Effects of helium ion double implantation on CD bubble device

Abstract

Effects of helium ion double implantation on contiguous disk (CD) bubble devices have been examined by x-ray diffraction, FMR, and annealing techniques. The results were compared with static and dynamic performance of CD devices. Samples had a composition of Sm0.29Lu0.40Y1.42Ca0.89Fe 4.11Ge0.89O12 with stripe width 3 μm, Hc=143 Oe and were implanted with 190-keV helium at 4.5×1015 He+/cm2 and 100-keV helium at 3 ×1015 He+/cm2. X-ray diffraction curves show that He ion double implantation gives a more uniform strain profile with a main strain of 0.84% and a strain induced anisotropy field of 3100 Oe. FMR spectrum results show an implantation induced anisotropy field of 3185 Oe which is in good agreement with x-ray diffraction result. The main strain decreases linearly with the annealing temperature Ta extrapolating to zero at l000 °C. The implantation induced anisotropy field also decreases with Ta, but exhibits an excess of 600 Oe over the strain anisotropy field. This excess is attributed to the suppression of growth induced anisotropy by He ion implantation. The measurements of the bubble collapse field and propagation margin on a CD track with 12-μm period at 100 kHz show that annealing at temperatures higher than 300 °C causes the performance of CD devices to degrade very rapidly. The margin becomes narrow and the minimum drive field increases. Annealing above 500 °C will kill the device.