arXiv subjects

Joseph R. Manson

Publications and source records attributed to Joseph R. Manson.

3 recordsLinked to original sources

arXiv2025

Observation of increasing bending rigidity of graphene with temperature

The mechanical properties of two-dimensional materials are important for a wide range of applications including composite and van der Waals-materials, flexible electronics and superconductivity. Several aspects are highly debated in the literature: For example, the theoretically predicted bending rigidity $κ$ at 0 K for quasi free-standing graphene varies from 0.8 to 1.6~eV, and there are predictions that it could either increase or decrease with temperature. Here we present an experimental study of the temperature-dependent bending rigidity $κ(T)$ of graphene. From the phonon dispersion relation measured with helium atom scattering for the out-of-plane acoustic (ZA) mode, we find $κ(T)$ to increase with sample temperature. We compare our experimental results with novel molecular dynamics (MD) simulations performed as part of this study as well as available literature data. The calculations reproduce the temperature trend of our experiments, but with a slightly weaker slope. A probable cause for the observed differences is the slight strain associated with experimental substrate supported graphene that is not present in the calculations.

cond-mat.mtrl-sci↗

arXiv2022

Observation of the Boson Peak in a 2D Material

The boson peak is an excess in the phonon density of states relative to the Debye Model, which occurs at frequencies below the Debye limit. It is present in most amorphous materials and, as was recently shown, can sometimes be found also in crystals. Here we present first experimental evidence of the boson peak in a 2D material, namely 2D silica (SiO$_2$). The measurements were obtained by helium atom scattering. A dispersionless boson peak is seen at $6 \pm 0.5$ meV (1.5$ \pm$ 0.15 THz) and $-6 \pm 1.5$ meV ($-1.5 \pm 0.4$ THz), with reasonable evidence for a double excitation at $\pm 12 \pm 2.5$ meV ($2.9 \pm 0.6$ THz).

cond-mat.mtrl-sci↗

arXiv2015

Ordered H2O Structures on a Weakly Interacting Surface, A Helium Diffraction Study of H2O/Au(111)

In this manuscript we report helium atom scattering (HAS) measurements of the structure of the first H2O layer on Au(111). The interaction between H2O and Au(111) is believed to be particularly weak and conflicting evidence from several indirect studies has suggested that water either grows as 3D ice crystals or as an amorphous wetting layer. In contrast, our measurements show that between 110K and 130K, H2O grows as highly commensurate well ordered islands which only partially wet the gold surface. The islands produce a clear (sqrt3Xsqrt3)R30 diffraction pattern and are characterized by a well defined height of ~ 5 Angstrom with respect to the surface gold atoms. These findings provide support for a unique double bilayer model which has recently been suggested for this surface.

cond-mat.mtrl-sci↗