Molecular precursors to gallium oxide thin films

The donor-functionalised alkoxides [Et2Ga(OR)](2) (R = CH2CH2NMe2 (1), CH(CH2NMe2)(2) (2), CH2CH2OMe (3), CH(CH3)CH2NMe2 (4), C(CH3)(2)CH2OMe (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)(2)CH2OMe (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.