| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
The photoelectrochemical etching (photoetching) of a TiO_2 electrode in sulfuric acid solution generates nano-structured surface (named "nano-honeycomb" structure). Another interesting finding is its potential dependent etching site selectivity, i.e., a preferential photoelectrochemical dissolution of grain bulk for a sintered pellet TiO_2 electrode under weak anodic polarization (upward band bending), which results in the formation of a "skeleton" structure consisting of only grain boundaries. The latter must offer a possibility of characterize grain boundaries, which are known to play a crucial role in some ceramic devices.
In the present work, we report more detailed characterization of grain boundary of a sintered pellet TiO_2 as well as the size control of the "nano-honeycomb". Varying the photoetching conditions such as photoetching time, photoetching potential and light intensity did not change the size of a "nano-honeycomb", suggesting that its size is a reflection of the intrinsic property of the TiO_2 used. Modifying the properties of TiO_2 would change it. Actually upon increasing the donor density of a TiO_2 electrode by reducing it in H_2 atmosphere, the size of the "nano-honeycomb" decreased. For a TiO_2 electrode with a donor density of the order of 10^<21> cm^<-3>, the size amounts to 30 nm. The formation of such a fine structure will find useful applications to various devices such as (photo) catalysts, sensors and dye-sensitized solar cells.
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