Study On Surface Modification Of Two-dimensional GaN-based Materials And Preparation Of GaN Nanosheets

Owing to the wide band gap,excellent photoelectric properties and good thermodynamic stability,two-dimensional(2D)GaN has a broad application prospect in optoelectronic devices,spin semiconductor devices,gas sensor components and high power devices,etc.At present,2D GaN is a hotspot in the field of 2D materials research.Based on first principles,the electronic and optical properties of g-GaN/C60 heterojunctions and CO,H2S and NO adsorbed on alkali metals Li,Na,K,Rb and Cs doped g-GaN monolayer have been investigated.GaN nanosheets were prepared by Chemical vapor deposition.The main research content and result are as follows:Firstly,g-GaN/C60 heterojunction belongs to Type-II structure,the CBM and VBM is dominated by the 2p orbital of C atoms in C60 molecule and the 2p orbital of N atoms and 3d orbital of Ga atoms in g-GaN monolayer respectively,built-in electric field up to 6.11eV,and can effective separation of electrons and holes,and extend carrier lifetime.When the vertical electric field of 0.2 and 0.4 V/A is applied,the Type-II structure characteristic is still retained,and with the increase of electric field intensity,the charge transfer quantity increases,and the separation efficiency of charge carriers is improved.The absorption coefficient shows that g-GaN/C60 heterojunction has obvious absorption peaks in both ultraviolet and visible region,which makes g-GaN/C60 heterojunction have broad application prospects in the field of optoelectronic devices,for example for solar cells.Secondly,based on first principles,the toxic gas molecules CO,H2S and NO adsorbed on intrinsic g-GaN monolayer,the alkali metals Li,Na,K,Rb and Cs doped g-GaN monolayer and the CO,H2S and NO adsorbed on alkali metals(Li,Na,K,Rb and Cs)doped g-GaN monolayer were studied,respectively.The magnetic properties of NO adsorbed on intrinsic g-GaN monolayer were observed but were not observed in the CO and H2S adsorbed systems.However,the magnetic properties of the three adsorbed systems were observed after the doping of alkali metals.The hybridization of orbitals is caused by the doping of alkali metals,and there are hybridized orbital in forbidden band,which is beneficial to the transition of valence band electrons and improve the electrical conductivity of the adsorbed system.The charge transfer of the adsorption system occurs between gas molecules,Ga atoms,N atoms and doped atoms,indicating that doping can significantly improve the adsorption properties of 2D GaN-based materials,thus promoting the application of 2D GaN-based materials in gas sensor.Thirdly,chemical vapor deposition(CVD)method was used to explore the GaN nanosheet with good morphology by controlling the reaction time,reaction temperature rate and ammonia flow,with the molten gallium as the gallium source,NH3 as the nitrogen source and double tungsten sheets are used as the substrate,the lower layer tungsten is coated with gallium metal,and the upper layer tungsten is placed above the lower layer,the controllable growth of GaN nanosheets with uniform density and thin thickness was studied.Under the conditions of ammonia flow rate of 100sccm and temperature interval of 750-800?,hexagonal wurtzite GaN nanosheets with good crystallinity were prepared by a controlled manner,the thickness is less than 100nm and the transverse size is 1-2?m,and the research results are of great significance to advance the application of two-dimensional GaN.