Takahiro Imai

Enhancement of the deposition rate of TiO2 film in radio frequency reactive sputtering

Titanium oxide thin films were prepared using rf reactive sputtering in which a titanium target was sputtered in a mixture of Ar and reactive O2 gas. The flow modulation of reactive gas was proposed to enhance the deposition rate of the film which is generally low in continuous flow reactive sputtering. The experimental results indicated that the deposition rate could be enhanced maintaining the film stoichiometric ratio of TiO2. The enhancement occurred because the modulated flow appeared to reduce the formation of compounds on the target surface which inhibit sputtering under continuous flow conditions. The effects of the flow modulation were understood by adapting a reactive sputtering theoretical model.

Computational modeling of reactive gas modulation in radio frequency reactive sputtering

Computer simulation of reactive sputtering was carried out to explain the enhancement of the deposition rate of complete oxide film using reactive gas flow modulation. The model dealt with the preparation of TiO2 film with a titanium target and oxygen in rf reactive sputtering. The computed results showed good agreements with the experimental data obtained in our previous work. The effects of the flow modulation were elucidated with the calculated timewise variations for partial oxygen pressure and target coverage. The effects of modulation patterns were also evaluated using the simulation.

Room-temperature plasma enhanced atomic layer deposition of aluminum silicate and its application in dye-sensitized solar cells

The authors present a plasma enhanced room-temperature atomic layer deposition (ALD) technique for depositing aluminum silicate on TiO2 photoanodes for dye-sensitized solar cells. In the ALD process, adsorption of the precursor is completed in a two-step process involving sequential application of a subsaturation quantity of tris(dimethylamino)silane (TDMAS) and an Al precursor trimethylaluminum to the target surface. The Al-to-Si atomic ratio is controlled by the initial coverage of TDMAS on the sample surface. Aluminum-silicate coatings with a balanced composition of Al and Si are applied to the TiO2 nanoparticle photoanodes in N719-based dye-sensitized solar cells. A one-cycle ALD coating improves the short circuit current density, suggesting the enhancement of N719 dye adsorption or charge separation at the interface of the dye and TiO2 photoanode. Electro-impedance analysis suggests that the improved power generation does not correlate with the charge recombination of electrons in TiO2 and I3− ions i...