Microstructure Of Fe-implanted Sapphire And Co-implanted Silicon (As-implanted Samples And Annealing Samples)

Ion implantation is an effective technique to modify the physical, chemical and mechanical properties of material surface layer. Ion-implanted sapphire has excellent mechanical properties, which often serves as structural ceramic. In recent years, Fe-implanted sapphire has been found to have excellent magnetic properties, which may serve as data-storage medium in the future. Ion implantation has also been used to form buried CoSi₂ layers, which may serve as a new generation interconnect leading wire in integrated circuit in the future. But the microstructure of ion-implanted sapphire and silicon has been understood not clearly enough at present. Since microstructures of materials decide properties of materials, it is necessary to investigate the microstructure of ion-implanted samples deeply.Microstructure of Fe-implanted sapphire and Co-implanted silicon (as-implanted samples and annealing samples) is investigated by transmission electron microscopy. The primary conclusions are listed as follows:Noα-Fe particles precipitate in sapphire implanted with 1×10¹⁶ Fe ions/cm² and there is high-density defect in implanted zone, but the implanted layer has the crystalline nature. In sapphire implanted with 1×10¹⁷ Fe ions/cm² there are many small particles about 1-3 nm, which should beα-Fe considering the Mossbauer results, and the defect-rich implanted layer still has the crystalline nature.In sapphire implanted with iron and annealed in a reducing atmosphere the implanted Fe ions precipitate as theα-Fe particles. Most of theα-Fe particles have the orientation relationship (OR) of (111)_α-Fe//(0001)_sapphire and [1(?)0]_α-Fe//[11 (?) 0]_sapphire with sapphire, which was also discovered by Ohkubo et al. Only a small quantity of theα-Fe particles have the deviation from this OR and the maximum deviation is less than 3°. The largeα-Fe particles clearly have faceted outlines. Two typical outlines have been observed. One outline consists of {0001}, {11(?) 0} and {2(?)3} of sapphire. The other outline consists of {0001}, {11(?) 0}, {2(?)3} and {2(?)} of sapphire. The coincidence of reciprocal lattice points method has been utilized to confirm that the OR above is preferred in theα-Fe/sapphire system and another OR of (110)_α-Fe//(0001)_sapphire and <111>_α-Fe//<5(?)0>_sapphire reported before is the secondary preferred orientation.In sapphire implanted with iron and annealed in an oxidizing atmosphere the implanted Fe ions precipitate asα-Fe₂O₃ islands and spinel islands on the specimen surface. Theα-Fe₂O₃ islands have the orientation relationship of [0001]_{α-Fe2O3}//[0001]_sapphire and (11(?)0)_{α-Fe2O3}// (11(?) 0)_sapphire with sapphire. The typical outline ofα-Fe₂O₃ islands consists of two (0001) and six {10(?)2} planes ofα-Fe₂O₃. The interfaces betweenα-Fe₂O₃ islands and sapphire are, semicoherent. When imaged along the [(?)100]_sapPhire direction, the projected Burgers vector is determined to be 1/6[11 (?) 0]_sapphire. When imaged along the [11 (?) 0]_sapPhire direction, the projected Burgers vector is determined to be 1/2[(?)100]sapphire.Two ORs between the spinel islands and sapphire substrate have been discovered. One is (111)_spinei // (0001)_sapphire and [11(?) ]_spinei // [11(?) 0]_sapphire, which is consistent with the most common OR between spinel and sapphire. The other is (11(?) )_spinel // (0001)_sapphire and [111]_spinel//[11(?) 0]_sapphire, which is discovered for the first time. The interfaces between the spinel islands and sapphire substrate are an incoherent interface.In silicon implanted with Co there are many small CoSi₂ precipitates and the CoSi₂ precipitates have the orientation relationship of [110]_CoSi2//[110]_Si and (2(?) 0)_CoSi2//(2(?) 0)_Si with silicon substrate. The outline of hexagonal CoSi₂ precipitates consists of {001} and {1(?)1} planes of silicon. At the same time there are many rod-like {113} defects and some Si interstitials clusters corresponding to the initial configuration of {113} defects at the end-of-range damage zone. With annealing in vacuum the small CoSi₂ precipitates don't form the continuous buried CoSi₂ layers, but form large CoSi₂ precipitates.