Transport in Si and Ge polymers above and below T g-comparison with a-Se and other glasses

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Drift mobility measurement on prototypical sigma bonded Si and Ge backbone polymers carried out over a temperature range broad enough in each case to encompass the glass transition are described. Below T g the hole drift mobility exhibits a convoluted field and temperature dependence similar in detail to that observed in diverse glassy media, including chalcogenides and molecularly doped polymers. It is demonstrated that drift mobility in Si and Ge polymers can be directly modified by doping. A relatively abrupt and reversible change in transport activation occurs when various Si and Ge polymers are thermally cycled through their respective glass transitions. A similar effect on mobility has been observed in other organic and inorganic molecular glasses, including a-Se. However, it is only in Se and Se based glasses where transport is controlled by thermodynamic defects, that pronounced mobility hyteresis associated with glassification and relaxation, is simultaneously observed.