The liquid compound pentamethylcyclopentadienyl gallium (GaCp*) exhibits several notable characteristics, including a relatively high vapor pressure and thermal stability up to 250 °C. Using it as a precursor, Ga2O3 thin films can be deposited by atomic layer deposition (ALD), with the combination of oxidants of H2O followed by O2 plasma (WpO), where H2O is used to desorb the ligand, and O2 plasma then oxidizes the surface Ga species. A self-limiting surface reaction during the ABC-type ALD process applying GaCp*, H2O, and O2 plasma in order was observed with no delay in nucleation for pulse times for GaCp*, H2O, and O2 plasma of 0.1, 3.0, and 50 s, respectively, at a growth temperature of 200 °C. The growth rate was 0.06 nm/cycle. ALD-Ga2O3 deposition was possible even if only O2 plasma was used as an oxidant, though it takes a very long time for the oxidation by O2 plasma to reach saturation. On the other hand, when no O2 plasma was used, no film could be deposited using H2O and O2 in any combination. Ga2O3 films deposited by ALD using the WpO oxidant exhibited a stoichiometric O/Ga ratio of 1.5, with negligible residual carbon and an amorphous structure. These results show that GaCp* is a promising candidate precursor for forming high quality Ga2O3 films.
Anodic films were formed on aluminum at 0.5 A dm−2 to 50 V in a 1 mol dm−3 triethylmethylammonium hydrogen maleate/γ‐butyrolactone solution of varying water content (10 to 1000 ppm). The resultant films were characterized by transmission electron microscopy, Auger electron spectroscopy, Fourier transform infrared spectroscopy, and x‐ray absorption near edge structure analysis. The thickness, chemical composition, and structure of the resultant barrier‐type films were affected markedly by water content with the incorporation of electrolyte components into the anodic films enhanced by decreasing water content. The film formed below 200 ppm of water proved to be an electropolymerized organic film containing a small amount of aluminum, while the film formed above 700 ppm of water was a different aluminum oxide containing a small amount of carbon. In the transition region between 200 and 700 ppm of water, a laminated composite film of high carbon content in the outer layer was produced. All the films showed a new infrared peak at 1610 cm−1, which did not change upon annealing at 300°C. This peak was assigned to an Al=O stretching vibration. The permittivity of the films was lowered by incorporation of organic substances into the film material.
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