Structural changes during the reaction of Ni thin films with (100) silicon substrates

Ultrathin films of nickel deposited onto (100) Si substrates were found to form kinetically constrained multilayered interface structures characterized by structural and compositional gradients. The presence of a native SiO2 on the substrate surface in tandem with thickness-dependent intrinsic stress of the metal film limits the solid-state reaction between Ni and Si. A roughly 6.5 nm thick Ni film on top of the native oxide was observed regardless of the initial nominal film thickness of either 5 or 15 nm. The thickness of the silicide layer that formed by Ni diffusion into the Si substrate, however, scales with the nominal film thickness. Cross-sectional in situ annealing experiments in the transmission electron microscope elucidate the kinetics of interface transformation towards thermodynamic equilibrium. Two competing mechanisms are active during thermal annealing: thermally activated diffusion of Ni through the native oxide layer and subsequent transformation of the observed compositional gradient into a thick reaction layer of NiSi2 with an epitaxial orientation relationship to the Si substrate; and, secondly, metal film dispersion and subsequent formation of faceted Ni islands on top of the native oxide layer

Equilibrium Shape of Crystals

This chapter discusses the equilibrium crystal shape (ECS) from a physical perspective, beginning with a historical introduction to the Wulff theorem. It takes advantage of excellent prior reviews, particularly in the late 1980's, recapping highlights from them. It contains many ideas and experiments subsequent to those reviews. Alternatives to Wulff constructions are presented. Controversies about the critical behavior near smooth edges on the ECS are recounted, including the eventual resolution. Particular attention is devoted to the origin of sharp edges on the ECS, to the impact of reconstructed or adsorbed surface phases coexisting with unadorned phases, and to the role and nature of possible attractive step-step interactions.Comment: Review from Handbook of Crystal Growth, Fundamentals, 2nd ed., T. Nishinaga, ed. (Elsevier, Amsterdam, 2015), vol. 1A (Thermodynamics and Kinetics), ch. 5, pp. 215-264; ISBN 9780444563699/eBook:9780444593764; http://www.sciencedirect.com/science/article/pii/B9780444563699000058. 26 figs., reformatted into Phys. Rev. style, 30 pages; slightly modified, alphabetized bibliography, inc. title

The equilibrium shape of nickel

The crystal shape of Ni particles, dewetted in the solid state on sapphire substrates, was examined as a function of the partial pressure of oxygen (P(O 2)) and iron content using scanning and transmission electron microscopy. The chemical composition of the surface was characterized by atom-probe tomography. Unlike other face-centered cubic (fcc) equilibrium crystal shapes, the Ni crystals containing little or no impurities exhibited a faceted shape, indicating large surface anisotropy. In addition to the {1 1 1}, {1 0 0} and {1 1 0} facets, which are usually present in the equilibrium crystal shape of fcc metals, high-index facets were identified such as {1 3 5} and {1 3 8} at low P(O 2), and {0 1 2} and {0 1 3} at higher P(O 2). The presence of iron altered the crystal shape into a truncated sphere with only facets parallel to denser planes. The issue of particle equilibration is discussed specifically for the case of solid-state dewetting

Orientation relationship of Cu crystals on the sapphire (10-10) m-plane and (10-12) r-plane

International audienc

Orientation Relationships of Copper Crystals on C-Plane Sapphire

International audienceCopper particles have been grown on sapphire (0 0 0 1) substrates by dewetting a copper film either in the solid or the liquid state.After equilibration the particles adopt different orientation relationships (ORs). Solid state dewetting produces a single OR:Cu(1 1 1)[-110]||Al2O3(0 0 0 1)[-1010]: In contrast, dewetting in the liquid state (followed by solid state equilibration) produces four additionalORs, Cu(1 1 1)[ -110]||Al2O3(0 0 0 1)[-21 10]; Cu(1 1 0)[-110]||Al2O3(0 0 0 1)[-21 10]; Cu(3 1 1)[011]||Al2O3(0 0 0 1)[-21 10 ]andCu(2 1 0)[0 0 1]||Al2O3(0 0 0 1) [-21 10]; which have been found to have a similar interfacial energy. All of the ORs observed in this studyare consistent with the Fecht and Gleiter lock-in model, from which one would expect that densely packed directions in the interfaceplane of the metal crystals will tend to align with relatively dense directions in the substrate surface. The change in alignment directionon the c-sapphire side of the interface, from Al2O3 -1010 for solid state dewetted samples to Al2O3 -21 10 for samples dewetted inthe liquid state, appears to be related to a reconstruction of the copper–c-sapphire interface that occurs at a temperature between those atwhich the two types of samples are processed

Orientation Relationships of Copper Crystals on C-Plane Sapphire

International audienceCopper particles have been grown on sapphire (0 0 0 1) substrates by dewetting a copper film either in the solid or the liquid state.After equilibration the particles adopt different orientation relationships (ORs). Solid state dewetting produces a single OR:Cu(1 1 1)[-110]||Al2O3(0 0 0 1)[-1010]: In contrast, dewetting in the liquid state (followed by solid state equilibration) produces four additionalORs, Cu(1 1 1)[ -110]||Al2O3(0 0 0 1)[-21 10]; Cu(1 1 0)[-110]||Al2O3(0 0 0 1)[-21 10]; Cu(3 1 1)[011]||Al2O3(0 0 0 1)[-21 10 ]andCu(2 1 0)[0 0 1]||Al2O3(0 0 0 1) [-21 10]; which have been found to have a similar interfacial energy. All of the ORs observed in this studyare consistent with the Fecht and Gleiter lock-in model, from which one would expect that densely packed directions in the interfaceplane of the metal crystals will tend to align with relatively dense directions in the substrate surface. The change in alignment directionon the c-sapphire side of the interface, from Al2O3 -1010 for solid state dewetted samples to Al2O3 -21 10 for samples dewetted inthe liquid state, appears to be related to a reconstruction of the copper–c-sapphire interface that occurs at a temperature between those atwhich the two types of samples are processed