This chapter is a brief overview of the physics governing processes at the nanoscale. We are used to the macroscopic world and have developed an understanding, based on what is usually called “classical physics” of the behavior of the objects that we see with our eyes. However, classical physics is not able to explain certain phenomena occurring at the atomic or molecular level or below. Compared to macroscopic systems, quantum effects can become important and certain classical physical effects, which are negligible for macroscopic objects, can become prominent. We present here some new aspects showing how nano-objects behave compared to what is expected by extrapolating our knowledge on macroscopic systems. Further items will be introduced in the subsequent chapters when needed. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
This chapter is a brief overview of the physics governing processes at the nanoscale. We are used to the macroscopic world and have developed an understanding, based on what is usually called “classical physics” of the behavior of the objects that we see with our eyes. However, classical physics is not able to explain certain phenomena occurring at the atomic or molecular level or below. Compared to macroscopic systems, quantum effects can become important and certain classical physical effects, which are negligible for macroscopic objects, can become prominent. We present here some new aspects showing how nano-objects behave compared to what is expected by extrapolating our knowledge on macroscopic systems. Further items will be introduced in the subsequent chapters when needed. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Chapter 3 provides a brief review of a few concepts from classical Newtonian physics, and how this fails to explain phenomena at the nanoscopic scale. As is detailed within, the classical mechanical model is able to describe all observed physical phenomena; however, when it comes to the nanoscale this model breaks down, because the properties of the materials change dramatically. At this scale, the surface-to-volume ratio increases, gravitational forces become negligible and random molecular motion becomes more important. This changes the properties of the material and affects the devices that are fabricated at this scale. It is hence necessary to develop a new model that can explain such physical phenomena. This has led to a new branch of physics, i.e. quantum physics (QP) or quantum mechanics, which is able to explain the behavior observed at nanoscale. QP enables us to explain phenomena such as the photoelectric effect, Compton effect. etc. In this chapter, we introduce quantum mechanics and how it evolved in the late 19th and early 20th centuries. Further, light’s behaviour as a particle as well as a wave is described by the photoelectric effect and Young’s double-slit experiment, respectively. Further, the dual nature of the particle is explained using the de Broglie principle. Schrodinger’s equation is then explained, which gives the probability of finding a subatomic-scale particle at a certain position in a quantum well. In addition to the formulation of Schrodinger’s equation, its solution, the concept of a potential well, the characteristics of the wave function and its interpretation and significance, and, finally, the application of Schrodinger’s equation in the structure of an atom form subsequent parts of this chapter. The equation serves as a basis with which to understand band theory. Band theory explains the difference between conductors, insulators and semiconductors. Materials are distinguished according to the differences in their band gaps. Adding impurities or varying temperature changes the band gap in semiconductors, which consequently changes the properties of the semiconductor and its electrical conduction. One more important measure to understand and exploit the properties and behaviour of materials is Fermi–Dirac statistics. It is useful to acquire the probability of electrons at a given energy level at a specific temperature. These concepts can be utilised by physicists and chip makers to make more energy-efficient devices. Hence, this chapter details the fundamentals of quantum physics and how they relate to the electrical properties of nanodevices.
One of the basic objectives in the foundations of physics is to understand the detailed circumstances of the transition from pure quantum effects to classical appearances. This field has gained an even increased attention because of the fact that quantum phenomena on the mesoscopic or even macroscopic scale promise to be useful for future technologies, such as in lithography with clusters and molecules, quantum computing or highly sensitive quantum sensors. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
An outline is given of the interpretation of quantum mechanical expressions if one assumes that what is called Quantum Mechanics today, refers to an underlying reality as in Chap. 2 , even if many authors claim to have evidence to the contrary, as is usually brought forward. If there exists a sub-microscopic classical world of real things, is that the same classical world as the world of large things such as planets, rocks and people? How does the notion of probability enter into quantum mechanics? These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Introduction The evolution of microelectronics toward reduced device sizes has proceeded to a degree that renders conventional models, approaches, and theories inapplicable. Indeed, for objects with sizes of 100 nanometers or less it is frequently the case that the length scales associated with fundamental physical processes are comparable to the geometrical size of the device; also, fundamental time scales associated with physical processes are of the order of the time parameters for nanodevice operation. Therefore, on the nanoscale the theories and models underlying modern nanoelectronics become more complicated, and rely more and more on basic science. Generally, in the nanoworld the fundamental laws of physics that govern particles and material fields differ from those that apply to familiar macroscopic phenomena such as the motion of a baseball or a train. Instead of classical mechanics, that works so well for macroscopic phenomena, the motion of particles in the nanoworld is determined by the so-called wave mechanics or quantum mechanics. An underlying principle of central importance for nanophysics is the fundamental concept that all matter , including electrons, nuclei, and electromagnetic fields, behaves as both waves and particles , that is, wave–particle duality is a basic characteristic of all matter. At first glance, wave properties and particle properties for the same physical object are hardly compatible. To understand wave–particle duality, we will briefly review, in the following two subsections, the basic properties of particles and waves known from classical physics.
Both classical and quantum principles coexist in the mesoscopic world, something between the microscopic and the macroscopic worlds.More precisely, mesoscopic physics studies how the "coherence", which governs the wave property and especially the interference effect of matter, disappear gradually as the scale increases from the microscopic to the macroscopic scale.Another important issue in mesoscopic physics is many-body effects, which originate from the interaction among electrons.Many-body effects are a fundamental issue in all modern physics, but mesoscopic physics is particularly well adopted for their study because mesoscopic systems allow for tunability of various parameters, which is not possible in bulk systems.Further, the interplay between coherence and many-body effects leads to rich physical phe-