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Focused ion beam implantation of 30-keV Ga+ ions in single-crystalline Si and Ge was investigated by SIMS, using Cs + primary ions for sputtering. Nine different implantation fluences ranging from 1 × 10 13 to 1 × 10 17 Ga + -ions/cm 2 were used, with implanted areas of 40 × 40 µm 2 . The Ga concentration distributions of these implants were determined by SIMS depth profiling. Such 30-keV Ga implantations were also simulated by a dynamic Monte-Carlo code that takes into account the gradual change of the near-surface composition due to the Ga incorporation. In both approaches, an essentially linear increase of the Ga peak concentrations with fluence is found up to ∼1 × 10 16 cm −2 ; for higher fluences, the Ga content approaches a saturation level which is reached at about (1-2) × 10 17 cm −2 . The measured and simulated peak concentrations of the Ga distributions are in good agreement. The most probable ranges obtained from the experiments correspond closely with the respective values from the simulations. The surface morphology caused by Ga + implantation was investigated by atomic force microscopy (AFM). The AFM data indicate that for low fluences (<3 × 10 15 cm −2 ) the surface within the implanted areas is growing outward (i.e. is swelling). For increasingly higher fluences, sputter-induced erosion of the surface becomes dominant and distinct craters are formed for fluences above ∼1 × 10 16 cm −2 . At the boundary of the implanted region a wall-like structure is found to form upon Ga implantation; its height is growing with increasing fluence, reaching a value of ∼15 nm at 1 × 10 17 Ga + -ions/cm 2 . Copyright

Magnetic patterning of antiferromagnetically coupled epitaxial Fe(10nm)∕Cr(0.7nm)∕Fe(10nm)(001) trilayers by irradiation with 30keV Ga+ ions was studied by means of atomic force microscopy, magnetic force microscopy, and Kerr magnetometry. It was found that within a fluence range of (1.25−5)×1016ions∕cm2 a complete transition from antiferromagnetic to ferromagnetic coupling between the two Fe layers can be achieved. The magnetization reversal processes of the nonirradiated, antiferromagnetically coupled areas situated close to the irradiated areas were studied with lateral resolution. Evidence for a lateral coupling mechanism between the magnetic moments of the irradiated and nonirradiated areas was found. Special attention was paid to preserve the flatness of the irradiated samples. Depending on the fluence, topographic steps ranging from +1.5to−2nm between the nonirradiated and irradiated areas were observed. At lower fluences the irradiation causes an increase of the surface height, while for higher fluences the height decreases. It was found that for the particular fluence of 2.7×1016ions∕cm2 no height difference between the irradiated and nonirradiated areas occurs. The results suggest that the irradiation of Fe∕Cr∕Fe trilayers with midenergy ions is an innovative method for magnetic patterning, preserving the initial smoothness of the sample.

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