Probing liquid behaviour by helium atom scattering: surface structure and phase transitions of an ionic liquid on Au(111)

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

“…This can also be used to monitor thin film growth modes. 8,[84][85][86] and real time relaxation effects by monitoring changes in the Helium signal after the deposition has been completed, 87 see also specific science case Section 3.7.2. As mentioned in Section 1 HAS is particularly sensitive to light adsorbates, including hydrogen, which has been used in a large number of fundamental structure and dynamic studies, see for Table 1 The e-ph coupling constant l HAS as derived from the temperature dependence of the HAS elastic diffraction intensity for all simple metals that have been measured is shown in the next-to-last column.…”

Molecular scale structure and dynamics at an ionic liquid/electrode interface

“…In thin IL lms, long range ordered structures have been found by helium atom scattering. 25 Starting in 2010, initial attempts have been made to investigate the response of the interfacial structure to electrode potentials by XRR 26 and neutron reectivity. 27 However, in these early studies substrate reconstruction on gold surfaces 28 and a limited q-range in neutron reectivity rendered the extraction of the molecular-scale ion structure near the interface highly ambiguous.…”

Ionic liquid ultrathin films at the surface of Cu(100) and Au(111)

“…For example, knowledge of ionic behavior at a surface can be crucial for developing optimized electrolyte-electrode combinations in real life energy devices, and necessitates probing IL-metal interfaces at the Ångstrom level that are often obscured by a µm-thick IL layer. Reports on the IL organization within the bulk and at the gas-liquid interface are becoming more common, 3,[6][7][8][9][10][11][12][13][14][15][16][17][18] however, insights into this hidden interface have been more limited and often necessitate a surface science approach, using atomic force microscopy, 4,5,19 x-ray photoemission spectroscopy (XPS), [20][21][22][23][24][25][26][27] UV-photoemission spectroscopy (UPS), [27][28][29][30][31][32][33][34][35] inverse photoemission spectroscopy (IPS), 30 helium atom scattering, 36 or scanning tunneling microscopy (STM). 34,[37][38][39][40] The intrinsically low vapor pressure of most ionic liquids enables their use for controlled deposition of ultrathin films using physical vapor deposition (PVD) in ultrahigh vacuum (UHV).…”