Lattice dynamics in Sn nanoislands and cluster-assembled films

Abstract

To unravel the effects of phonon confinement, the influence of size and morphology on the atomic vibrations is investigated in Sn nano islands and cluster-assembled films. Nuclear resonant inelastic X-ray scattering is used to probe the phonon density of states of the Sn nanostructures which show significant broadening of the features compared to bulk phonon behaviour. Supported by ab initio calculations, the broadening is attributed to phonon scattering and can be described within the damped harmonic oscillator model. Contrary to the expectations based on previous research, the appearance of high-energy modes above the cut-off energy is not observed. From the thermodynamic properties extracted from the phonon density of states, it was found that grain boundary Sn atoms are bound by weaker forces than bulk Sn atoms.

The influence of phonon softening on the superconducting critical temperature of Sn nanostructures

“…Phonon density of states. We have studied the PDOS of different Sn nanostructures by nuclear resonant inelastic X-ray scattering 32 and compared them to the PDOS of a bulk Sn foil. We found a decrease of high-energy phonon modes, a small enhancement of low-energy phonon modes and a general broadening of the PDOS features, see Fig.…”

“…5 and ref. 32 for a more thorough discussion of the PDOS measurements. These observations can www.nature.com/scientificreports www.nature.com/scientificreports/ be attributed to the high density of grain boundaries in the investigated nanostructures.…”

“…In this work, we determine the superconducting properties of different Sn nanostructures using the ADMM formalism, from the PDOS extracted earlier 32 from nuclear resonant inelastic X-ray scattering measurements.…”

Experimental observation of electron-phonon coupling enhancement in Sn nanowires caused by phonon confinement effects

“…Phonon softening specially affects nanoscale materials because the ratio of surface to volume atoms is higher than in bulk. These surface atoms are characterized for having lower vibrational frequencies than the bulk ones, known as surface modes [45,46], which shifts the phonon spectrum to the low energy region. While T c and λ e−ph increase monotonically as the diameter is reduced, it is not the case for ω 2 1/2 .…”

Nanoscale Hierarchical Structure of Twins in Nanograins Embedded with Twins and the Strengthening Effect

“…In addition to the mechanical properties, there are numerous reports on effects of nanoscale structure on fundamental properties of the material, such as, superconductivity observed in nanostructured HgBa 2 CuO 4 + y [16], La 2 CuO 4 + y [17], and Au-Ag [18]. The phonon density of states of Sn films are reported to be affected by the morphology and grain sizes in nanoscale [19]. Furthermore, electrodeposition is an effective method to control the structures in nanoscale [20].…”