Molecular precursors to gallium oxide thin films

Abstract

The donor-functionalised alkoxides [Et₂Ga(OR)]₂ (R = CH₂CH₂NMe₂ (1), CH(CH₂NMe₂)₂ (2), CH₂CH₂OMe (3), CH(CH₃)CH₂NMe₂ (4), C(CH₃)₂CH₂OMe (5)) were synthesised by the 1∶1 reaction of Et₃Ga with ROH in hexane or dichloromethane at room temperature. Reaction of Et₃Ga with excess ROH in refluxing toluene resulted in the isolation of a 1∶1 mixture of [Et₂Ga(OR)]₂ and the ethylgallium bisalkoxide [EtGa(OR)₂] (R = CH₂CH₂NMe₂ (6) or CH(CH₃)CH₂NMe₂ (7)). X-ray crystallography showed that compound 6 is monomeric and this complex represents the first structurally characterised monomeric gallium bisalkoxide. Homoleptic gallium trisalkoxides [Ga(OR)₃]₂ were prepared by the 1∶6 reaction of [Ga(NMe₂)₃]₂ with ROH (R = CH₂CH₂NMe₂ (8), CH(CH₃)CH₂NMe₂ (9), C(CH₃)₂CH₂OMe (10)). The decomposition of compounds 1, 4, 5 and 8 were studied by thermal gravimetric analysis. Low pressure CVD of 1 and 5 resulted in the formation of thin films of crystalline Ga₂O₃.