Stripline ͑SL͒, vector network analyzer ͑VNA͒, and pulsed inductive microwave magnetometer ͑PIMM͒ techniques were used to measure the ferromagnetic resonance ͑FMR͒ linewidth for a series of Permalloy films with thicknesses of 50 and 100 nm. The SL-FMR measurements were made for fixed frequencies from 1.5 to 5.5 GHz. The VNA-FMR and PIMM measurements were made for fixed in-plane fields from 1.6 to 8 kA/ m ͑20-100 Oe͒. The results provide a confirmation, lacking until now, that the linewidths measured by these three methods are consistent and compatible. In the field format, the linewidths are a linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter ␣ value of 0.007 and zero frequency intercepts in the 160-320 A / m ͑2-4 Oe͒ range. In the frequency format, the corresponding linewidth versus frequency response shows a weak upward curvature at the lowest measurement frequencies and a leveling off at high frequencies.

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A scanning microwave microscope (SMM) for spatially resolved capacitance measurements in the attofarad-to-femtofarad regime is presented. The system is based on the combination of an atomic force microscope (AFM) and a performance network analyzer (PNA). For the determination of absolute capacitance values from PNA reflection amplitudes, a calibration sample of conductive gold pads of various sizes on a SiO(2) staircase structure was used. The thickness of the dielectric SiO(2) staircase ranged from 10 to 200 nm. The quantitative capacitance values determined from the PNA reflection amplitude were compared to control measurements using an external capacitance bridge. Depending on the area of the gold top electrode and the SiO(2) step height, the corresponding capacitance values, as measured with the SMM, ranged from 0.1 to 22 fF at a noise level of ~2 aF and a relative accuracy of 20%. The sample capacitance could be modeled to a good degree as idealized parallel plates with the SiO(2) dielectric sandwiched in between. The cantilever/sample stray capacitance was measured by lifting the tip away from the surface. By bringing the AFM tip into direct contact with the SiO(2) staircase structure, the electrical footprint of the tip was determined, resulting in an effective tip radius of ~60 nm and a tip-sample capacitance of ~20 aF at the smallest dielectric thickness.

We show that the magnetization dynamics of soft ferromagnetic thin films can be tuned using rare-earth (RE) dopants. Low concentrations (2 to 10%) of Tb in 50 nm Ni 81 Fe 19 films are found to increase the Gilbert magnetic damping parameter over two orders of magnitude without great effect on easy axis coercivity or saturation magnetization. Comparison with Gd dopants indicates that the orbital character of the Tb moment is important for transferring magnetic energy to the lattice. Structural transformations from the crystalline to the amorphous state, observed over the first 2%-10% of RE doping, may play a contributing but not sufficient role in damping in these films. The approach demonstrated here shows promise for adjusting the dynamical response, from underdamped to critically damped, in thin film materials for magnetic devices Index Terms-Magnetization dynamics, Ni-Fe alloys, rare-earth.

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Nonuniform fields decrease the accuracy of dielectric characterization by microwave cavity perturbation. These fields are due to the slot in the cavity through which the sample is inserted and the boundary between the sample and the metallic walls inside of the cavity. To address this problem, we measured the natural frequency and damping ratio of a resonant cavity as a sample is inserted into the rectangular cavity. We found that for a range of cavity filling fractions, a linear regression on the natural frequency and damping ratio versus the effective volume fraction of the sample in the cavity could be used to extract the complex permittivity of the sample. We verified our technique by measuring a known quartz substrate and comparing the results to finite-element simulations. When compared to the conventional technique, we found a significant improvement in the accuracy for our samples and measurement setup. We confirmed our technique on two lossy samples: a neat stoichiometric mixture bisphenol A epoxy resin and one containing a mass fraction of 3.5% multi-walled carbon nanotubes (MWCNTs). At the mode (7.31 GHz), the permittivity and loss tangent of the epoxy were measured to be and , respectively. The epoxy with a mass fraction of 3.5% MWCNTs had a permittivity of and loss tangent of .Index Terms-Bisphenol A epoxy, metrology, microwave, multi-walled carbon nanotubes (MWCNTs), nanocomposites, noncontact, nondestructive, resonator.

The scanning microwave microscope is used for calibrated capacitance spectroscopy and spatially resolved dopant profiling measurements. It consists of an atomic force microscope combined with a vector network analyzer operating between 1–20 GHz. On silicon semiconductor calibration samples with doping concentrations ranging from 1015 to 1020 atoms/cm3, calibrated capacitance-voltage curves as well as derivative dC/dV curves were acquired. The change of the capacitance and the dC/dV signal is directly related to the dopant concentration allowing for quantitative dopant profiling. The method was tested on various samples with known dopant concentration and the resolution of dopant profiling determined to 20% while the absolute accuracy is within an order of magnitude. Using a modeling approach the dopant profiling calibration curves were analyzed with respect to varying tip diameter and oxide thickness allowing for improvements of the calibration accuracy. Bipolar samples were investigated and nano-scale defect structures and p-n junction interfaces imaged showing potential applications for the study of semiconductor device performance and failure analysis.