Substrate-mediated umklapp scattering at the incommensurate interface of a monatomic alloy layer

Abstract

Ultrathin Pb and Ge films deposited on Ag(111) surfaces have been investigated and compared. We found that at 1/3 ML, both films formed surface alloys, Ag 2 Pb and Ag 2 Ge, with √ 3 × √ 3R30 • and 19 20 √ 3 × 19 20 √ 3R30 • structures on Ag(111) but the surface electronic structures exhibit a most evident difference at the Ag(111) surface zone boundaryM Ag(111) , where the single band and the splitting ones were observed, respectively. Up to 1 ML, Ag 2 Ge subsequently develops into germanene with a striped phase and then a quasifreestanding phase, as previously reported [Lin et al., Phys. Rev. Mater. 2, 024003 (2018)], while Ag 2 Pb evolves to a dense Pb(111) phase that also reveals splitting bands atM Ag(111). We discover that the larger (smaller) atomic size of a Pb (Ge) atom with respect to an Ag atom causes the commensurate (incommensurate) interfaces and further demonstrate that the splitting bands of Ag 2 Ge surface alloy and 1-ML Pb film originated from the commonly incommensurate interface with Ag(111), which mediates umklapp scattering by inducing the mirror image of the pristine Ag 2 Ge and Pb(111) bands relative toM Ag(111) .

Optomechanical switching of adsorption configurations of polar organic molecules by UV radiation pressure

“…However for the case of the highest radiation flux (hereafter denoted as case 3), 5.22 × 10 13 photons/sec, the molecular-energy-state peak stays at about − 8.80 eV after a temperature increase to RT (blue curve), indicating a successful switch. As shown from the green EDCs, further post-annealing to 60 °C (green curve) makes the switch to Cl-up configurations for all three cases as expected 21 .

Figure 5 Photoemission spectra of 1-ML ClAlPc on Ag(111) crystal at the stages of before-irradiation, after-irradiation, post-annealed-to-RT, and post-annealed-to-60 °C at photon flux of ( a ) 3.14 × 10 13 photons/sec, ( b ) 4.18 × 10 13 photons/sec, and ( c ) 5.22 × 10 13 photons/sec.

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“…Post annealing to 60 °C drives case1 and case 2 to transit to the incomplete Cl-up configuration; both cases show similar increase in VL shift due to the existence of tilted configuration as indicated by the graphic illustration in the annotation for case1 and case 2. Yet the same treatment causes case 2’ to transform to the complete Cl-up configuration with negative VL shift as demonstrated in previous studies 12 , 21 due to the pushback effect. For case 3, the complete Cl-up configuration already formed at the after-irradiation stage, as implied by the almost statured large VL shift about 0.4 eV throughout the last three stages.…”

“…The Ag(111) crystal is chosen as the substrate for the organic molecule ClAlPc. The standard sputtering and annealing procedure was used to clean the sample 21 . The clean Ag(111) surface was confirmed by the LEED patterns and the sharp Ag Shockley surface state in photoemission spectra.…”

Resolving the structure of the striped Ge layer on Ag(111):Ag2Ge surface alloy with alternate fcc and hcp domains

“…On the contrary, we can exclude that this structure corresponds to a �19√3 × 19√3�𝑅𝑅30° reconstruction as proposed in ref. [11].…”

“…On the one hand, the striped phase has been interpreted as a highly stretched pure germanene layer, with 23% and 12% stretch in the direction parallel and perpendicular to the stripes [10]. On the other hand, in a recent study, the LEED diagram corresponding to satellite spots around diffraction conditions of a �√3 × √3� reconstruction, and previously attributed to the striped phase, has been interpreted as a �19√3 × 19√3�𝑅𝑅30° reconstruction, corresponding to a Ag2Ge surface alloy contracted by 5% with respect to the Ag(111) surface [11].…”