PREPARATION OF TRANSPARENT ALUMINA FILMS BY THE SOL-GEL PROCESS AND ITS APPLICATION TO PHOTO-FUNCTIONAL FILMS

We have examined the presentation of transparent alumina film and semi conductor microcrystalline- or organic dye-doped alumina film prepared by the sol-gel process using aqueous sol starting from AlCl3 . 6H2O. The resulting non-doped alumina film obtained by sol-gel transformatio n is transparent in the visible and near infrared, even heated up to 1 000-degrees-C. From XRD and Al-27 MAS NMR results, it appears that the transitions of the alumina are as follows: 25-300-degrees-C, amorphou s; 400-1000-degrees-C, a kind of gamma(gamma, delta, etc.); above 1000 -degrees-C, alpha. Alumina films doped with laser dyes (rhodamine 6G ( R6G), rhodamine B (RB), sulforhodamine 101 (SR 101), coumarin 1 (Cl) a nd 2-(1-naphthyl)-5-phenyl oxazole (alpha-NPO)) and laser dye pairs (R 6G-RB, Cl-uranin and diphenyl oxazole-alpha-NPO) have exhibited laser emission and energy-transfer-type emission by nitrogen laser pumping, respectively. The maximum conversion efficiency is 2.1% (for R6G). Abs orption spectra of films doped with hole-burning dyes (5,8-dihydroxy-1 ,4-naphthoquinone, resorufin and alpha,beta,gamma,delta-tetrakis (4-su lfophenyl) porphine (TPPS)) have been burned on irradiation by laser. The hole spectrum of TPPS-doped film was observed even at 60 K. Film d oped with nonlinear optical dye (2-methyl-4-nitroaniline) has exhibite d the second harmonic wave laser by irradiation with an Nd:glass laser (lambda = 1064 nm) as a fundamental. CdS-doped film showed relatively sharp blue-shifted absorption attributed to the size quantization eff ect compared with bulk CdS. Large non-linear absorption and refractive index have been observed, because high concentration of CdS particles can be achieved by using this method.