Electron spin resonance in heterostructures with ring molecules of GeSi quantum dots

Heterostructures with annular groups of GeSi quantum dots grown on Si(001) substrates with GeSi nanodisks embedded beneath the surface are investigated by the electron spin resonance technique. It is demonstrated that electrons in annular groups can be localized at the apexes of quantum dots in the annular groups. Narrowing of the electron spin resonance line of the annular electron states localized at the nanodisks is observed. The width of this line decreases when the magnetic field deviates from the structure growth direction, which confirms experimentally the earlier prediction that the spin relaxation time $T_2$ should increase in this case.