Adsorption and Growth of Cadmium on Polycrystalline Tungsten

Abstract

The multilayer adsorption and growth of cadmium on clean polycrystalline tungsten ribbons (with strong preferred orientation) has been investigated with a molecular-beam and mass-spectrometric technique. The adsorption and desorption kinetics have been studied as a function of temperature, supersaturation, and coverage. Five distinct adsorption states have been found between 100 and 600°C. Growth of bulk cadmium occurs only after multilayer adsorption is complete. No measurable supersaturation or critical nucleation event is observed for the growth of cadmium. However, even at high supersaturation and heavy coverage, the condensation coefficient is still smaller than unity. The kinetic and structural data are explained by the evolution of faceted, crystallographic, and epitaxial cadmium islands on the cadmium multilayer adsorbate.

Engineering the Microstructure and Morphology of Explosive Films via Control of Interfacial Energy

“…PETN films on low surface energy substrates are characteristic of 3D island growth, whereas films on high surface energy substrates indicate two-dimensional layer growth . This is consistent with early observations of surface contamination effects on inorganic polycrystalline film growth . However, in inorganic film growth, the influence of the substrate and interfacial conditions becomes insignificant for layer growth beyond a few hundred nanometers.…”

“…94 This is consistent with early observations of surface contamination effects on inorganic polycrystalline film growth. 95 However, in inorganic film growth, the influence of the substrate and interfacial conditions becomes insignificant for layer growth beyond a few hundred nanometers. In this study, substrate effects on PETN film growth were shown to persist for thicknesses greater than 10 μm.…”

“…In terms of substrate−vapor interactions, chemical reactions at the surface, as seen in CVD processes, would likely have a more pronounced effect on morphology evolution than intermolecular forces alone but were not considered in this study. The strength of intermolecular forces between the substrate and vapor, represented by the surface energy, has been shown to influence the growth modes and morphology in inorganic films 95 measure in situ, the surface energy of the substrate could be included as another independent parameter in improved SZMs. As discussed, especially for organic materials, the extent of influence from changes in surface energy likely depends on the degree of anisotropy in the crystal system and not necessarily in a monotonic fashion.…”

“…In terms of substrate–vapor interactions, chemical reactions at the surface, as seen in CVD processes, would likely have a more pronounced effect on morphology evolution than intermolecular forces alone but were not considered in this study. The strength of intermolecular forces between the substrate and vapor, represented by the surface energy, has been shown to influence the growth modes and morphology in inorganic films in addition to the PETN films of this study, yet are not considered in traditional SZMs. While difficult to measure in situ , the surface energy of the substrate could be included as another independent parameter in improved SZMs.…”

High-resolution characterization of TiN diffusion barrier layers

“…The layer growth mode is sustained provided there is a continuous decrease in bonding energy between the layers from the first monolayer to the bulk-crystal value [17,36]. A classic example of layer growth is contamination-free homoepitaxial growth of semiconductor films [40], but it also occurs when depositing a low-meltingpoint metal on a high-melting-point metal [41].  Stranski-Krastanov growth develops when layer growth becomes unfavorable after the formation of one or more monolayers and island growth proceeds.…”