Study On Reaction Mechanism Of Al₂O₃ And Al₂S₃

As a preparation technology of nanomaterials,atomic layer deposition(ALD)has widely been applied in the fields of microelectronics,optics,energy and catalysis.Essentially,ALD is a special chemical vapor deposition(CVD)technology,which is generally composed of two half-reactions.ALD has unique advantages,such as excellent conformity,large-area uniformity and precise control of submonolayer film thickness.Therefore,it can prepare various materials,such as oxides,nitrides,sulfides,metals and organic-inorganic hybrid materials.In recent years,Al2O3 ALD-is the research model system.The reaction mechanisms of Al2O3 ALD have been widely studied.This paper summarizes these theoretical advances on the reaction mechanisms of Al2O3 ALD.At present,ALD has been used to prepare the metal sulfides such as Al2S3 and Li2S,which has many applications in lithium ion batteries and solid electrolytes.This paper studies the mechanism of trimethylaluminum(TMA)and H2S half-reactions in Al2S3 ALD via density functional theory(DFT)calculations.The results show that TMA can react with surface sulfhydryl groups to eliminate methyl group via the four-membered ring(4MR)transition state.As the temperature increases,the elimination of methyl groups requires more energy.H2S can react with surface methyl groups to generate methane.The additional H2S molecules and reaction cites orientation have little effect on the transition state of the four-membered ring.It is unfavorable for H2S to participate the reaction through the six-membered ring(6MR)transition state.Surface methyl groups and sulfhydryl groups can further react with adjacent sulfhydryl groups on the surface to release CH4 and H2S.Recently,aminoaluminums can be used as a metal source precursor for Al2S3 ALD.In this paper,three precursors of triaminoaluminum(TAA),trimethylaminoaluminum(TMAA)and trisdimethylaminoaluminum(TDMAA)are designed by introducing amino groups.The adsorption and dissociation mechanisms of three aminoaluminums on Al2S3 surface were studied by DFT calculation.The calculation results show that the aluminum precursor containing amino groups will play a catalytic role in the reaction,which is more active than the aluminum precursor containing alkyl groups,and the different amino functional groups also have different reactivity.