ORDER-DISORDER TRANSITIONS OF YTTRIUM ARACHIDATE LANGMUIR-BLODGETT-FILMS VIA ELLIPSOMETRIC ANISOTROPIES

Ellipsometric order-disorder transition studies have been performed on films of yttrium arachidate. Upon heating, the films were observed to undergo two optical transitions at 65-degrees-C and 100-degrees-C. At room temperature, the as-deposited films were found to be anisotropic, with indices of refraction of N(x) = 1.503 +/- 0.004 and N(z) = 1.554 +/- 0.004 and a layer spacing of 2.73 +/- 0.03 nm. Above 100-degrees-C the films were isotropic, with N = 1.440 +/- 0.004 and a thickness of 3.13 +/- 0.03 nm per original layer. Between 65-degrees-C and 100-degrees-C the films showed unusual behaviour. X-Ray diffraction showed that the film maintains a strong layered structure when cooled from below 100-degrees-C. When cooled from above 100-degrees-C, X-ray peaks are greatly reduced. The films showed no desorption below 100-degrees-C.