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A new near-field optical microscope working in transmission is presented. Lateral optical resolution less than 10 nm is obtained with a pure metallic probe. Polarization images of a metallic step confirmed the good resolution by comparison with an analytical model. We also demonstrate the capability of the microscope to obtain images with polarization effects. The good resolution is used for the observation of small gold aggregates which confirm that this microscope is able to make spectroscopic measurements of the optical effect induced by a nanometric scale particle. The polarization sensibility allows us to measure near-field magneto-optical contrast on a multi-layer sample with magnetic domains. These results are promising for magneto-optical characterization with nanometre resolution.

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Both geometrical and electrical asymmetry effects in capacitive argon discharges are investigated using a two-dimensional particle-in-cell coupled with Monte Carlo collision model. When changing the ratio of the top and bottom electrode surface areas and the phase shift between the two applied harmonics, the induced self-bias was found to develop separately. By adjusting the ratio between the high and low harmonic amplitudes, the electrical asymmetry effect at a fixed phase shift can be substantially optimized. However, the self-bias caused by the geometrical asymmetry hardly changed. Moreover, the separate control of these two asymmetry effects can also be demonstrated from their power absorption profiles. Both the axial and radial plasma density distributions can be modulated by the electrical asymmetry effect.