2004 Volume 73 Issue 4 Pages 494-500
Positrons injected into polymer behave asnanometer probes, which can detect the size and amount of intermolecular spaces among polymer structures.Although positrons can probe the characteristics of polymer, they induce a radiation effect on polymer samples.At low temperature, the radiation effect induces free electrons, which can be trapped in a shallow potential created among intermolecular structures after freezing molecular motions.These trapped electrons can be released after the disappearance of the shallow potential due to the reappearance of molecular motion above the relaxation temperature.Thus, positrons can be used as a probe for relaxation studies.Coincidence of Doppler broadening spectroscopy (CDBS) can improve the S/N ratio to 107, which makes it possible to detect trace elements, since CDBS can separate the high-momentum component of core electrons.A pulsed slow positron beam apparatus is necessary for measuring holes in the polymer film and allows the measurement of the characteristics of thin film coated on semiconductors used widely in electronics industries.
