Synthesis of homoleptic gallium alkoxide complexes and the chemical vapor deposition of gallium oxide films

A general synthetic route to gallium alkoxide complexes involving reactions of gallium tris(dimethylamide) with alcohols was developed and gallium oxi de films were prepared by using a gallium alkoxide complex as the precursor in a chemical vapor deposition process. The complex [Ga(NMe2)(3)](2) react ed with i-BuOH and i-PrOH to yield the tetramers Ga[mu -OR)(2)Ga(OR)(2)](3) where R = i-Bu and i-Pr, respectively. Consistent with previous observatio ns, the solution equilibrium Ga[mu -O-i-Pr)(2)Ga(O-i-Pr)(2)](3) reversible arrow 2[Ga(mu -O-i-Pr)(O-i-Pr)(2)](2) was observed (DeltaH degrees = 8.7(0. 4) kcal/mol, DeltaS degrees = 27(1) eu, and DeltaG degrees (298) = 0.63(0.0 4) kcal/mol). For the less sterically crowded tetramer Ga[(mu -O-i-Bu)(2)Ga (O-i-Bu)(2)](3), there was no evidence for a tetramer-dimer equilibrium. In contrast to the results obtained using i-BuOH and i-PrOH, the bulkier alco hols t-BuOH and EtMe2COH reacted with [Ga(NMe2)(3)](2) at room temperature to yield mixtures of the dimer [Ga(mu -OR)(OR)(2)](2) and the amine adduct Ga(OR)(3)(HNMe2), while i-PrMe2COH and Et2MeCOH reacted to produce Ga(OR)(3 )(HNMe2) compounds exclusively. Upon heating in an open system, the amine c ould be removed from the Ga(OR)(3)(HNMe2) compounds to yield the correspond ing homoleptic alkoxide dimers. Low-pressure chemical vapor deposition usin g [Ga(mu -O-t-Bu)(O-t-Bu)(2)](2) and O-2 precursors gave Ga2O3 films at sub strate temperatures of 300-700 degreesC. The as-deposited films were carbon -free, amorphous, and highly transparent in the 350-800-nm region.