MEDIUM-ENERGY ION-BEAM ANALYSIS AND MODIFICATION OF LANGMUIR-BLODGETTTHIN-FILMS

The erosion behavior of cadmium arachidate Langmuir-Blodgett films is studied under 270 keV He and Ar ion irradiation. Initial characterizat ion by medium energy time-of-flight backscattering yields a thickness and stoichiometry consistent with an unmodified film. In addition, tim e-of-flight elastic recoil detection is used to monitor the hydrogen e volution from the films as a function of the cumulative dose. After a dose of 5 x 10(14) Ar ions/cm(2), the film is reduced to less than 50% of its initial thickness and depleted in hydrogen. Smaller losses are measured for He at a dose of nearly 1 x 10(15) ions/cm(2). Dramatic c hanges are observed in the interference color of 50-layer films under ion erosion. Measurements by ellipsometry yield thicknesses which are consistent with the backscattering estimates and indicate an increase in the refractive index of the film. The response of cadmium arachidat e to energetic ions is compared with the cadmium salt of omega-tricose noic acid, which can polymerize due to the presence of a C=C double bo nd.