Anestis Katsounaros

Microwave characterization of vertically aligned multiwalled carbon nanotube arrays

Vertically aligned multiwalled carbon nanotube (VACNT) films have been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT films have been extracted. The extracted parameters are verified by full wave simulations and very good agreement has been obtained. The results of the systematic error analysis are presented and the errors are within the acceptable range. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible while maintaining the same absorption level.

Graphene Field-Effect Transistor Model With Improved Carrier Mobility Analysis

This paper presents a SPICE-like graphene field-effect transistor (GFET) model with an improved carrier mobility analysis. The model considers the mobility difference between the electrons and the holes in graphene, as well as the mobility variation against the carrier density. Closed-form analytical solutions have been derived, and the model has been implemented in Verilog-A language. This was compiled into an advanced design system. The proposed model gives excellent agreement between the simulation results and the measurement data for both the hole and electron conduction simultaneously. The model is suitable for the exploration of GFET-based applications, especially for those using the ambipolar transfer property of GFET.

Near-field characterization of chemical vapor deposition graphene in the microwave regime

Near-field measurements were performed at X-band frequencies for graphene on copper microstrip transmission lines. An improvement in radiation of 0.88 dB at 10.2 GHz is exhibited from the monolayer graphene antenna which has dc sheet resistivity of 985 Ω/sq. Emission characteristics were validated via ab initio simulations and compared to empirical findings of geometrically comparable copper patches. This study contributes to the current knowledge of the electronic properties of graphene.

Microwave characterization of a single multi-wall carbon nanotube

A novel estimation of the permittivity and permeability of an individual carbon nanotube is presented using optimization techniques. The complex effective permittivity and effective permeability of a vertically aligned carbon nanotube array are extracted by waveguide measurements. The quasi-Newton optimization technique has been applied to a unit cell of a periodic structure, consisting of solid isotropic cylinders with unknown complex permittivity. As a result, the relative permittivity of an individual carbon nanotube is calculated for each frequency point.

X-band characterization of multi-walled carbon nanotube films

A vertically aligned multi-walled carbon nanotube (VACNT) film has been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT film have been extracted using the Nicolson-Ross-Weir (NWR) approach. The extracted parameters are verified by full wave simulations (CST - Microwave Studio) and very good agreement has been obtained. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible whilst maintaining the same absorption level.