A new compilation, based on a literature search for the period 1969–1976, is made of experimental data on the work function. For these 44 elements, preferred values are selected on the basis of valid experimental conditions. Older values, which are widely accepted, are given for 19 other elements on which there is no recent literature, and are so identified. In the data for the 63 elements, trends that occur simultaneously in both the columns and the rows of the periodic table are shown to be useful in predicting correct values and also for identifying questionable data. Several illustrative examples are given, including verifications of predictions published in 1950.

The work function of the elements and its periodicity

The mechanical properties of thin films on substrates are described and studied. It is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture to occur. It is argued that the approaches that have proven useful in the study of bulk structural materials can be used to understand the mechanical behavior of thin film materials. Understanding the mechanical properties of thin films on substrates requires an understanding of the stresses in thin film structures as well as a knowledge of the mechanisms by which thin films deform. The fundamentals of these processes are reviewed. For a crystalline film on a nondeformable substrate, a key problem involves the movement of dislocations in the film. An analysis of this problem provides insight into both the formation of misfit dislocations in epitaxial thin films and the high strengths of thin metal films on substrates. It is demonstrated that the kinetics of dislocation motion at high temperatures are expecially important to the understanding of the formation of misfit dislocations in heteroepitaxial structures. The experimental study of mechanical properties of thin films requires the development and use of nontraditional mechanical testing techniques. Some of the techniques that have been developed recently are described. The measurement of substrate curvature by laser scanning is shown to be an effective way of measuring the biaxial stresses in thin films and studying the biaxial deformation properties at elevated temperatures. Submicron indentation testing techniques, which make use of the Nanoindenter, are also reviewed. The mechanical properties that can be studied using this instrument are described, including hardness, elastic modulus, and time-dependent deformation properties. Finally, a new testing technique involving the deflection of microbeam samples of thin film materials made by integrated circuit manufacturing methods is described. It is shown that both elastic and plastic properties of thin film materials can be measured using this technique.

Mechanical properties of thin films

Atomic-scale control and manipulation of the microstructure of polycrystalline thin films during kinetically limited low-temperature deposition, crucial for a broad range of industrial applications, has been a leading goal of materials science during the past decades. Here, we review the present understanding of film growth processes—nucleation, coalescence, competitive grain growth, and recrystallization—and their role in microstructural evolution as a function of deposition variables including temperature, the presence of reactive species, and the use of low-energy ion irradiation during growth.

Microstructural evolution during film growth

Ultrathin metal films and particles on oxide surfaces: structural, electronic and chemisorptive properties

Surface studies of supported model catalysts

Growth structure investigation of MgF2 and NdF3 films grown by molecular beam deposition on CaF2(111) substrates

Computer simulation of the post-nucleation growth of thin amorphous germanium films

The very early stage of formation of amorphous germanium films by vapour deposition is simulated. A simplified model is considered. In the post-nucleation stage particles are formed by an atom-by-atom building process. Re-evaporation of adatoms and migration along the edge of already formed particles are taken into account. An upper limit is obtained for the maximum edge migration distance for which irregularly shaped particles can still be formed within our model. From the results it is concluded that, during the formation of thin evaporated amorphous germanium films which show a supernetwork with irregularly shaped particles of high density, self-surface diffusion or diffusion along the edge of a particle cannot be significant.

Péter B. Barna

Papers

Growth structure investigation of MgF2 and NdF3 films grown by molecular beam deposition on CaF2(111) substrates

Computer simulation of the post-nucleation growth of thin amorphous germanium films

Computer simulation of the post-nucleation growth of thin amorphous germanium films.

Intermetallic phase formation in aluminium and iron thin film systems

Some remarks on the epitaxial growth of films on substrates coated with amorphous deposits