He/Ar-atom scattering from molecular monolayers: C₆₀/Pt(111) and graphene/Pt(111)

Abstract

Supersonic He and Ar atomic beam scattering from C(60) and graphene monolayers adsorbed on a Pt(111) surface are demonstrated in order to obtain detailed insight into a gas-molecule collision that has not been studied in detail so far. The effective masses and phonon spectral densities of the monolayers seen by different projectiles are discussed based on classical models such as the hard cube model and the recently developed smooth surface model. Large effective masses are deduced for both the monolayers, suggesting collective effects of surface atoms in the single collision event. The effective Debye temperature of graphene was found to be similar to that reported in highly oriented pyrolytic graphite (HOPG), indicating that the graphene is decoupled well from the Pt substrate. A much smaller Debye-Waller factor was found for the C(60) layer, probably reflecting the strong C(60)-Pt(111) interaction.

Water adsorption on graphene/Pt(111) at room temperature: A vibrational investigation

“…The incidence angle has been set to 55 • with respect to the sample normal. The analysis of both LEED pattern and phonon modes show, in agreement with previous results, 32,37,42,43 a negligible interaction between MLG and the underlying Pt substrate. Accordingly, MLG may be considered as a quasi-freestanding sheet on Pt(111).…”

“…As demonstrated by in-situ low-energy electron microscopy, 30 no nucleation and growth of additional graphene sheets beyond the monolayer is possible on Pt(111). [30][31][32][33][34][35][36][37][38] The attained LEED pattern (shown in Figure 1) is essentially similar to that one reported in Ref. 32.…”

Probing interlayer interactions between graphene and metal substrates by supersonic rare-gas atom scattering

“…Nevertheless, if it is assumed that the mass M S is 12 amu, corresponding to the mass of a single carbon atom, the θ Dn values deduced from the slope of the Debye-Waller attenuation based on (1) are 1130 ± 50, 580 ± 70, and 480 ± 70 K for gr/Ru(0001), gr/Pt, and HOPG, respectively. These values of θ Dn agree with previous reports using the same technique [4,36,41]. Despite the ambiguity associated with determination of the crystal mass, it is clear that the θ Dn of gr/Pt(111) is similar in value to the HOPG within the uncertainty, but that of gr/Ru(0001) is significantly larger, approximately twice as large as that of the other two graphenes.…”

“…To determine the Debye temperature using Eq. (1), we used a "standard" value of the surface attractive potential well depth D of 16 meV, according to previous studies [4,11,41]. Note that, in Fig.…”

“…One of the few ideal probes for the investigation of fragile organic layers is supersonic rare-gas atomic beam scattering, in which the typical beam energy is in the range of ten to several hundred meV [1]. In particular, lowenergy elastic and inelastic He-atom scattering exhibits a high level of surface sensitivity and has been used for determining structural and vibrational properties of molecular adsorbates, which is not easy using other conventional techniques [2][3][4]. In this paper we use this sensitivity to obtain information about the weak interactions between substrates and a molecular overlayer through the detection of perpendicular vibrations of the molecular layer.…”