Anomalous Lattice Dynamics ofEuSi2Nanoislands: Role of Interfaces Unveiled

Abstract

We report a systematic lattice dynamics study of EuSi_{2} films and nanoislands by in situ nuclear inelastic scattering on ^{151}Eu and ab initio theory. The Eu-partial phonon density of states of the nanoislands exhibits anomalous excess of phonon states at low and high energies, not present in the bulk and at the EuSi_{2}(001) surface. We demonstrate that atomic vibrations along the island-substrate interface give rise to phonon states both at low and high energies, while atomic vibrations across the island-island interface result in localized high-energy phonon modes.

Phonon confinement and spin-phonon coupling in tensile-strained ultrathin EuO films

“…This function accounts remarkably well for the phonon lifetime broadening that arises from strain-relaxation induced distribution of interatomic distances. 24,41 The relatively low value of Q indicates a residual epitaxial strain in the EuO films on YAlO 3 (110), which fully relaxes at a film thickness of about 38 nm. 30 In addition, Fig.…”

Lattice dynamics of epitaxial strain-free interfaces

“…Interface-specific vibrational phenomena such as phonon folding [17][18][19], localized vibrational modes [20], coherent phonon heat conduction [21], crossover from incoherent to coherent phonon scattering [22], and enhanced thermal conductivity [23,24] have experimentally been observed and theoretically studied. Yet, a comprehensive understanding of the lattice dynamics at the atomistic level even in the simplest case of a perfectly matched interface between dissimilar materials, leading, for example, to the Kapitza resistance [25,26], is still missing.…”

Phonon density of states in lanthanide-based nanocrystals

“…Theory predicts two effects in NCs: A phonon confinement gap purely related to the size of the NCs should appear [8] and the PDOS of NCs should feature enhanced tails at the low-and high-energy limits [35]. Indeed, the latter effects have been observed by nuclear-resonant inelastic x-ray scattering (NRIXS) of 57 Fe in several studies on transition-metal nanoparticles [36][37][38][39]. Non-resonant scattering techniques were recently applied to PbS (INS) [40] and PbTe NCs (IXS) [41].…”