No abstract

Ge implanted with 1 MeV Si + at a dose of 1 ϫ 10 15 cm −2 creates a buried amorphous layer that, upon regrowth, exhibits several forms of defects-end-of-range ͑EOR͒, regrowth-related, and clamshell defects. Unlike Si, no planar ͕311͖ defects are observed. The minimal EOR defects are small dotlike defects and are very unstable, dissolving between 450 and 550°C. This is in contrast to Si, where the EOR defects are very stable. The amorphous layer results in both regrowth-related defects and clamshell defects, which were more stable than the EOR damage.

Few transmission electron microscopy ͑TEM͒ studies of single crystal diamond have been reported, most likely due to the time and difficulty involved in sample preparation. A method is described for creating a TEM cross section of single crystal diamond using a focused ion beam and in situ lift-out. The method results in samples approximately 10 m long by 3 m deep with an average thickness of 100-300 nm. The total time to prepare a cross-sectional TEM sample of diamond is less than 5 h. The method also allows for additional thinning to facilitate high resolution TEM imaging, and can be applied to oddly shaped diamond samples. This sample preparation technique has been applied to the study of ion implantation damage in single crystal diamond and its evolution upon annealing. High-pressure-high-temperature diamonds were implanted with Si + at an energy of 1 MeV and a temperature of 30°C. One sample, with a ͑110͒ surface, was implanted with a dose of 1 ϫ 10 14 Si cm −2 and annealed at 950°C for 10 and 40 min. No significant defect formation or evolution was discernible by cross-sectional transmission electron microscopy. Another sample, with a ͑100͒ orientation, was implanted with 1 MeV at 1 ϫ 10 15 Si cm −2 and annealed at 1050°C for 10 min. Prior to annealing, a heavily damaged but still crystalline region was observed. Upon annealing, the sample showed no signs of conversion either to an amorphous form of carbon or to graphite. This is unexpected as the energy and dose are above the previously reported graphitization threshold for diamond. Higher annealing temperatures and possibly a high vacuum will be required for future study of defect formation, evolution, and phase transformations in ion-implanted single crystal diamond.

Cross-sectional transmission electron microscopy was used to study defect formation and evolution in the ͑001͒ Ge and Si wafers implanted with 1 MeV Si + and 40 keV Si + at a dose of 1 ϫ 10 14 cm −2 . As expected, upon annealing, the ͕311͖ extended defects form and subsequently dissolve at the projected range for nonamorphizing implants into Si. However, in Ge, no ͕311͖ defect formation is observed for this nonamorphizing implant after annealing at temperatures between 350 and 850°C. Instead, for the MeV implant, small dotlike defects are observed in Ge, which dissolve upon annealing between 650 and 750°C for 10 min.