Electron and nuclear spin resonance in n-type silicon carbide

Abstract

Some experiments are described of the elctron nuclear double resonance in n-type silicon carbide at low temperatures. With this method the magnetic interaction between the bound donor electron and the 29Si and 13C nuclei is studied. Transitions of the lattice nuclei interacting with the donor electrons cause some change of the level of the electron spin resonance. By means of this effect (ENDOR), the nuclear magnetic resonance of the nuclei surrounding the donor centres was detected. The nuclear resonance frequency is shifted due to the bound donor electron, the shift being dependent on the position of the nucleus with respect to the centre. By means of microwave radiation the nuclear polarization could be enhanced. The nuclear resonance was then observed of the majority of the nuclei of which the resonance frequency is not shifted. By comparing the 29Si and 13C spin-lattice relaxation times with each other it concluded that the donor impurities occupy carbon sites. From the ENDOR spectra the extension of the bound donor electron around the impurity centre is estimated. Assuming a hydrogen-like envelope function a value of 5 Å was found for the orbital radius. This value is consistent with the observed effects of nuclear dynamic polarization and paramagnetic resonance.