Cross-sectional transmission electron microscopy method and studies of implant damage in single crystal diamond

Abstract

Few transmission electron microscopy (TEM) 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 10μm long by 3μm deep with an average thickness of 100–300nm. The total time to prepare a cross-sectional TEM sample of diamond is less than 5h. 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 1MeV and a temperature of 30°C. One sample, with a (110) surface, was implanted with a dose of 1×1014Sicm−2 and annealed at 950°C for 10 and 40min. No significant defect formation or evolution was discernible by cross-sectional transmission electron microscopy. Another sample, with a (100) orientation, was implanted with 1MeV at 1×1015Sicm−2 and annealed at 1050°C for 10min. 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.