Atomic Geometry and Electronic Structure of Solid Surfaces

In this, the last major chapter of the book, we turn our attention to the applications of modern electronic structure models and concepts to more general geochemical problems; namely, those described by Goldschmidt as being concerned with the “distribution of elements in the geochemical spheres and the laws governing the distribution of the elements” (see Preface). The majority of minerals and rocks originally formed by crystallization from melts, and so the first section of this chapter is devoted to considering the nature of melts (and glasses), structure and bonding in melts, and the partitioning of elements (particularly transition elements) between the melt and crystallizing solid phases. The classic work of Bowen (1928) led to the recognition of particular sequences of crystallization and crystal-melt reaction relationships in the silicate melts from which major rock types form, as enshrined in the “Bowen Reaction Series.” Attempts were also made to explain the incorporation of particular elements into particular mineral structures using simple crystal chemical arguments, notably as laid down in “Goldschmidt’s Rules” (Goldschmidt, 1937). Such concepts are reappraised in the light of modern electronic structure theories. The other major realm of formation of minerals and rocks, and the most important medium of transport and redistribution of the chemical elements at the Earth’s surface, is the aqueous solution. The molecular and electronic structures of aqueous solutions, their behavior at elevated temperatures, formation and stabilities of complexes in solution, and the mechanisms of reactions in solution are all considered in the second section of this chapter. The surfaces of minerals (or other crystalline solids) differ from the bulk material in terms of both crystal structure and electronic structure. A great variety of spectroscopic, diffraction, scanning, and other techniques are now available to study the nature of solid surfaces, and models are being developed to interpret and explain the experimental data. These approaches are discussed with reference to a few examples of oxide and sulfide minerals. Although relatively few studies have been undertaken specifically of the surfaces of minerals, many of the reaction phenomena that occur in natural systems take place at mineral surfaces, so that such surface studies represent an important area of future research.

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The Electronic Structure of Solid Surfaces: Core Level Excitation Techniques

Journal of Vacuum Science and Technology ◽

10.1116/1.1317932 ◽

1973 ◽

Vol 10 (1) ◽

pp. 176-182 ◽

Cited By ~ 35

Author(s):

Robert L. Park ◽

J. E. Houston

Keyword(s):

Electronic Structure ◽

Core Level ◽

Solid Surfaces ◽

Excitation Techniques

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Self-Consistent Electronic Structure of Solid Surfaces

Physical Review B ◽

10.1103/physrevb.6.2166 ◽

1972 ◽

Vol 6 (6) ◽

pp. 2166-2177 ◽

Cited By ~ 228

Author(s):

J. A. Appelbaum ◽

D. R. Hamann

Keyword(s):

Electronic Structure ◽

Solid Surfaces ◽

Self Consistent

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EELS Measurement of the Local Electronic Structure of Copper Atoms Segregated to Aluminum Grain Boundaries

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164179 ◽

1996 ◽

Vol 54 ◽

pp. 342-343

Author(s):

S.J. Splinter ◽

J. Bruley ◽

P.E. Batson ◽

D.A. Smith ◽

R. Rosenberg

Keyword(s):

Electronic Structure ◽

Grain Boundaries ◽

Boundary Segregation ◽

Thin Layers ◽

Nominal Composition ◽

Spatially Resolved ◽

Service Lifetime ◽

Heat Treated ◽

Probe Size ◽

Local Electronic Structure

It has long been known that the addition of Cu to Al interconnects improves the resistance to electromigration failure. It is generally accepted that this improvement is the result of Cu segregation to Al grain boundaries. The exact mechanism by which segregated Cu increases service lifetime is not understood, although it has been suggested that the formation of thin layers of θ-CuA12 (or some metastable substoichiometric precursor, θ’ or θ”) at the boundaries may be necessary. This paper reports measurements of the local electronic structure of Cu atoms segregated to Al grain boundaries using spatially resolved EELS in a UHV STEM. It is shown that segregated Cu exists in a chemical environment similar to that of Cu atoms in bulk θ-phase precipitates.Films of 100 nm thickness and nominal composition Al-2.5wt%Cu were deposited by sputtering from alloy targets onto NaCl substrates. The samples were solution heat treated at 748K for 30 min and aged at 523K for 4 h to promote equilibrium grain boundary segregation. EELS measurements were made using a Gatan 666 PEELS spectrometer interfaced to a VG HB501 STEM operating at 100 keV. The probe size was estimated to be 1 nm FWHM. Grain boundaries with the narrowest projected width were chosen for analysis. EDX measurements of Cu segregation were made using a VG HB603 STEM.

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Electronic structure studies of conducting polymers by electron energy-loss spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163265 ◽

1996 ◽

Vol 54 ◽

pp. 160-161

Author(s):

J. Fink

Keyword(s):

Electronic Structure ◽

Conducting Polymers ◽

Conjugated Polymers ◽

Electron Acceptors ◽

Electron Donors ◽

Light Emitting ◽

One Dimensional ◽

New Class ◽

Electrical Conductivities ◽

Electron Energy Loss

Conducting polymers comprises a new class of materials achieving electrical conductivities which rival those of the best metals. The parent compounds (conjugated polymers) are quasi-one-dimensional semiconductors. These polymers can be doped by electron acceptors or electron donors. The prototype of these materials is polyacetylene (PA). There are various other conjugated polymers such as polyparaphenylene, polyphenylenevinylene, polypoyrrole or polythiophene. The doped systems, i.e. the conducting polymers, have intersting potential technological applications such as replacement of conventional metals in electronic shielding and antistatic equipment, rechargable batteries, and flexible light emitting diodes.Although these systems have been investigated almost 20 years, the electronic structure of the doped metallic systems is not clear and even the reason for the gap in undoped semiconducting systems is under discussion.

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