Lacey, S D (1971) Electron paramagnetic resonance in silicon. Doctoral thesis, Keele University.

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Electron Paramagnetic Resonance (E.P.R.) in silicon doped with the shallow Group V donors phosphorus and arsenic has been studied over the temperature range from 20 to 5O°K. The range of donor concentrations examined was sufficient for exchange to be possible in the more highly doped samples, all samples exhibiting a resonance characteristic of bound donor electrons at 20°K.
The observed reduction in the hyperfine splitting with increasing temperature is interpreted as being due to the phonon-induced transitions of electrons between the various 1s hydrogen-like states. For phosphorus donors an estimate of 10.7 +- 0.4 meV is obtained tor the valley-orbit splitting. The greater value of this splitting for arsenic donor results in an insignificant reduction in the hyperfine splitting for arsenic over the same temperature range.
Simultaneous with the reduction in the hyperfine splitting the linewidth and shape change. Although the above mechanism gives a calculated width of the correct order of magnitude, the increasing linewidth with temperature is better described by an activation energy of half the donor ionization energy. The exchange scattering of the bound donor electrons by conduction electrons is therefore thought to be the dominant
source of the linewidth, such that with the increasing exchange frequency with temperature the hyperfine lines will eventually be averaged out and replaced by a single line. For phosphorus and arsenic donor concentrations at approximately 5.10x17 cm-3 this narrowing single line was only observed for phosphoros. The difference in the donor ionisation energies is thought sufficient to prevent its observation in the case of arsenic.
A possible alternative explanation of the above effects, due to the phonon-induced hopping of electrons from electronically occupied to neighbouring unoccupied sites, was also examined. Calculation demon-states that the experimental results cannot be interpreted in this

Item Type: Thesis (Doctoral)
Subjects: Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Depositing User: Lisa Bailey
Date Deposited: 19 Feb 2019 11:56
Last Modified: 19 Feb 2019 11:56

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