The structure development of buried oxide in low-dose separation of implanted oxygen wafers implanted at acceleration energies of 160, 130, and 100 keV was investigated by cross-section and high resolution transmission electron microscopy. The threading dislocation density in the superficial silicon layer was determined by Secco etching. The results indicate that the thickness of superficial silicon, the buried oxide (BOX) integrity, effective BOX thickness, Si/SiO2 interface, and threading dislocation density have a strong energy dependence. For the samples implanted at a dose of 5.5X 10(17) cm(-2), the optimum energy is 160 keV, while at a dose of 4.5x 10(17) cm(-2), it is 130 keV. The mechanism was discussed.