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Abstract
A natural semiconducting diamond was pre-heated at 1397°C, irradiated at 77 K with 1.80 × 1016 electrons/cm2 at an energy of 1 MeV and heated at several temperatures in the range 201° to 1394°C. Measurements were made of the electrical resistivity, the Hall coefficient and the infrared absorption at 0.348 eV.
The theoretical, treatment-induced Hall mobility is calculated at room temperature on the assumption that the treatment-induced scattering arises exclusively from singly charged centres. This calculated mobility (μI) is normally appreciably greater than the value determined experimentally (μs). If μI is equated to μs, the minimum number of electronic charges per induced donor centre is found to lie in the range 7.7 to 52. These values are improbably large. Hence the induced scattering probably does not arise exclusively from ionized centres.
The total mobility is that resulting from the combination of all scattering. The theoretical temperature dependence of the total mobility is calculated for the general case. The shift in the temperature at which the maximum of this mobility occurs as the concentration of ionized centres is changed, is in qualitative agreement with that which is commonly observed experimentally.
The experimental temperature dependence of the reciprocal total mobility at several stages of heating indicates that the degree of lattice scattering changes, thereby explaining the failure to account for the induced scattering solely in terms of changes in the concentration of ionized centres. It is postulated that the changes in lattice scattering result from variations in the size and concentration of clusters of interstitial carbon atoms. This interpretation is found to be consistent with certain observations reported in the literature.