In this paper, a silicon lost molding process is described for fabricating high aspect ratio microcoils with high Q factors. Deep reactive ion etching, electroplating and XeF2 silicon etching are utilized in this process. Microcoils with an aspect ratio of 16 and inner diameters from 80 µm to 200 µm are fabricated. The electrical characteristics are measured using a network analyzer and a two-terminal radio frequency probe. For a microcoil with an inner diameter of 130 µm, three windings and an outer diameter of 240 µm, the quality factor is 85 at a frequency of 1.6 GHz. The proximity effect and parasitic capacitance are found to be the key issues for limiting the maximum Q factor of the microcoil at high frequencies. The high Q values of the microcoils make them attractive for high resolution micro-MRI (magnetic resonance imaging) applications.

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One of the most important advantages of graphene is the capability of dynamically tuning its conductivity by means of chemical doping or gate voltage. Based on this property, we propose a planar gradient index graphene-based lens transforming spherical waves of the transverse-magnetic (TM) surface plasmon polariton (SPP) wave to plane waves of the TM SPP wave with specific beam deflections. Using numerical simulations, it is confirmed that a single-atomic-layered graphene can be a platform for planar gradient-index lens, which can be applied to modulate the propagation of SPP waves.

Thermal scanning probe lithography is a direct-write patterning method that uses a heated scanning probe tip to remove thermal resist. The most widely used thermal resist is polyphthalaldehyde. Another alternative thermal resist, Parylene C is introduced in this letter. It has been found that Parylene C has a wide process latitude as a thermal resist under our experimental conditions. A high resolution of ∼40 nm can be achieved in our optimised process. In addition, patterns in parylene layer can be transferred directly into the substrate with deep reactive ion etching without an additional hard mask, thus simplifying the fabrication process.

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