Electron-paramagnetic-resonance study of metallic Si: P with iron

We have observed the electron paramagnetic resonance of iron ({≈} 1 ppm) in metallic Si: P in the temperature range 1.4-77 K for electron concentrations ND=(3-100)×10¹⁸ cm^-3. The single observed line is a strongly coupled (bottlenecked) local-moment conduction-electron resonance, with the local-moment g value (gd=2.000) different from the value (2.070) observed for Fe⁰ in semiconducting silicon. For electron concentrations below 2 ×{} 10¹⁹ cm^-3, gd and the intrinsic local-moment relaxation rate (1γTdl≈6 G) do not depend on ND. The spin-flip scattering cross section for conduction electrons on iron is not found to depend on ND but to increase with temperature with σsf=2×10^-17 cm² at 77 K. Above 2 ×{} 10¹⁹ cm^-3 the low-temperature broadening and g shift decrease as ND increases until at 10²⁰ cm^-3 no effect on the conduction-electron spin resonance is seen upon adding iron to the sample.