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Skickas inom vardagar. Laddas ned direkt. The goal of this book is to provide a general overview of the rapidly developing field of novel scanning probe microscopy SPM techniques for characterization of a wide range of functional materials, including complex oxides, biopolymers, and semiconductors.
Many recent advances in condensed matter physics and materials science, including transport mechanisms in carbon nanostructures and the role of disorder on high temperature superconductivity, would have been impossible without SPM. The unique aspect of SPM is its potential for imaging functional properties of materials as opposed to structural characterization by electron microscopy.
Examples include electrical transport and magnetic, optical, and electromechanical properties. By bringing together critical reviews by leading researchers on the application of SPM to to the nanoscale characterization of functional materials properties, this book provides insight into fundamental and technological advances and future trends in key areas of nanoscience and nanotechnology.
In AFM, the interaction force between the tip and sample surface is used as a control signal to allow visualization of structures at the nanoscale. This method may be used to observe a wide range of nanomaterials, including insulators and materials containing biomolecules. SPM allows the functions and physical properties of materials to be measured at the nanoscale. Many specialized analysis modes have been developed, allowing investigation of not only the morphology and atomic structure, but also mechanical properties, electrical properties, magnetic properties, and various other nanoscale physical properties.
Many of the functions exhibited by nanomaterials arise from quantum effects, requiring an understanding of novel electronic states arising due to closed nanoscale structures or reduced dimensionality. STM is the most powerful spectroscopic visualization method for electronic states.
The tunneling current I can then be expressed as the convolution of the tip profile with the sample LDOS. Applying a two-dimensional fast Fourier transform FFT to the LDOS image allows visualization of physical properties in k -space, such as the reciprocal lattice, the lowerdimensional Fermi surface, and the band structure. As the miniaturization of semiconductor devices such as CMOS FETs proceeds, the ability to obtain detailed information on electronic states including band bending in the vicinity of single dopant atoms in conducting channels will yield important insights for electronic device development.
Similarly, the use of spinpolarized electrons in STS allows surface magnetic properties to be analyzed with atomic resolution, aiding the development of spintronic devices and nanomagnetic materials. To develop these techniques further as tools for studying physical properties and function will require working conditions in which quantum effects are clearly discernible, including ultra-low temperatures, high magnetic fields, and ultra-high vacuums, pushing environmental control requirements to extreme limits.
SPM not only makes possible a rich selection of atomic scale measurements, but can also be used to perform a variety of nanofabrication tasks, including manipulation of single atoms.
The wide range of measurable physical quantities that can be observed via SPM methods — which includes the density of states, near-field light, spin polarization, inelastic tunneling spectroscopy, the local work function, electric potentials, and magnetic and mechanical properties — testifi es to the broad usefulness of SPM techniques. Examples of the extensive variety of ways in which SPM can be used for nanofabrication include single-atom manipulation, nanoscale molding and forming, selective local oxidation, nanolithography, and tip mass transport.
Thus, SPM methods offer extremely powerful capabilities for both nanoscale fabrication and many types of high-resolution measurements in actual operating environments. SPM nanoscale measurement techniques, the foundation on which nanotechnology is built, can be divided into two categories Figure 2.
The first class of methods combines nanofabrication and nanoscale measurements into a paradigm inspired by the notion that Scanning is creating. In this approach, stress, temperature, pressure, vacuum level, radiation, and other environmental conditions are tightly interwoven with the material fabrication process. A second class of methods consists of multifaceted operando nanoscale measurements, performed within the functional expression environment, with the goal of elucidating the mechanisms of functional expression — a strategy we might term the Seeing is discovering approach.
Many nanomaterial functions arise from quantum effects that emerge prominently under circumstances that are extreme in multiple ways: ultra-low temperatures, high magnetic fields, ultra-high vacuums, or similar environments. Ultra-low temperatures suppress thermal fluctuations, allowing the observation of quantum effects involving electrons. Phenomena that may be observed under such conditions include interference among low-dimensional electron waves, single-electron effects, and inelastic tunneling. Strong magnetic fields play an important role in studies on spin effects, superconductivity, Landau quantization, and other similar phenomena.
Thus, SPM operando nanoscale measurement is a technique for analyzing surface behavior in "living" samples. Within the nanotechnology sector, strategies for meeting the dual needs of nanofabrication and direct characterization are essential. These include the fusion of nanofabrication and in-situ nanoscale measurements: nanostructure fabrication by tip induction, control of surface structure via control of injected electron energy, singleatom manipulation, fabrication of low-dimensional quantum nanostructures, and manipulation of nanoclusters.
An important breakthrough demonstrating the achievement of atomic-level manipulation was the world's first successful reversible manipulation of one-dimensional periodic structures on a Si surface — a staple semiconductor material — by controlling the energy of carriers injected from a probe tip Figure 3.
Scanning Probe Microscopy of Functional Materials. Nanoscale Imaging and Spectroscopy. Editors: Kalinin, Sergei V., Gruverman, Alexei (Eds.) Free Preview. Request PDF on ResearchGate | Scanning Probe Microscopy of Functional Materials: Nanoscale Imaging and Spectroscopy | Novel scanning probe microscopy.
Moreover, by combining this idea with a method for transferring individual atoms from a probe tip to a surface, we developed a technique for inducing a closing off — within a nanoscale region — of the one-dimensional surface electronic states formed by an array of Si dimers, due to the potential barrier created by the transferred atom. For this experiment, we fabricated a one-dimensional quantum well structure based on a Si dimer array at an atomic level, and developed a LDOS imaging technique to visualize the quantized energy levels inside the quantum well.
Superstructure control is achieved by controlling the energy of electrons or holes injected into the dimer. The environmental conditions that are important for materials research include temperature, needed to characterize properties such as the thermal resistance of materials; the gas atmosphere, needed to characterize catalytic materials and other substances; stress, needed to control physical properties by inducing lattice distortion; and inert-gas environments, needed to characterize materials for batteries. The development of SPM measurement techniques with environmental control related to innovations in materials is already underway.
Examples include a atomic-resolution SPM methods in high-temperature gas environments, and b atomic-resolution SPM methods under externally controlled stress fields. The stability of ultra-thin oxide layers on semiconductor surfaces is important for industrial applications, and phenomena such as high-temperature decomposition of SiO 2 thin films have been studied using methods such as low-energy electron microscopy LEEM.
Although STM is a powerful tool for atomic-resolution observations at high temperatures and under ultra-high vacuums, the fact that SiO 2 thin films are electrically insulating makes STM difficult to apply to films with thicknesses of greater than 2 nm. On the other hand, high-temperature noncontact AFM NCAFM measurements of insulating surfaces using standard cantilever tips suffer from the difficulty that, because the surface and the sensor lever are in close proximity, thermal radiation effects become prominent, preventing this approach from offering adequate performance.
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