  We report on measurements of the spin relaxation time T1 of individual
electron spins in the few electron regime of a Si/SiO2-based quantum dot (QD).
Energy-spectroscopy of the QD has been performed using a charge sensing
technique. The spin relaxation times are subsequently measured in the
time-domain by a pump-and-probe method. For the QD that contains an unpaired
spin, likely only a single electron, we find that T1 depends strongly on the
applied magnetic field. Possible mechanisms leading to the observed spin
relaxation are discussed.
