The Electron-Phonon Interaction at Vicinal Metal Surfaces Measured with Helium Atom Scattering.

Recently, it was demonstrated that inelastic helium atom scattering from conducting surfaces provides a direct measurement of the surface electron-phonon coupling constant (mass enhancement factor ) via the temperature or the incident wave vector dependence of the Debye-Waller exponent. Here, previous published as well as unpublished helium atom scattering diffraction data from the vicinal surfaces of copper (Cu(11α), with α = 3, 5, 7) and aluminum (Al(221) and Al(332)) were analyzed to determine . The results suggested an enhancement with respect to the corresponding data for the low-index surfaces (111) and (001) above the roughening transition temperature.

Variation of bending rigidity with material density: bilayer silica with nanoscale holes.

Two dimensional (2D) materials are a young class of materials that is foreseen to play an important role as building blocks in a range of applications, flexible electronics. For such applications, mechanical properties such as the bending rigidity are important. Only a few published measurements of the bending rigidity are available for 2D materials.

Material properties particularly suited to be measured with helium scattering: selected examples from 2D materials, van der Waals heterostructures, glassy materials, catalytic substrates, topological insulators and superconducting radio frequency materials.

Helium Atom Scattering (HAS) and Helium Spin-Echo scattering (HeSE), together helium scattering, are well established, but non-commercial surface science techniques. They are characterised by the beam inertness and very low beam energy (<0.1 eV) which allows essentially all materials and adsorbates, including fragile and/or insulating materials and light adsorbates such as hydrogen to be investigated on the atomic scale.

The electron-phonon coupling constant for single-layer graphene on metal substrates determined from He atom scattering.

Recent theory has demonstrated that the value of the electron-phonon coupling strength λ can be extracted directly from the thermal attenuation (Debye-Waller factor) of helium atom scattering reflectivity. This theory is here extended to multivalley semimetal systems and applied to the case of graphene on different metal substrates and graphite. It is shown that λ rapidly increases for decreasing graphene-substrate binding strength.

The Electron-Phonon Interaction of Low-Dimensional and Multi-Dimensional Materials from He Atom Scattering.

Atom scattering is becoming recognized as a sensitive probe of the electron-phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye-Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials.