Modelling the response of polymeric thin-film devices subject to X-ray irradiation

The Monte Carlo technique has been used to model the response of polyphenyl enevinylene-based (PPV) thin-film devices subject to X-ray irradiation. The energy deposition in the PPV film is predominantly due to secondary electr ons generated in surrounding materials for the film thicknesses studied her e (110nm). Similar calculations on silicon devices indicate that secondary radiation effects are not as important in this respect. Hence PPV devices c an be tailored to optimise the response to a degree not possible for Si dev ices. The calculations show that the energy deposited in a PPV film relativ e to that deposited in a Si film of equal thickness can be improved ii om 1 % for a free standing film to similar to 30% for a film surrounded by silic a substrate and encapsulant layers when subject to skeV X-rays.