Influence Of Thermal Activation Research Articles

Logarithmic detrapping response for holes injected into SiO2 and the influence of thermal activation and electric fields

Relaxation of trapped holes that are introduced into silicon dioxide from silicon by the avalanche injection method is studied under various conditions of thermal activation and external electric fields. It is found that the flat band voltage recovery in time follows a universal behavior in that the response at high temperatures is a time scaled extension of the response at low temperatures. Similar universality exists in the detrapping response at different external bias fields. The recovery characteristics show a logarithmic time dependence in the time regime studied (up to 6000 s). We find that the recovery is thermally activated with the activation energy varying from 0.5 eV for a field of 2 MV/cm to 1.0 eV for a field of −1 MV/cm. There is little discharge in 3000 s at room temperature for negative fields beyond −4 MV/cm. The results suggest that the recovery is due to tunneling of electrons in the silicon conduction band into the oxide either to compensate or to remove the charge of trapped holes.

The domain structure of small grain iron films at elevated temperatures

Observations have been undertaken with Lorentz microscopy on the domain structure, at elevated temperatures, of thin evaporated iron films. The grain size of the films was small, estimated at 20-40 A. At temperatures well below the normal Curie point the magnetic contrast tended to disappear, but returned to its initial configuration when the temperature was lowered again. It is postulated that the films exhibit a quasi Curie point above which they behave as superparamagnetics under the influence of thermal activation. The value of the quasi Curie point is determined by the balance of the particle thermal energy and the restraining intercrystallite forces. A simple calculation indicates that these forces are magnetostatic in origin, and a value is obtained. This value is in reasonable agreement with that obtained using the Lorentz field approximation.