Page 35 Figure (a) Envelopes of the measured Kerr rotation at B=2T in the sample of Fig taken with 1011 electrons cm−2/pulse The resonant excitation energy decreases from 2.70eV to 2.61eV as the temperature varies from 5.7K to 270K Amplitude changes have been normalized at zero delay, (b) 5Room temperature Kerr rotation at 2T at Eex=2.60eV and 1011 electrons cm−2/pulse (c) Room temperature Kerr rotation at IT with 5×1011electrons cm−2/pulse The excitation is at Eex=2.72eV, 20 meV above the ZnSe bandgap energy Tai ngay!!! Ban co the xoa dong chu nay!!! 1.3.2 Thin films and bulk semiconductors: II–VI and III– V systems Systematic studies on doped ZnSe epilayers show spin lifetimes of 1.6ns at 275K and equilibrium electron concentrations as low as 5×1016cm−3, suggesting that the room temperature spin precession which we observe is a general feature of n-doped semiconductors In fact, these bulk samples exhibit an even weaker temperature dependence than seen in the QW structures, with the spin lifetime decreasing only