Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.

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Alternative Plasmonic Materials: Beyond Gold and Silver

▪ Abstract Polycrystalline films have wide variety of applications in which their grain structures affect their performance and reliability. Thin film growth techniques and growth conditions affect grain shapes, the distribution of grain sizes, and the distribution of the crystallographic orientations of grains. Variations in these structural properties are affected by the conditions under which grain nucleation, growth, coarsening, coalescence, and thickening occur. General trends in structural evolution in polycystalline films, as a function of processing conditions and materials class, are discussed in terms of these fundamental kinetic processes.

Structure Evolution During Processing of Polycrystalline Films

A simple model for the formation of compressive stress in thin films by ion bombardment

This paper provides an overview on the current understanding of electromigration in metals. The discussion is first focused on studies in bulk metals and alloys. This part includes a thermodynamic formulation of electromigration, a kinetic analysis of the atomic processes and a review of the theory. In addition, experimental results in interstitial and substitutional systems are summarised. The second part of the paper reviews the studies in metallic thin films. This emerged as an important area of electromigration studies since the late 1960s when electromigration damage was found to cause failure of conductor lines in integrated circuits. The discussion will review first the basic nature of electromigration in thin films with emphasis on the role of grain boundaries in mass transport and damage formation. Then the materials issues of electromigration will be explored according to the scaling trends in VLSI technology. Finally, the recent results of electromigration in fine lines and device contacts of dimensions in the micrometre range are discussed.

https://iopscience.iop.org/article/10.1088/0034-4885/52/3/002/pdf

Electromigration in metals

A review of the sputtered film stress literature shows that the intrinsic stress can be tensile or compressive depending on the energetics of the deposition process. Modeling studies of film growth and extensive experimental evidence show a direct link between the energetics of the deposition process and film microstructure, which in turn determines the nature and magnitude of the stress. The fundamental quantities are the particle flux and energy striking the condensing film, which are a function of many process parameters such as pressure (discharge voltage), target/sputtering gas mass ratio, cathode shape, bias voltage, and substrate orientation. Tensile stress is generally observed in zone 1-type, porous films and is explained in terms of the grain boundary relaxation model, whereas compressive stress, observed in zone T-type, dense films, is interpreted in terms of the atomic peening mechanism. Modeling of the atomic peening mechanism and experimental data indicate that the normalized moment...

Intrinsic stress in sputter-deposited thin films

The kinetics of silicide growth are classified into three different categories: (a) diffusion controlled, (b) nucleation controlled, (c) others (reaction rate controlled). These are analyzed with the aim of understanding both the phenomenology of growth and the specific atomic mechanisms of phase formation. Diffusion-controlled growth is discussed with respect to the Nernst-Einstein equation. Stress relaxation is considered as a possible cause of reaction-rate control. The relative merits of two different types of marker experiments are compared. A few silicides are discussed in terms of what can be inferred about diffusion mechanisms. The competition between reaction-rate and diffusion control phenomena is shown to have specific effects on the sequence of phase formation; it is also related to the formation of some amorphous compounds. Reactions between silicon and alloyed metal films are used to illustrate the respective influences of mobility and driving force factors on the kinetics of silicide growth; they can also be used to underline the dominance of nucleation over diffusion in some silicide formation processes.

Kinetics of formation of silicides: A review

The reactions of metal layers with their silicon substrates resulting in the formation of various silicides are considered generally not only as phenomena common to all diffusion couples where new phases are formed, but also as typical of all transitions from two to three phases. The conditions under which such transitions will display the same characteristics as encountered in the usual one-to-two phase transitions (condensation, crystallization, boiling) are analyzed by comparison to the classical theory of nucleation. Because of the lack of knowledge about the exact values of the relevant parameters, the discussion is carried out mostly in descriptive thermodynamic terms. Although nucleation effects are analyzed in general terms, the main focus of attention is a class of reactions where nucleation dominates the formation of a new phase; a salient feature of these reactions is the absence of any equilibrium temperature, although the nucleation temperatures are relatively well defined within narrow limits. Nucleation effects are correlated to such material characteristics as the stability of the nucleated phases, and to such kinetic characteristics as the sequence of phase formation. The modification of the energy levels of the different phases brought about by stress, ion bombardment, or the replacement of usual phases by metastable ones, are considered with respect to their effect on nucleation processes. The nearly total absence of literature references to nucleation in metal-metal diffusion couples is discussed with respect to some specific aspects of the metal-silicon reactions.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400002557

Nucleation of a new phase from the interaction of two adjacent phases: Some silicides

Note on the origin of intrinsic stresses in films deposited via evaporation and sputtering

The formation of NiSi films from the reaction of Ni2Si with (100) and (111) silicon substrates was found to be controlled by a lattice diffusion process with an activation energy of 1.70 eV. In order to correlate kinetic information obtained by Rutherford backscattering with x‐ray diffraction data, ‘‘standard’’ diffraction powder patterns for both Ni2Si and NiSi have been established. The existence of a metastable hexagonal form of NiSi has been confirmed. Observations on the formation of Ni2Si confirm previous investigations. The diffusion process at work during the formation of NiSi is discussed in terms of the crystalline anisotropy of this compound and compared to what is known about diffusion in other silicides.

François M. d'Heurle

Papers

Kinetics of formation of silicides: A review

Nucleation of a new phase from the interaction of two adjacent phases: Some silicides

Note on the origin of intrinsic stresses in films deposited via evaporation and sputtering

Formation of thin films of NiSi: Metastable structure, diffusion mechanisms in intermetallic compounds

Formation of thin films of CoSi2: Nucleation and diffusion mechanisms