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1991 | Buch

Electronic Processes on Semiconductor Surfaces during Chemisorption

verfasst von: T. Wolkenstein

Verlag: Springer US

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"Hands are useless if there are no eyes to see what is obvious." -M. V. Lomonosov Dear Reader, I invite you to open this book and step on the semiconductor surface, where the processes that form the subject of the book come into play. The surface of the semiconductor is attracting more and more interest among researchers, in fact researchers in two different fields. These are notably the physicists and engineers engaged in research in semi­ conductor physics and the making of semiconductor devices. The entire industry of semiconductor instruments hinges on the problem of the surface. The quality of semiconductor devices, whose use is growing steadily, depends essentially on the properties of the surface. The instability of these properties and their uncon­ trollable alterations with temperature and under the influence of environmental conditions result in a lack of stability in the performance of semiconductor devices, hence the high percentage of waste in their industrial production. The methods used in factory laboratories to prevent such waste are largely empirical. The properties of the surface, the nature of the physicochemical processes that take place on it, and the role of environmental factors still remain obscure. A major task of the semiconductor industry is to learn to control the properties of the surface.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Electrons and Holes in a Semiconductor
Abstract
All the macroscopic properties of crystals (semiconductors, for one) can be divided into two classes. To one class belong all properties that are determined by the periodicity of the crystal, and for which the defects present in any real lattice play the role of a small correction term. Such properties are known as structure-independent. The other c1ass contains properties determined by local violations of periodicity of the crystal lattice. In this case the defects are of paramount importance. Such properties are known as structure-sensitive.
T. Wolkenstein
Chapter 2. The Various Types of Adsorption
Abstract
As soon as a semiconductor is brought into contact with a gaseous medium, its surface begins to be covered by the molecules of the gas, i.e., adsorption has set in. The process ceases when an equilibrium between the surface and the gaseous phase is established, Le., when the number of molecules passing from the gaseous phase to the surface per unit time is equal (on the average) to the number of molecules leaving the surface for the gas over the same interval. The presence of the molecules adsorbed by the semiconductor surface changes the properties of the latter. Thus, adsorption is the agent by which the ambient acts on the surface and, indirectly, on some of the bulk properties of the semiconductor .
T. Wolkenstein
Chapter 3. Electron Transitions in Chemisorption
Abstract
As we have seen, various forms of chemisorption can transform into one another. In other words, a chemisorbed particle, while remaining in the adsorbed state, may change the character of its bond with the surface, i.e., may change from a state with one type of bond to a state with another. These transitions indicate that there is localization or localization of a free electron or hole at the adsorbed particle or in its neighborhood (see Figs. 2.7–2.12).
T. Wolkenstein
Chapter 4. The Interaction Of The Surface With The Bulk In A Semiconductor
Abstract
When we speak of the interaction of the surface of a crystal with its bulk, we mean the correlation between the properties of the bulk and surface. A number of surface properties, such as the chemisorptivity of the surface, the charge of the surface, and the reactivity of the chemisorbed partic1es, are determined, as we have seen, by the position of the Fermi level at the crystal surface. Here we will characterize the position of the Fermi level by the distance between the level and the bottom of the conduction band and denote this distance by ∈s. On the other hand, a number of bulk properties, such as the electrical conductivity of the crystal and the carrier recombination rate, are determined by the position of the Fermi level in the bulk, which we characterize by ∈v, where ∈v is the distance between the Fermi level and the bottom of the conduction band in the bulk of the crystal. There is a unique relationship between ∈s and ∈v
T. Wolkenstein
Chapter 5. The Catalytic Effect of a Semiconductor
Abstract
The technical applications of semiconductors are extremely varied. However, until recently physics ignored the use of semiconductors as catalysts of chemical reactions. Such typical semiconductors as cuprous oxide, zinc oxide, and vanadium pentoxide are at the same time typical catalysts. Semiconductors serve as catalysts for many chemical reactions, including oxidation and hydrogenation.
T. Wolkenstein
Chapter 6. Processes on a Real Surface
Abstract
As we know, the regularities in adsorption observed experimentally often deviate from those predicted by the classical Langmuir theory of adsorption. These deviations, which also arise both in adsorption kinetics and in adsorption equilibrium (non-Langmuir isotherms and the dependence of the differential adsorption heat on surface coverage), indicate the violation of one or more of the initial assumptions unnderlying Langmuir’s theory.
T. Wolkenstein
Chapter 7. The Effect of Illumination on the Adsorptive and Catalytic Properties of a Semiconductor
Abstract
It is now experimentally well established that illumination influences the adsorptive properties of a semiconductor surface. This phenomenon will be referred to as the photoadsorption effect. Illumination may influence both the adsorption equilibrium and the adsorption kinetics. Here we must distinguish between positive and negative photoadsorption effects.
T. Wolkenstein
Chapter 8. Adsorption and Luminescence
Abstract
Luminescence is always a sequence of two acts: in the first (endothermic) the system transforms from the ground state to an excited state (or from an excited state to a more excited state), and in the second (exothermic) it returns from the excited state to the ground state (or less excited state) accompanied by emission of aphoton.
T. Wolkenstein
Chapter 9. Conclusion
Abstract
The problem of the interaction of the gaseous phase with the lattice of asolid incorporates two types of problems. The first group consists of problems dealing with the interaction of an adsorbed particle with an adsorption center. Here both the electrons of the particles being adsorbed and those of the particle at which the adsorption takes place are involved. This group of problems is commonly known as the local interaction problem. But there are also entirely different problems, which chemists call problems of collective interaction. Here the interaction of the adsorbed particle with the entire lattice is studied, and the entire collection of free electrons and holes of the lattice come into play.
T. Wolkenstein
Metadaten
Titel
Electronic Processes on Semiconductor Surfaces during Chemisorption
verfasst von
T. Wolkenstein
Copyright-Jahr
1991
Verlag
Springer US
Electronic ISBN
978-1-4615-3656-7
Print ISBN
978-0-306-11029-0
DOI
https://doi.org/10.1007/978-1-4615-3656-7