Low-Atomic-Number Nanometric Film Production Method for keV Electron Scattering Measurements

Attenuating mediums, targets and barriers made of submicronic layers with low average atomic number (low Z) and minimal electronic density that reduces the elastic scattering and absorption of radiation are required for many applications. This work describes the development and characterization of submicronic Lexan (Polycarbonate) polymer foils with low Z for two new electron inelastic mean free path assessment methods. Lexan layers with thicknesses of 120 nm to 240 nm were developed and fabricated using spin coating. The submicronic layers were characterized by AFM and CSI for thickness, roughness and levelness. Roughness was found to be 1.0-2.4 nm rms, and the change in total thickness was within ± 7.5%. The results of total current measurements using 177 nm Lexan foil irradiated under an SEM electron beam were compared to those for a similar polymer foil. The first step of a wide spectrum method experiment was performed at the ESRF using Lexan submicronic layers on a silicon substrate. The signal peak and the multiple inelastic scattering peak of the Lexan spectrum was similar to those previously measured on carbon films. This study supported the suitability of the developed Lexan films for electron scattering measurement