The influence of interface growth interruption on electron spin relaxation time tau s in GaAs/AlGaAs (1 1 0) quantum wells (QWs) grown by solid source molecular-beam epitaxy (SSMBE) has been investigated by grazing incidence X-ray reflectivity and time-resolved Kerr rotation spectroscopy (TRKR). Various inverted interface interruption times were used in growing QWs. Interface roughness of these QW samples was studied by grazing incidence X-ray reflectivity. The simulated results of reflectivity, curves by standard software indicated that interface roughness decreased as the interface growth interruption time increased. TRKR measurements at room temperature showed that the appropriate growth interruption could increase spin relaxation time in GaAs/AlGaAs QWs drastically. This dramatic increase was explained by the suppression of the D'yakonov-Perel' interaction. (c) 2006 Elsevier B.V. All rights reserved.