This course provides an introduction to experimental and theoretical study of the surfaces of solids. The purpose of the course is to represent the surface as an especially important object for physical investigation. It reviews a number of experimental techniques focusing on such modern methods as ARPES, STM/STS/AFM, LEED and their experimental requirements (UHV, synchrotron radiation, etc.). The theoretical and numeric approaches to describe the electronic structure and properties of surface and interfaces are considered on the basis of band theory of crystals.
The course is intended for 5 year graduate students (M.Sc.) interested in condenses matter experiment and theory. Required background: basic courses of quantum mechanics and the theory of solids.
Course outline:
Introduction to surface physics (2 h).
The surface as an especially important object for physical investigation. Influece of the surface on physical properties of objects. Clean and covered surfaces. Adsorbtion and catalysis. What is UHV: Vacuum concepts and UHV hardware. The methods to get clean surfaces. The structure of surfaces. Short overview of modern experimental techniques.
ARPES as the most direct method to visualize electronic structure of crystal surface. Electrons in crystals, how we see them: 3D momentum-energy space of electronic states of surfaces and 2D systems. Photoemission process. Electron analyzer's principles. Navigation in k-space. One particle spectral function. Concept of quasiparticles.
Basics of solid state physics (4 h).
Electrons in crystals: general principles. Drude model. Electroconductivity. Hall effect. Sommerfeld model. Electrons in crystal field: Bloch theorem. Semiclasical model. The reciprocal space: Brillouin zone, quasi-momentum, electronic bands. Effect of external factors: temperature, electric and magnetic fields.
Numerical methods to calculate electronic band structure (4 h).
Nearly-free electron approximation. Tight-binding model. KKR model. Pseudo-potential. Density-functional theory. Examples of band structure calculation in transition metals. Electronic density of states (DOS).
Electronic structure of low-dimensional systems (2 h).
DOS and dimensionality. Quantum walls and quantum dots. Lasers on heterostructures. Charge density waves (CDW) in quantum corals: quantum interference. Scanning tunneling spectroscopy (STS) and Fourier transform (FT) of its images. Relation between FT STS and autocorrelated electronic structure.
Work function (4 h).
Jelly model: taking into account Coulomb and exchange correlations. Double charged layer. Image potential. Effect of surface structure - Smoluchowski's concept of the surface double layer. Modification of crystal potemtial. Influence of the adsorbed atoms. Surface states of the adsorbed atoms. Experimental techniques to measure work function: photoemission, thermo electron emission, electron field microscope.
Electronic structure of surface (4 h).
Two approaches to qualitative description of the surface bands: nearly-free electron approximation and tight-binding model. Break down of the translational symmetry on the surface: surface states of a 3D crystal. Shockley states and Tamm states: different mathematical approaches. Proection of bulk band structure into surface Brillouine zone. Surface states in metals. Surface states in semiconductors. Surface resonances in metals. Manifestation of the surface states in electronic spectra.
Surface structure (4 h).
Crystal structures: examples. Miller index notation. Coordination number. Surface energy. Clean surfaces. Relaxation and reconstruction. Superstrucrures on Si surface: examples. Classification of ordered surface structures. STM, AFM, LEED, HREED and other experimental techniques for surface structure investigation. Symmetry in 2D lattice. Qusicrystals.
Crystal growth (2 h).
Surface thermodynamics - Gibbs treatment of the interfacial energy. Activation energy. Supercooling and oversaturation. Theories of nucleation. Crystal growth dynamics. Models of snow crystallization. Dislocational growth. The techniques to grow single crystals and and single crystalline films.
Physicochemical properties of surfaces (4 h).
The solid-gas interface. The surface area of solids. Surfaces as having fractal geometry. Adsorption. The adsorption time. The Langmuir adsorption isotherm. Experimental applications of the Langmuir equation. The BET and related isotherms. Chemisorption and catalysis. Chemical reactions on surface. Corrosion. Absorption: surface diffusion. Desorption. Sorption-desorption hysteresis on porous surfaces. Applications: absorbents, heterogeneous catalysis, adsorbtional cooling, surface amplified optical spectroscopy. Phase transitions on clean and covered surfaces.
Concluding lecture (2 h).
Analysis of possibilities and limitations of experimental and theoretical methods of study of electronic structure of surfaces. Looking for a comprehensive approach for manufacturing the adsorption systems with controlled electronic properties.
To read:
A. Zangwill. Physics at Surfaces - Cambridge University Press, 1988, 454 pages,
M. Prutton. Introduction to Surface Physics. - Oxford University Press,1994, 210 pages.
Surface and Thin Film Analysis: Principles, Instrumntation, Applications / Edited by H. Bubert and H. Jenett. - Wiley-VCH Verlag, 2002.
G. D. Billing. Dynamics of molecule surface interactions. - John Wiley & Sons, Inc., 2000.
V. V. Nemoshkalenko, V. N. Antonov. Computational Methods in Solid State Physics - CRC Press, 1998, 254 pages.
N. W. Ashcroft, N. D. Mermin, Solid State Physics. V. 1. - Holt, Rinehart and Winston, 1976, 848 pages.
R. Penrose. The Emperor's new mind - Oxford University Press, 1989.