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The reflection properties of 300 nm periodically structured silicon surfaces with depth varying between 35 and 190 nm, prepared by interference lithography, were examined in the range 200 nm<λ<3000 nm. A decrease in the reflectivity that becomes stronger with increasing structure depth is observed below 1000 nm. This broad-band reduction is caused by diffraction effects at short wavelengths and by the `moth-eye effect' at long wavelengths. The results show a universal behaviour in the optical-path to wavelength ratio dependence of the reflectivity and are in good agreement with the results obtained for the `moth-eye effect' from the effective medium theory.

We present experimental results on the characterization of commercially available magnetic force microscopy (MFM) thin film tips as a function of an external magnetic field. Well defined magnetic stray fields are produced using current carrying rings with radii ranging between 603 and 2369 nm fabricated by electron-beam lithography directly imaged by MFM. Treating the MFM tip as a point probe, the analysis of the image contrast as a function of both the magnetic stray field and the lift height allows for a quantitative determination of effective magnetic dipole and monopole moments of the tip as well as their imaginary location within the real physical tip. Our systematic study gives a quantitative relationship on how absolute values of the magnetic dipole and monopole moments and their location within the tip depend on a characteristic decay length of the z component of the magnetic field being detected. From this we can estimate the effective tip volume of the real physical thin film tip relevant in MFM imaging.

Experimental results on the characterization of commercially available magnetic force microscopy (MFM) thin film tips as a function of an external magnetic field are presented. Magnetic stray fields with a definitive z-component (perpendicular to the substrate) and a magnetic field strength of up to Hz=±45 Oe are produced with current carrying parallel nanowires with a thickness of t=60 nm, which are fabricated by electron-beam lithography. The magnetic fields are generated by electrical dc-currents of up to ±6 mA which are directed antiparallel through the nanowires. The geometry and the dimensions of the nanowires are systematically varied by choosing different wire widths w as well as separations b between the parallel wires for two different sets of samples. On the one hand, the wire width w is varied within 380 nm&lt;w&lt;2460 nm while the separation b≈450 nm between the wires is kept constant. On the other hand the separation b between the parallel wires is varied within 120 nm&lt;b&lt;5100 nm, while the wire width w=960 nm is kept constant. For all the geometrical configurations of parallel wires the resulting magnetic contrast is imaged by MFM at various tip lift-heights. By treating the MFM tip as a point probe, the analysis of the image contrast as a function of both the magnetic field strength and the tip lift height allows one to quantitatively determine the effective magnetic dipole and monopole moments of the tip as well as their imaginary locations within the real physical tip. Our systematic study quantitatively relates the above point-probe parameters to (i) the dimensions of the parallel wires and (ii) to the characteristic decay length of the z-component of the magnetic field of parallel wires. From this the effective tip-volume of the real thin film tip is determined which is relevant in MFM-imaging. Our results confirm the reliability of earlier tip calibration schemes for which nanofabricated current carrying rings were used instead of parallel wires, thereby proving that the tip calibration equations depend on the underlying stray field geometry. Finally, we propose an experimental approach which allows one to measure the magnetization of nanoscale ferromagnetic elements with an in-plane orientation of the magnetization, quantitatively, by using a calibrated MFM-tip.

We have investigated the low temperature resistance behavior and the magnetoresistance of single-domain cobalt nanowires of various thicknesses ranging between 5 nm and 32 nm and wire widths ranging down to 32 nm. The nanowires are coated with insulating carbon on three sides to prevent oxidation. Magnetic force microscopy investigations show that nanowires with widths below 800 nm are in a single-domain-like remanence state. The magnetoresistance is negative and is well explained by the anisotropic magnetoresistance ͑AMR͒. At low temperatures T Ͻ 30 K a logarithmic resistance increase is observed with decreasing temperature, which is consistently explained as originating from enhanced electron-electron interactions in two dimensions. Quantum corrections due to weak electron localization are not observed which is in contrast to recent theoretical predictions for two-dimensional ferromagnetic systems. However, the results are consistent with our earlier results obtained for platinum-capped and unprotected cobalt nanowires. A reduction of the wire width below about 400 nm yields a crossover behavior from two-dimensional to one-dimensional behavior with respect to the quantum corrections of the resistance.