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.

Driven by interactions due to the charge, spin, orbital, and lattice degrees of freedom, nanoscale inhomogeneity has emerged as a new theme for materials with novel properties near multiphase boundaries. As vividly demonstrated in complex metal oxides and chalcogenides, these microscopic phases are of great scientific and technological importance for research in hightemperature superconductors, colossal magnetoresistance effect, phase-change memories, and domain switching operations. Direct imaging on dielectric properties of these local phases, however, presents a big challenge for existing scanning probe techniques. Here, we report the observation of electronic inhomogeneity in indium selenide (In2Se3) nanoribbons by near-field scanning microwave impedance microscopy. Multiple phases with local resistivity spanning six orders of magnitude are identified as the coexistence of superlattice, simple hexagonal lattice and amorphous structures with (almost equal to)100nm inhomogeneous length scale, consistent with high-resolution transmission electron microscope studies. The atomic-force-microscope-compatible microwave probe is able to perform quantitative sub-surface electronic study in a noninvasive manner. Finally, the phase change memory function in In2Se3 nanoribbon devices can be locally recorded with big signal of opposite signs.

The tremendous impact of electronic devices on our lives is the result of continuous improvements of the billions of nanoelectronic components inside integrated circuits (ICs). However, ultra-scaled semiconductor devices require nanometer control of the many parameters essential for their fabrication. Through the years, this created a strong alliance between microscopy techniques and IC manufacturing. This book reviews the latest progress in IC devices, with emphasis on the impact of electrical atomic force microscopy (AFM) techniques for their development. The operation principles of many techniques are introduced, and the associated metrology challenges described. Blending the expertise of industrial specialists and academic researchers, the chapters are dedicated to various AFM methods and their impact on the development of emerging nanoelectronic devices. The goal is to introduce the major electrical AFM methods, following the journey that has seen our lives changed by the advent of ubiquitous nanoelectronics devices, and has extended our capability to sense matter on a scale previously inaccessible.

Electromechanics combines processes from electrical and mechanical systems and focuses on their interactions, which lead to wide applications in modern electronics. The observation of microscale and nanoscale electromechanical phenomena is critical for understanding the underlying physics and inspiring scientific and technological innovations. Near-field scanning microscopy is a promising tool that utilizes evanescent waves to detect local physical properties at a length scale much smaller than the far-field resolution limit. This dissertation demonstrates the discoveries of novel electromechanical phenomena revealed by microwave impedance microscopy (MIM) and shows the invention and application of new scanning microwave microscopy technique inspired by the discoveries. In this dissertation, I first introduce the development of near field scanning probe microscopy. In Chapter 2, I begin by reviewing the basic components and the system design of microwave impedance microscopy (MIM), followed by a description of data analysis and its main application - local conductivity mapping. I then elaborate its other applications in the following chapters, categorized by the different properties probed by the technique. Chapter 3 demonstrates the discovery of a unique phonon mode existing in the ferroelectric domain walls. Chapter 4 shows a novel electromechanical transduction phenomenon in the ferroelectric domains of LiNbO3. In Chapter 5, I present the invention of a new microwave microscopy technique, transmission-mode MIM (T-MIM), which can be used to visualize the microwave field directly and has achieved great success on mapping surface acoustic wave (SAW). I conclude the thesis in Chapter 6 with a summary of the published discoveries and an outlook of the ongoing projects and future plans in this area

Near-field scanning microwave microscopy (NSMM) detects local physical properties of materials through electromagnetic interaction between the tip and the sample at a length scale much smaller than the freespace wavelength of the microwave radiation. However, previous implementations of NSMM have suffered from poor resolutions, low sensitivity, and unreliable tip-sample contact conditions. In this dissertation, I will first briefly review the prior research of NSMM (Chapter 1) and then naturally move on to the main theme — the basic principles and technical details of the recently developed microwave impedance microscope (MIM) (Chapter 2). I will present the development of MIM instrumentation including quantitative measurement with tuning-fork-based probes, broadband impedance microcopy, and implementation in cryogenic environment (Chapter 3), which are utilized in research described in the following chapters. The application of MIM will be demonstrated by a number of scientific studies in two general categories, emergent phenomena at ferroelectric domain walls and electrical inhomogeneity in nanodevices. Chapter 4 describes the discovery of low-energy structural dynamics of ferroelectric domain walls in hexagonal rare-earth manganites (h-RMnO3) by broadband impedance microscopy. Chapter 5 includes direct visualization of sketched conductive nanostructures at the LaAlO3/SrTiO3 heterostructure and nanoscale conductance evolution in ion-gel-gated oxide transistors, demonstrating the capability of MIM to image buried structures. I will conclude the dissertation with a short summary and outlook for the future.

Atomic force microscopy (AFM) can be used to analyze and measure the physical properties of all kinds of materials at nanoscale in the atmosphere, liquid phase, and ultra-high vacuum environment. It has become an important tool for nanoscience research. In this book, the basic principles of functional AFM techniques and their applications in energy materials—such as lithium-ion batteries, solar cells, and other energy-related materials—are addressed. FEATURES First book to focus on application of AFM for energy research Details the use of advanced AFM and addresses many types of functional AFM tools Enables readers to operate an AFM instrument successfully and to understand the data obtained Covers new achievements in AFM instruments, including electrochemical strain microscopy, and how AFM is being combined with other new methods such as infrared (IR) spectroscopy With its substantial content and logical structure, Atomic Force Microscopy for Energy Research is a valuable reference for researchers in materials science, chemistry, and physics who are working with AFM or planning to use it in their own fields of research, especially energy research.