Zinc precursor synthesis and the aerosol assisted chemical vapour deposition of zinc oxide thin films

This thesis describes the synthesis of novel zinc complexes formed from the reaction of diethylzinc (ZnEt2) and a range of dicarbonyl and β-iminoester ligands. These complexes, as well as zinc triflate, [Zn(OTf)2] were successfully employed as precursors in the aerosol assisted chemical vapour deposition (AACVD) of zinc oxide (ZnO) and aluminium doped ZnO (AZO) thin films. Films of this type are of significant interest for a number of applications, including as transparent conducting oxide (TCO) materials. Investigations into the reactions between ZnEt2 and dicarbonyl compounds led to the successful synthesis, isolation and characterisation of trimeric zinc oxane complexes [(Zn(Et)(OC(R)CHC(Me)O))3] with a central six membered Zn3O3 ring, where R = OMe (1), Me (2), OEt (3) and OtBu (4). Controlled oxygenation reactions of solutions of (1) - (4) also lead to the successful synthesis of zinc oxane clusters [(Zn(OC(R)CHC(Me)O)2Zn(Et)OEt)2], where R = OMe (5), Me (6), OEt (7) and OtBu (8). Zinc β-iminoesterate complexes with increased functionality have also been synthesised in reactions between ZnEt2 and the synthesised β-iminoester ligands MeC(NHR)CHC(O)OEt, where R is iPr (L1), Me (L2), iBu (L3) and (CH2)2iPr (L4). Homoleptic zinc β-iminoesterates [Zn(OC(OEt)CHC(Me)NR)2] (9) - (12) were synthesised in 1:2 equivalence reactions between ZnEt2 and (L1) - (L4) respectively. Heteroleptic dimeric complexes [(Zn(OC(OEt)CHC(Me)NiPr)(Et))2] (13) and [(Zn(OC(OEt)CHC(Me)N(CH2)2iPr)(Et))2] (14) were synthesised in 1:1 reactions of ZnEt2 and (L1) and (L4) respectively. Thermal decomposition and AACVD studies were performed using [Zn(OTf)2] and zinc complexes (6), (9) and (10) leading to the successful deposition of ZnO and AZO thin films. Films deposited from (6) and (10) required annealing to remove significant carbon content but the change in identity of the organic substituent between (10) and (9) in the β-iminoesterate system was found to greatly reduce the carbon in the films. [Zn(OTf)2] and complex (9) were both determined to be highly suitable AACVD precursors for the deposition of doped and undoped ZnO thin films.