1 Surface Physics in Tribology 1.1 Introduction 1.2 Geometry of Surfaces 1.3 Theoretical Considerations Surface Theory • Friction Fundamentals 1.4 Experimental Determinations of Surface Structure Low-Energy Electron Diffraction • High-Resolution Electron Microscopy • Field Ion Microscopy 1.5 Chemical Analysis of Surfaces Auger Electron Spectroscopy • X-ray Photoelectron Spectroscopy • Secondary Ion Mass Spectroscopy • Infrared Spectroscopy • Thermal Desorption 1.6 Surface Effects in Tribology Atomic Monolayer Effects in Adhesion and Friction • Monolayer Effects due to Adsorption of Hydrocarbons • Atomic Effects in Metal-Insulator Contacts 1.7 Concluding Remarks 1.1 Introduction Tribology, the study of the interaction between surfaces in contact, spans many disciplines, from physics and chemistry to mechanical engineering and material science, and is of extreme technological impor- tance. In this first chapter on tribology, the key word will be surface . This chapter will be rather ambitious in scope in that we will attempt to cover the range from microscopic to macroscopic. We will approach this problem in steps: first considering the fundamental idea of a surface, next recognizing its atomic character and the expectations of a ball model of the atomic structures present. We will then consider more realistic relaxed surfaces and then consider how the class of surface, i.e., metal, semiconductor, or insulator, affects these considerations. Finally, we will present what is expected when a pure material is alloyed and the effects of adsorbates. Following these more fundamental descriptions, we will give brief descriptions of some of the exper- imental techniques used to determine surface properties and their limitations. The primary objective here will be to provide a source for more thorough examination by the interested reader. Finally, we will examine the relationship of tribological experiments to these more fundamental atomistic considerations. The primary goals of this section will be to again provide sources for further study of tribological experiments and to raise critical issues concerning the relationship between basic surface properties with regard to tribology and the ability of certain classes of experiments to reveal the underlying interactions. We will attempt to avoid overlapping the material presented by other authors in this publication. This chapter cannot be a complete treatment of the physics of surfaces due to space Phillip B. Abel NASA Glenn Research Center John Ferrante Cleveland State University 2 Surface Roughness Analysis and Measurement Techniques 2.1 The Nature of Surfaces 2.2 Analysis of Surface Roughness Average Roughness Parameters • Statistical Analyses • Fractal Characterization • Practical Considerations in Measurement of Roughness Parameters 2.3 Measurement of Surface Roughness Mechanical Stylus Method • Optical Methods • Scanning Probe Microscopy (SPM) Methods • Fluid Methods • Electrical Method • Electron Microscopy Methods • Analysis of Measured Height Distribution • Comparison of Measurement Methods 2.4 Closure 2.1 The Nature of Surfaces A solid surface, or more exactly a solid–gas or solid–liquid interface, has a complex structure and complex properties depending on the nature of the solids, the method of surface preparation, and the interaction between the surface and the environment. Properties of solid surfaces are crucial to surface interaction because surface properties affect real area of contact, friction, wear, and lubrication. In addition to tribological functions, surface properties are important in other applications, such as optical, electrical and thermal performance, painting, and appearance. Solid surfaces, irrespective of their method of formation, contain irregularities or deviations from the prescribed geometrical form (Whitehouse, 1994; Bhushan, 1996, 1999a,b; Thomas, 1999). The surfaces contain irregularities of various orders ranging from shape deviations to irregularities of the order of interatomic distances. No machining method, however precise, can produce a molecularly flat surface on conventional materials. Even the smoothest surfaces, such as those obtained by cleavage of some crystals, contain irregularities, the heights of which exceed the interatomic distances. For technological applications, both macro- and micro/nanotopography of the surfaces (surface texture) are important (Bhushan, 1999a,b). In addition to surface deviations, the solid surface itself consists of several zones having physico- chemical properties peculiar to the bulk material itself ( Figure 2.1 ) (Gatos, 1968; Haltner, 1969; Buckley, 1981). As a result of the forming process in metals and alloys, there is a zone of work-hardened or Bharat Bhushan The Ohio State University © 2001 by CRC Press LLC . 1 Surface Physics in Tribology 1. 1 Introduction 1. 2 Geometry of Surfaces 1. 3 Theoretical Considerations Surface Theory • Friction Fundamentals 1. 4 Experimental Determinations. (Gatos, 19 68; Haltner, 19 69; Buckley, 19 81) . As a result of the forming process in metals and alloys, there is a zone of work-hardened or Bharat Bhushan The Ohio State University © 20 01 by CRC. irregularities or deviations from the prescribed geometrical form (Whitehouse, 19 94; Bhushan, 19 96, 19 99a,b; Thomas, 19 99). The surfaces contain irregularities of various orders ranging from shape