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Near-field scanning microwave microscopy (SMM) employs microwave radiation to image and characterize samples down to the atomic scale, including soft biological structures or inorganic materials, such as ferroelectric films. However, SMM generally also senses sample topography; hypersensitivity to topography becomes problematic with additional parasitic contributions and may partially or completely mask nontopographic sample features in the data, such as contrast in electrical conductivity or permittivity. This work proposes a simple and effective procedure to remove unwanted parasitic effects from SMM images. Differently from existing procedures, the method is applicable either in postprocessing or in real time, i.e., during the scanning operation. This allows the immediate visualization of nontopographic sample features in the instrument screen. As a proof of concept, hafnium zirconium oxide (HfZrO) ferroelectric film with high surface roughness is studied; unwanted contributions were removed from SMM data, providing a clear map of the sample ferroelectric structure that was originally hidden. [ABSTRACT FROM AUTHOR]

The inverted scanning microwave microscope (iSMM) is a recently developed variety of scanning microprobe microscopes. Similar to a scanning microwave microscope (SMM), the iSMM is sensitive to not only surface structure, but also electromagnetic properties below the surface. Different from the SMM, the iSMM can be converted from any scanning probe microscope, such as an atomic force microscope (AFM) and a scanning tunneling microscope, with a simple metal probe to outperform the SMM in terms of ruggedness, bandwidth, sensitivity, and dynamic range. This letter reports the first iSMM images of a vital mitochondrion in an isotonic glucose solution. Compared to the AFM and SMM, the iSMM offers more insights into the mitochondrion. This shows the potential of iSMM for noninvasive and label-free imaging and characterization of subcellular structures. [ABSTRACT FROM AUTHOR]

Often, a student comes in excited by a revolutionary idea. When this happens, we invite the student to check the literature carefully and, moreover, to extend the search way back, for more than a century, in fact. For example, encouraged by Albert Einstein, Edward H. Synge introduced the concept of a near-field scanning microscope in the 1928 paper "A Suggested Method for Extending Microscopic Resolution Into the Ultramicroscopic Region" [1]. He claimed to have overcome the "...axiom in microscopy, that the only way to extend resolving power lies in the employment of light of smaller wavelength." For subwavelength resolution of a biological sample, Synge proposed to place an opaque screen with a 10-nm diameter pinhole within 10 nm of the sample (Figure 1). Light passing through the pinhole and the sample is focused on a photodetector. By moving the screen laterally in 10-nm steps, the sample is imaged with 10-nm resolution, regardless of the wavelength of the light. Later, what he proposed became known as a scanning near-field optical microscope (SNOM). [ABSTRACT FROM AUTHOR]

This article reports the first quantitative characterization by scanning microwave microscopy (SMM) of a live cell in its physiological buffer. The challenges for quantitative SMM of soft matter in liquid were overcome mainly by characterizing the probe–sample interaction through multiscale finite-element full-wave electromagnetic simulation of not only the probe tip but also the probe body and holder. Using quantitative SMM, the relative permittivity of the center of a live L6 cell on the top of its nucleus was determined to be ($32\pm 6)-j(20 \pm 4)$ , which was in general agreement with the literature and simple estimation. Moreover, taking advantage of the noninvasiveness and subsurface sensitivity of SMM, it was used to monitor the physiological condition of the cell for hours. The results showed that the gradual shrinking of the cell footprint did not impact cell vitality significantly. These results implied that SMM could be a valuable technique for label-free noninvasive characterization of subcellular structures in a live cell, as well as its physio-pathological conditions. [ABSTRACT FROM AUTHOR]

We propose a method to evaluate the electrical properties of nanoscale layered materials. This study is important for the potential application of these structures in light emitting diode electrodes. For this purpose we measure the reflection coefficient of a microwave signal recorded by a near-field Scanning Microwave Microscope. This method allows the non-contact measurement of the sheet resistance of the material under analysis. It provides detailed maps of the electrical properties of a micrometric area under test to assay its uniformity. In particular, we have applied this technique to a multilayer material composed by an Indium–Tin–Oxide film and few layer graphene. [ABSTRACT FROM PUBLISHER]

In this paper, we describe how to define and build a set of known loads to be used in near-field microwave microscopy. Such loads are necessary to set up a microwave calibration kit, enabling local quantitative measurements by the microscope. The proposed protocol is validated through the microscopy system we have recently developed that combines a scanning tunneling microscope and a 70-GHz vector network analyzer. [ABSTRACT FROM AUTHOR]