| 摘要 |
PROBLEM TO BE SOLVED: To obtain thin coating having semiconductibility, excellent in coverability and suitable for the structural material for an electronic device by immersing an Al substrate into an aq. soln. contg. at least nitric acid ions and Al ions, applying a netative electric current to a counter electrode immersed into the aq. soln. and forming coating on the Al substrate. SOLUTION: The concn. of nitric acid ions in the aq. soln. to be used is preferably regulated to 0.01 to 0.5 mol/l. As the counter electrode, the one which does not change itself is usable, and particularly, platinum is preferable since it is stable also to the high concn. soln. of aluminum nitrate. The working voltage for applying a negative electric current to the counter electrode is different in accordance with the ion concn., pH, electric conductivity, temp. or the like of the aq. soln., but is ordinarily regulated to 3 to 4V. In the case the aluminum oxide thin coating formed in this way is used for electronic devices such as solar batteries, light is not uselessly absorbed, and light arriving at a photovoltaic layer can be maximized. |
