,which reduces the recombination of that.Therefore,the heterostructure of MoS₂/InTe is an effective potential visible-light photocatalyst,which can provide guidance for the theoretical and experimental designing the promising photocatalyst in the future.