Anodic oxidation has been employed as an useful corrosion resistant protective surface modification for chambers and inner parts made of aluminum alloys in manufacturing equipment such as plasma CVD and etching systems. Developing series of anodic aluminum-alloy oxide (A Al-A O) films(1-3) we had noticed the unexplained difference among infrared spectra of samples with wide range of thicknesses keeping other parameters same. To clarify this phenomenon we have examined thickness dependence of A Al-A O films by Fourier transform infrared (FT-IR) microspectroscopy precisely and will report here.
Sample preparation: We prepared A Al-A O film(s) of 1-35 micrometer in thickness on A1100, A5052, and A6061 alloy in an oxalic acid bath and a sulfuric acid bath, sealed them at various conditions. Some of the thick A Al-A O films were cut obliquely by a grinder at the inclination 1/200 for depth-profiling purpose.
Characterization: Samples were observed by mainly FT-IR microspectroscopy and also characterized by optical microscopy, scanning electron microscopy, acid-dissolution examination, admittance measurements and electron probe X-ray microanalysis.
Results: Since A Al-A O films are transparent in the infrared wavelength range, all the information along the film thickness should be included in a measured reflection-spectra. In the midst of pore growth the structure of A Al-A O film changed chemically keeping the nearly straight pores form at about several micrometer depending on preparation condition. Examined samples were more than 100 cases and the same thing was observed in all the combinations of alloys and acids. The resultant thick A Al-A O films are chemically in layered structure. More precise cross-sectional observation and compositional analysis are necessary.
(1) H.Sato, H.Nakamura, S.Tsukahara, Y.Ishikawa, S.Misawa, Y.Takahashi, and S.S.Inayoshi:
JVSJ, 45 (2002) 438.
(2) T.Tsujita, H.Sato, S.Tsukahara,Y.Ishikawa:JVSJ, 48 (2005) 217-219.
(3) S.Tsukahara, Y.Takahashi, H.Sato, T.Tsujita, H.Nakamura, and Y.Ishikawa:presented
at annual meeting of VSJ on Nov.11, 2005.
|