The microwaves electromagnetic properties, i.e. the complex permittivity, of single cells determine how this radiation is transmitted, reflected or absorbed by biological tissues. This information is important for the development microwave medical applications in diagnostics and therapy. Moreover, it is also crucial to assess the potential dangerous effects of the exposure to microwave radiations. Dielectric spectroscopy performed allowed to quantify the complex permittivity of tissues and whole single cells. However, there is a lack of information at the sub-cellular and intracellular level, due to the inherent limitations of the techniques, to resolve the dielectric response at the nanoscale. In recent years, Near-Field Scanning Microwave Microscopy (NF-S03) has appeared as promising alternative to obtain images related to the dielectric response of samples, with high spatial resolution. In S03, the local reflection of microwaves from the sample is measured by means of a sharp probe scanned in close proximity to the sample, i.e. within the near-field region. The reflection can be related to the electrical impedance of the samples, and from this, the local complex permittivity can be retrieved. The near-field region ensures the good lateral resolution of the technique, far below the wavelength of the radiation used. S03 has been only scarcely applied to biological samples, and the few studies are limited to qualitative findings. This is due, among other reasons, to the complexity of the interpretation of the data, especially in case of tall irregular samples like cells, where the topography crosstalk effect dominates the signal acquired, thus masking the dielectric response. The objective of my Thesis was precisely to use this technique to quantify the local nanoscale dielectric response of a single cell at microwave frequency. My research focused primarily in the elaboration and implementation of the analysis methodologies suitable to obtain quantitative information from S03 measurements. I elaborated a methodology to disentangle and remove the topography crosstalk effect in the capacitance images acquired by S03, which allows to extract new capacitance images only related to the intrinsic dielectric response of the sample, and therefore suitable for the quantification. I extracted the permittivity of the sample from the intrinsic capacitance images, by means of data analysis procedures which I adapted from the one available for low frequency measurements within the research group. Among these, the procedures to determine tip and sample geometries and to obtain the permittivity. The procedures were validated on reference samples. I first analysed heterogeneous inorganic thin film, exhibiting large height variations comparable to the ones of bacterial cells. I obtained intrinsic capacitance images at around 19 GHz in contact mode and show these can be directly related to the permittivity of the samples, without the need of theoretical models or the knowledge of the system geometry, and therefore represent maps of the microwave permittivity. I also show that in case of images acquired in intermittent contact mode the interpretation of the capacitance images in terms of the electric permittivity is much more complex. Finally, I obtained intrinsic images, at ̃19 GHz, of a single E.coli bacterium, in dry and humid conditions, and, with the help of theoretical models, I extracted the local permittivity. These findings represent the first quantification of the of a single cell ever done at microwaves at the nanoscale, and thus show that S03 is sensitive to the cell constituent and the environment humidity. The results obtained prove that, despite the complexity of the data analysis, the microwave permittivity of biological samples can be quantified with nanoscale resolution, from S03 capacitance images.

Microwave Materials Characterization is an edited book discussing recent researches on basic and innovative measurement techniques for the characterization of materials at microwave frequencies, in terms of quantitative determination of their electromagnetic parameters, namely the complex permittivity and permeability. It is divided into two parts: Part 1, including original contributions on advanced techniques for the characterization of dielectric materials, and Part 2, devoted to the microwave characterization of biological tissues.

This volume will be devoted to the technical aspects of electrical and electromechanical SPM probes and SPM imaging on the limits of resolution, thus providing technical introduction into the field. This volume will also address the fundamental physical phenomena underpinning the imaging mechanism of SPMs.

Ability to measure local dielectric constant and conductivity at nanoscale is desir- able for many research disciplines. Traditional transport measurements and many scanning probe techniques require ohmic contacts to the sample, which further com- plicates the sample preparation and is a low throughput process. Techniques based on high-frequency coupling is advantageous over these techniques since the measure- ments rely on the capacitive coupling between the tip and the sample. Among the high-frequency probes, near-field microwave microscopy sits on the sweet spot with the advantages from the high frequency coupling, but still maintains high contrast between metal and insulator. Implementing microwave microscopy technique is no trivial task. The first part of this thesis describes various engineering aspects during the developmental stage of our microwave microscopy, which we call microwave impedance microscope (MIM). We will begin with introduction to the principle of near-field microscopy, and follow by describing various components of MIIM. The second part of the thesis devotes to the study of nanoscale electronic inhomogeneity both at room temperature and low temperature. The room temperature works provide examples of application of MIM for nanoscale electrical characterization in nano graphene and semiconductor devices. The low temperature studies focus on the phase transition in pervoskite manganites and edge states of two-dimensional electron gas. In pervoskite manganites, we provide direct observation of the phase-separation and the glassy behavior of manganites. In the two-dimensional systems, we study the formation edge states during quantum Hall and quantum spin Hall effects. Finally, we concludes the thesis with plans for future developments and scientific problems.

There are two words that describe the direction of today's electronic technology, smaller and faster. With the ever decreeing size scientists and engineers must have a way to characterize materials in the nm range. In this thesis characterization of nano-materials is discussed based on scanning probe microscopy and an in-depth look at RF/microwave frequencies by scanning microwave microscopy. Recently, low-temperature spin-sprayed ferrite films (Fe3O4) with a high self-biased magnetic anisotropy field have been reported, showing FMR frequency>5 GHz. Such films hold great potential for RF/microwave devices and find immediate applications. In this study, we performed in situ scanning microwave microscopy (SMM) characterization at frequencies between 2.0 GHz and 8.0 GHz. The grain boundary appeared to be more conductive, which might be caused by charge accumulation in the grain boundary space-charge region.

Connect basic theory with real-world applications with this practical, cross-disciplinary guide to radio frequency measurement of nanoscale devices and materials. • Learn the techniques needed for characterizing the performance of devices and their constituent building blocks, including semiconducting nanowires, graphene, and other two dimensional materials such as transition metal dichalcogenides • Gain practical insights into instrumentation, including on-wafer measurement platforms and scanning microwave microscopy • Discover how measurement techniques can be applied to solve real-world problems, in areas such as passive and active nanoelectronic devices, semiconductor dopant profiling, subsurface nanoscale tomography, nanoscale magnetic device engineering, and broadband, spatially localized measurements of biological materials Featuring numerous practical examples, and written in a concise yet rigorous style, this is the ideal resource for researchers, practicing engineers, and graduate students new to the field of radio frequency nanoelectronics.